The impact of persisting herbicide residues on succeeding crops is of great concern to farmers because even the presence of very low concentrations can inhibit growth of crop and cause crop reduction. Furthermore, wastewater irrigation can lead to cadmium accumulation in soils. Thus, the co-occurrence of low amounts of herbicide residues and cadmium within agricultural fields are difficult to avoid. How the combination of these two pollutants affect plant metabolites remains to be elucidated and thus warrants investigation. Maize seeds were planted in soil that had been sprayed with chlorsulfuron and Cd, then we studied the effects of exposure to the herbicide chlorsulfuron (0.001, 0.003, 0.005, 0.008, and 0.010 mg kg^-1) and cadmium (as 5.0 mg kg^-1 CdCl₂) on maize seedlings by utilizing nuclear magnetic resonance (NMR) after 21 d. Principle component analysis of ¹H NMR spectra clearly discriminated between control and treatment groups. Compared with chlorsulfuron-only treatments, treatments using both contaminants showed higher content of phenolic acids, aspartic acid, choline, β-galactose, and α-glucose in the seedlings. Contrary to previous reports, we found larger pools of branched-chain amino acids in seedlings exposed to chlorsulfuron and CdCl₂. These findings indicate that CdCl₂ did not aggravate the effects of chlorsulfuron on maize seedlings metabolites. CdCl₂ elicited significant changes in plant metabolism at a concentration that did not impair plant growth. Moreover, chlorsulfuron did not inhibit branched chain amino acid synthesis.

To reveal the physiological and biochemical mechanism underlying graft union formation in pecan (Carya illinoinensis), dynamic changes in content of nutrients, tannin, and phytohormones together with key enzyme activities were investigated 0, 3, 5, 7, 10, 14, 18, 22, 31, and 40 d after grafting (DAG), in homograft unions. During graft union formation, peroxidase (POD) activity increased at 7 - 10 DAG compared with that at 0 DAG. Polyphenol oxidase (PPO) activity was higher in grafted than ungrafted pecan seedlings (control) at 22 DAG, which was similar to POD activity. The tannin content exhibited a decreasing trend with grafting relative to the control. Indole-3-acetic acid (IAA) and zeatin riboside (ZR) content increased from 7 - 10 DAG, with higher average content than in the control at 14 - 31 DAG. Abscisic acid (ABA), soluble sugar, starch, and soluble protein content was generally lower in grafted plants than in the control. Combined with our previous anatomical observations, these results suggested that, during graft development, some enzymes and growth promoting hormones might be required for callus proliferation at early stage and for vascular reconnection at the later stage. Nutrients provided energy for the whole graft development process. In contrast, some polyphenols and growth inhibiting hormones seemed to have negative effects on this process.

Aspects of plant growth such as height, branch number, leaf number, leaf area, pod area, 100-seed mass, etc., were correlated with biochemical changes such as contents of chlorophyll (Chl), proteins, DNA, and RNA, and protease activity during development and senescent phases in leaves, flowers, and pods of Cajanus cajan L. cv. UPAS-120 after treatments with kinetin (Kn). A significant increase was noticed in branch number, leaf number, leaf area, and seed mass while other growth processes registered a small increase after Kn application. Effectiveness of 5 µM Kn was also noticed in minimizing the loss of Chls, proteins, and nucleic acids as well as reducing the protease activity during maturity and senescence. Chl a/b ratio maintained a high value up to 30-d followed by a decline in leaves while flowers registered much lower ratio at 20-d-age. Pods were unique in having relatively lower ratio of Chl a/b in comparison to leaves.

The trihelix genes encode plant-specific transcription factors, which play a vital role in plant morphological and developmental processes. However, information about the presence of trihelix genes in sunflower (Helianthus annuus L.) is scarce. Sunflower belongs to composite family and possesses strong drought and salt-alkali tolerance. In this study based on H. annuus genome data, we have identified and analyzed the trihelix genes with a complete description of their physical and chemical properties, phylogenetic relationships, motif composition, chromosome distribution, exon-intron structure, cis-acting elements, and chromosome collinearity. In H. annuus, 31 full-length trihelix genes were identified and categorized into six subgroups (SIP, GT1, SH4, Gδ, GT-γ, and GT2). Multiple Em for motif elicitation (MEME), used for conservative motif analysis, identified 10 distinct motifs unevenly distributed on 31 trihelix genes. In addition to that, chromosome localization analysis showed the number and distribution of these trihelix genes on 17 chromosomes of H. annuus. Transcriptional structure analysis revealed the structure of introns and exons of different gene members. Furthermore, cis-element analysis identified 19 different types of cis-elements mainly related to abiotic stress, hormones, and growth and development of plant. Results of this study manifested novel insights into phylogenetic relationships and possible functions of H. annuus trihelix genes. Moreover, these findings can assist in future studies regarding specific physiological effects of H. annuus trihelix transcription factors.

Growth parameters (seedling elongation, fresh and dry masses) and protein content of Cucumis melo were enhanced by juglone (allelochemical occuring in the walnut family) treatment in pregerminative stage but decreased in postgerminative treatment. Catecholase and tyrosinase activities were also increased in both treatments. Xylem vessel radius of stem was enhanced significantly by the pregerminative treatment, whereas it decreased slightly by the postgerminative treatment. However, bundle radius of stem was enhanced by both treatments of juglone. Stomata length and number were not changed significantly. Xylem vessel radius of the stem was affected by juglone more than the other parameters.

Caffeine (1,3,7-trimethylxanthine) is purine alkaloid, and it is secondary metabolite produced naturally in plants. It plays a crucial role in defense and stress tolerance. A hydroponic experiment was carried out to study the morphological, biochemical, and ultrastructural effects of caffeine treatment on seedlings of tobacco (Nicotiana tabacum L. cv. Turkish). The plants were grown in a growth chamber for 14 d in Hoagland's nutrient solution supplemented with 0 (control), 25, 50, 100, 1000, and 5000 μM caffeine. Shoot heights as well as root lengths significantly decreased in the plants treated with 1000 and 5000 μM caffeine. Total protein and sugar content in leaves increased significantly in the 5000 μM caffeine-treated plants. Moreover, electron microscopic analysis shows that in plants exposed to 1000 and 5000 μM caffeine, mesophyll cells possessed enlarged chloroplasts with disrupted thylakoid membranes associated with large starch grains and plastoglobules. Scanning electron micrographs exhibit that the vast majority of stomata in the plants treated with 1000 and 5000 μM were closed. In contrast, the 25 and 50 μM caffeine-treated plants showed an enhanced growth and no signs of injury.

Licorice (Glycyrrhiza glabra L.) is an important medicinal plant accumulating high-value secondary metabolites. Real-time reverse transcription quantitative PCR (RT-qPCR) has become a common method for studying gene expression, and the availability of stable reference genes is a prerequisite to obtain accurate quantification of transcript abundance. Therefore, an experiment was designed to determine appropriate reference genes for gene expression studies in licorice. Based on reports in the literature and the availability of genomic sequences, eight putative reference genes were chosen. Further, the expression stabilities of these genes were evaluated in leaf and root tissues under normal and drought stress conditions using three distinct statistical algorithms including geNorm, NormFinder, and BestKeeper. Among the investigated genes, ubiquitin-conjugating enzyme E2 (UBC2), elongation factor 1 α (EF1), and actin (ACT) under normal conditions and ACT, β-tubulin (BTU), and UBC2 under drought stress conditions were the most stable genes in leaves, whereas BTU, ACT, and UBC2 under normal and drought stress conditions were identified as the most stable genes in roots. Nevertheless, the use of glyceraldehyde-3-phosphate dehydrogenase, F-box protein, and BTU have not been approved as reference genes for RT-qPCR data normalization. The findings in this study highlight the importance of the use of well-validated reference genes to the success of gene expression analysis using RT-qPCR.

We tested the capability of plants to utilize a mixture of amino acids and peptides as the exclusive source of nitrogen. The aim of this study was to find out how such a nutrition affected plantlet growth, photosynthetic performance, and N assimilation metabolism in tobacco (Nicotiana tabacum L., cv. Petit Havana SR1) grown in vitro. Plantlets grown in a casein hydrolysate-supplemented (CA) medium were compared to plantlets grown in a complete Murashige-Skoog (MS) medium, plantlets grown in an ammonium-deficient medium (N1), or plantlets grown in a nitrate-reduced medium (N2). In addition, the plantlets were grown in the presence or absence of 1.5 % (m/v) saccharose as an additional carbon source. Casein hydrolysate, similarly as inorganic N limitation, reduced generally plantlet growth, whereas no significant effects were observed on photosynthetic parameters evaluated by chlorophyll a fluorescence. Although addition of saccharose stimulated the plantlet growth particularly in the MS, it showed a rather negative influence both on the growth and on the photochemical efficiency of photosystem II in the plantlets grown in the CA and N1. The activities of enzymes involved in N assimilation, such as nitrate reductase (NR) and glutamine synthetase (GS), were lower in the plantlets grown in the CA, N1, and N2, both in leaves and in roots. On the other hand, glutamate synthase and glutamate dehydrogenase were employed by the plantlets grown in the CA. The presence of saccharose in the growth medium stimulated mainly NR and GS activities in the MS grown plantlets, whereas enzyme activities of the plantlets grown on the N1, N2, and CA were not significantly influenced. We proved that the tobacco plantlets can utilize casein hydrolysate as the sole source of N particularly during their photoautotrophic cultivation. Contrary to positive effects of photomixotrophic nutrition for the MS grown plantlets, exogenous sugar seemed to diminish the ability of the casein hydrolysate-supplemented plantlets to utilize efficiently the additional C source.

Leaves from 14-d-old Capsicum annuum L. cv. Anaheim seedlings were cultured on Murashige and Skoog (MS) medium containing different combinations of indole-3-acetic acid (IAA) and 6-benzyladenine (BA). After 3 months, cultures were transferred to new medium where BA was replaced with 9 μM isopentenyladenine (2iP) to enhance the growth of shoot buds. Developing shoots were elongated and rooted on MS medium enriched with 9 μM indole-3-butyric acid (IBA). All cultures were maintained in 250 cm³ baby jars covered with a clear polypropylene lid with or without microporous polypropylene membrane. Vessel type and plant growth regulators significantly affected callus morphogenic appearance, organogenesis and in vitro plantlet growth. Ventilated vessels supported photomixotrophic culture and improved regeneration and growth of plantlets. Higher plantlet dry mass and content of photosynthetic pigments, and lower stomatal density of plantlets grown in ventilated than in non-ventilated vessels facilitated ex vitro acclimation and growth.

Reverse transcription quantitative PCR is a widely used method to detect gene expressions. To obtain accurate expression results, the selection of proper reference genes is important and necessary. However, related works concerning reference gene selection have not been carried on many plant species, especially endangered ones. The aim of the present study was to select dependable reference genes for expression normalization of an endangered plant species with medicinal and ornamental value: Sinocalycanthus chinensis (Calycanthaceae). Nine reference genes with stable expressions were chosen for further analysis according to transcriptomic sequencing data from S. chinensis. The expression stability of these candidate genes in inner and outer petals at different floral developmental stages and in many different tissues was then analyzed with the geNorm and NormFinder software. The reference genes were evaluated by normalizing the expression of the anthocyanidin synthase gene in the outer and inner petals at different floral developmental stages to further verify the expression stability of these genes. Elongation factor 1-alpha (ScEF) and 50S ribosomal protein L27 were found to be the two most stable genes in the overall ranking of all the samples and different tissues. Furthermore, ScEF and protein phosphatase 2A were stably expressed in all petal samples. Moreover, among the nine candidate reference genes, phosphoglycerate kinase performed poorly in all sample sets. Our results will help to obtain reliable expression data in molecular studies of S. chinensis.

Cytosine methylation plays an important role in plant development by regulating gene expressions. However, few studies have investigated methylation changes during the tissue differentiation and development of perennial plants. Here, the fluorescence-labeled methylation-sensitive amplified polymorphism method was used with eight primer combinations to detect methylation in leaves and xylem obtained at the stages of inflorescence emergence (IE), ovary start growth, and fruit maturity (FM) in two pecan (Carya illinoinensis) cvs. Pawnee and Stuart. The results show that the total methylation in the xylem was generally higher than in the leaves at each stage. Substantial methylation variations were observed at the amplified sites in pecan tissues at the various stages. The methylation patterns changed between the leaf and xylem, with frequencies from 44.97 to 67.01 % over the three stages in the two cultivars, among which the variation frequency between the tissues at the FM stage was the highest for each cultivar. The frequencies of methylation variation between the leaf samples at any two stages ranged from 31.86 to 45.88 %, with higher variation frequencies between the xylem samples (40.90 - 59.44 %) for each cultivar, which is consistent with the comparative results of polymorphism rates between the leaf and xylem over the three stages. Cluster analysis and principal coordinate analysis suggest that the xylem at the IE and FM stages had relatively distant epigenetic relationships with other tissue samples as a whole. This study reveals the patterns of methylation variation and methylation relationships among pecan tissues undergoing different developmental processes, implying the important roles of methylation in tissue differentiation and development of trees. These results lay a theoretical foundation for elucidating the regulatory mechanisms of methylation involved in tree development.

Morphological traits of seeds of Festulolium braunii (K. Richt.) A. Camus cultivars were studied in relation to weather conditions. The obtained results show that morphological traits of seeds varied among cultivars and years of cultivation. The values of seed characteristics were higher in year 2016 due to more favorable weather conditions for plant growth. It was found that the husked seeds of Festulolium cultivars were characterized by a similar length and width regardless of the year, whereas naked seeds significantly differed in these characteristics. Mean values (from the research years) of seed parameters, such as thousand seed mass, area, convex area, shape factor, rectangle, as well as naked seed width showed variations among cultivars. At the same time, it was found that the mass of 1 000 seeds of individual cultivars showed the smallest variability in both years of the study (2.56 - 4.86 %) indicating a high stability of this trait. Thousand seed mass was significantly correlated with husked seed length / husked seed width ratio and husked seed length, and weakly correlated with yield.

Gibberellins (GAs) regulate diverse aspects of growth and development, but their role in root development and lateral root (LR) formation is poorly understood. In this study, GA₃ was applied to soybean [Glycine max (L.) Merr] by seed soaking. The results showed that root length and root surface area were significantly inhibited in early stages after GA₃ treatment. Microscopic examination showed that GA₃ treatment changed the cortex thickness, the pericycle diameter, and cell size in main root. Interestingly, exogenous GA₃ increased the quantity of lateral root primordia (LRP), but LR number decreased in this period. Moreover, the content of GAs, auxin and abscisic acid in root was altered. RNA-seq results revealed that application of GA₃ not only changed the expression of genes in GA biosynthesis pathway, including GA20ox and GA2ox, but also the GA regulation genes and signalling pathway genes. The changes in expression of gene concerning other hormones were also detected. In addition, GA₃ altered cell wall biogenesis and degradation genes which might be related to the changes of root morphology. In response to increased GA₃, 103 transcription factors were detected. Thus, exogenous GA₃ changed the content of hormones in roots and affected the root development by regulating the expression of respective genes.

The effects of exogenous nitric oxide (NO) and ethylenediaminetetraacetic acid (EDTA) on cadmium toxicity and accumulation in ryegrass (Lolium perenne L.) were studied in a hydroponic experiment. The results show that in plants without Cd application, addition of EDTA and sodium nitroprusside (SNP, an exogenous NO donor) significantly reduced the plant height, root length, and root activity of ryegrass, and significantly increased the O₂^*- generation rate and H₂O₂ and malondialdehyde (MDA) content in the aboveground and underground parts of ryegrass. Cadmium stress significantly inhibited ryegrass growth. Addition of SNP or EDTA alleviated Cd toxicity, and addition of both had a better effect. Compared with Cd alone, the shoot height and root length in the Cd+EDTA+SNP treatment increased by 68.8 and 59.6 %, and plant fresh and dry masses by 62.6 and 60.0 %, respectively. Also, the superoxide dismutase activity in the shoots and roots increased by 32.5 and 67.6 %, the peroxidase activity by 49.8 and 67.6 %, the ascorbate peroxidase activity by 134 and 102 %, the MDA content decreased by 30.4 and 21.8 %, and the O₂^*- generation rate by 29.0 and 26.1 %, respectively. At the same time, Cd content in the shoots and roots increased significantly by 89.7 and 30.2 %, respectively. Overall, the results suggest that exogenous NO could enhance Cd tolerance of ryegrass, but addition of EDTA could promote plant Cd uptake. Combined application of NO and EDTA increased Cd accumulation in the aboveground parts of ryegrass. In this experiment, the treatment of 100 µM CdCl₂ + 0.25 mM EDTA + 50 μM SNP showed the best effects in promoting Cd accumulation in ryegrass and enhancing its Cd tolerance.

Temperature is an important factor for growth, development, productivity and geographical distribution of many plants (Nahar et al. 2015). Chilling stress is a major abiotic stress of crop production in Northeast China. Chilling stress exposure has been shown to enhance production of reactive oxygen species (ROS) and oxidative stress occurs (Nahar et al. 2015). The ROS, which include superoxide radical (O₂^*-), hydrogen peroxide (H₂O₂), hydroxyl radical (.OH), and singlet oxygen (¹O₂), cause damage to structural proteins, nucleic acids, enzymes, cell membranes, and other essential molecules involved in plant metabolism (Sharma et al. 2012, Nahar et al. 2015). Plants have developed mechanisms to tolerate environmental stress conditions through various physiological adaptations, including non-enzymatic and enzymatic ROS scavenging pathways (Hossain et al. 2010, Sharma et al. 2012, Nahar et al. 2015). Non-enzymic components of the antioxidative defense system include reduced ascorbate (AsA) and reduced glutathione (GSH) as well as osmotic adjustment substances as proline, soluble sugars, and soluble proteins which protect membrane integrity and cellular components from dehydration (Özlem and Ekmekçi 2011). The enzymatic antioxidants comprise superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX), glutathione reductase (GR), etc. (Gill and Tuteja 2010, Hossain et al. 2010). These enzymes, through step-by-step reaction, scavenge ROS with AsA and GSH as electron acceptors (Gill and Tuteja 2010). Nahar et al. (2015) has established that low temperature stress increased H₂O₂ and MDA content. Exogenous spermidine (Spd) in low temperature treatment increases the content of AsA and GSH, decreases the content of oxidized ascorbate (DHA) and oxidized glutathione GSSG, and improves activity of APX and GR. Various strategies are being employed in order to minimize the adverse effects of environmental stresses in plants. Exogenously applied plant growth regulators (PGRs) is an effective, facile, and practical technique to enhance tolerance of crops, and this approach has been used widely in recent years. One of the PGRs is 5-aminolevulinic acid, or 5-amino-4-oxo-pentanoic acid (ALA), which has a relative molecular mass of 131, and it is an essential precursor of tetrapyrrole compounds including chlorophyll, heme, and phytochrome (Balestrasse et al. 2010) and its formation may be the rate limiting step. Hotta et al. (1997a,b) observed that low dosage of ALA has plant growth regulator properties, such as promoting chlorophyll biosynthesis and enhancing photosynthesis (Memon et al. 2009), responding to environmental stresses (Korkmaz and Korkmaz 2009, Korkmaz et al. 2010, Zhang et al. 2012, Dan et al. 2013, Fu et al. 2016), and promoting recovery of growth after herbicide applications (Zhang et al. 2008). High dosages of ALA can cause the accumulation of several chlorophyll synthesis intermediates, but also production of ROS leading to oxidative stress (Balestrasse et al. 2010). Materials and methods Plants and chilling stress: Mung be

Cellulose is the most abundant polysaccharide produced by plants. In the form of rigid microfibrils surrounding the cells, cellulose constitutes the load-bearing cell wall element that controls cell growth and shape. Cellulose microfibrils are laid down outside the cell by the multimeric plasma membrane-inserted cellulose synthase complexes (CSCs), which move along underlying cortical microtubules (CMTs). In plants, CSCs are shaped as rosettes with six lobes symmetrically arranged in a hexagonal structure. In Arabidopsis, the CSC is composed of at least three functionally non-redundant cellulose synthase (CESA) glycosyltransferases in both primary and secondary cell walls. The number, organization, and interactions of CESA proteins within the CSC have been debated for many years on the basis of numerous lines of evidence provided by electron microscopy, biochemical and genetic approaches, spectroscopic techniques, as well as computational modeling. The Arabidopsis thaliana model was extremely useful in elucidating the molecular composition of CSC and enabled to elucidate the specialized functions of distinct AtCESA isoforms. Several additional, non-CESA proteins involved in cellulose synthesis and its regulation were also identified in Arabidopsis. This review outlines the latest findings on CSC organization, trafficking, and plant-specific proteins directly associated with the complex and interconnecting CESAs with CMTs.

Melatonin (N-acetyl-5-methoxytryptamine) is an essential molecule which regulates plant growth and development and alleviates the damaging effects of abiotic stresses. To evaluate the important functions of melatonin in response to salinity stress, the effects of exogenous melatonin on the antioxidant system and growth of tomato (Solanum lycopersicum L.) under 150 mM NaCl stress were investigated. The application of 100 μM melatonin compensated the growth inhibition caused by salt-stress. Melatonin treated seedlings had an increased fresh and dry masses of shoots and roots. The application of 1 - 200 µM melatonin notably enhanced the relative chlorophyll content (SPAD index), root characteristics, and gas exchange in tomato seedlings subjected to salt stress compared to seedlings treated with salt stress alone. Moreover, melatonin pretreatment minimized accumulation of reactive oxygen species and improved activities of antioxidative enzymes including catalase, superoxide dismutase, glutathione reductase, and ascorbate peroxidase.

Drought resistance in plants can be associated with four different strategies to cope with water stress. These strategies are classified as drought escape, avoidance, tolerance, and recovery. The expression of each strategy depends on plant species and its genetic potential, but also on the environmental conditions, including the stress intensity and duration. Often, prolonged drought conditions are associated with drought escape or avoidance, whereas short but severe drought periods induce drought tolerance. To analyze the components of drought resistance in forage grasses, we applied two Lolium multiflorum/Festuca arundinacea introgression forms into a comprehensive research. Obtained results clearly show that the response of plants to severe short term drought conditions with limited rhizosphere did not reflect their response to long progressive drought conditions, which did not limit root growth. The BC4-INT-40 introgression form with extensive and deep roots was characterized by a more efficient drought avoidance and regeneration mechanisms under long-term drought, whereas the BC4-INT-66 form with shorter roots revealed a lower productivity and re-growth capacity under the prolonged drought. On the other hand, this form had also a better photosynthetic performance under short and intensive drought conditions with a limited space for root development.

Festulolium cultivars are widely utilized in Lithuania because they are persistent under abiotic stresses and are high yielding. However, changing climate challenges the existing Festulolium cultivars to adapt to new growing conditions and still maintain the yield. In this study, we aimed at evaluating the yield stability of two Festulolium cultivars in field trials under fluctuating Lithuanian conditions. The mean total dry matter yield (DMY) of both Festulolium cultivars fluctuated greatly between the years and ANOVA analysis showed a significant effect of environment on total DMY as well as DMY of each cut, but the genotype × environment interaction was not significant. There was a high difference between the total DMY of 1^st year and 2^nd year of use of plots in each year of observation. The highest DMYs were harvested in the years 2015 and 2016. Dry matter yield of the 1^st cut was the largest component of the total DMY for most of the years. The plants overwintered the first winter after sowing very well over the whole study period, resulting in excellent spring growth. The winter survival scores of 2^nd year of use of plots were lower than 1^st year of use and strongly correlated with the 1^st cut DMY of 2^nd year of use (r = 0.81). Spring growth of plants at 2^nd year of use was poorer, the correlation between winter survival and spring growth of 2^nd year of use was 0.62. The scores of regrowth after the cuts of 1^st and 2^nd years of use were very similar for most of the experimental years and moderately correlated with the sum of DMYs after cuts (r = 0.55 and r = 0.5, respectively).

Late embryogenesis abundant (LEA) proteins are important for abiotic stress tolerance in diverse organisms. Within the LEA protein superfamily, group 4 members are characterized by a conserved N-terminal region and a structurally disordered C-terminal region that varies regarding length and amino acid content. Previous in vitro assays have suggested that the conserved N-terminal region shared by group 4 LEA proteins is critical for forming an amphipathic α-helix and protecting enzymatic activities from the adverse effects of desiccation or freezing. However, the cellular roles of the varying C-terminal region remain largely to be characterized. Medicago truncatula contains five subgroup LEA4B proteins encoding loci of which three are tandemly arranged on chromosome 7 due to local gene duplication events. In this study, abiotic stresses and addition of abscisic acid (ABA) induced the transcription of the four LEA4B genes. Escherichia coli cells overexpressing the three tandemly aligned LEA genes indicated significantly increased tolerance to salt, osmotic, heat, and freezing stresses. However, the extent of the protective effects on the survival and growth of bacterial cells differed among the LEA proteins, potentially because of variations in the C-terminal region. This possibility was further supported by the observation that the protective effects of the native truncated MtLEA3140, which only contains a conserved N-terminal region, were inferior to the effects of the full-length mutant version. The results suggest that the structurally flexible C-terminal region of group 4 LEA proteins plays roles in protecting cells from damages caused by various abiotic stresses, and provide clues for elucidating the mechanisms underlying the intracellular functions of these proteins.

London plane (Platanus acerifolia Wild.) is a famous landscape plant because of its numerous desirable traits except the abundant pollens and seed hairs, which not only pollute the environment but also affect human health. To resolve these problems, we herein isolated and functionally analyzed the promoter of PlacSEP1.1, an orthologous gene of Arabidopsis SEPALLATA1, and investigated the potential usability for cell ablation strategies to engineer reproductive sterility in plants. A 2130 bp 5' upstream region of PlacSEP1.1 was isolated and termed pPlacSEP1.1. Putative motif detections show that there were several types of motifs in pPlacSEP1.1 including core promoter elements, tissue-specific expression regulatory elements, and some negative regulatory elements. β-Glucuronidase histochemical and quantitative assay showed that pPlacSEP1.1 of all deletions was active in all detected tissues except the shortest deletion D5 in roots. In order to test whether pPlacSEP1.1 could be used for London plane sterility breeding with a cytotoxic gene Barnase, the pPlacSEP1.1::Barnase and pPlacSEP1.1::Barnase-mic35S-Barstar vectors were constructed and transformed into tobacco. The pPlacSEP1.1::Barnase transgenic tobacco showed serious defects with respect to vegetative development and died within a couple of weeks after transplantation. On the other hand, most pPlacSEP1.1::Barnase-mic35S-Barstar transgenic tobacco showed normal vegetative growth and inflorescence, and flower development prevented phenotype.

γ-Aminobutyric acid (GABA) regulates plant tolerance to abiotic stresses; however, a transcriptomic change and key stress-related genes induced by GABA have not been investigated in plants during a prolonged period of salt stress. Roots of creeping bentgrass (Agrostis stolonifera) cv. Penncross were pretreated with or without 0.5 mM GABA solution for 2 days and then subjected to salt stress for 20 days (150 mM NaCl solution for 3 d, 200 mM NaCl for another 3 d, and 250 mM NaCl for 14 d) in controlled growth chambers. The application of GABA significantly increased GABA content in roots and alleviated a salt-stress induced decrease in GABA content in leaves. This was associated with a significant increase in salt tolerance as demonstrated by a significantly higher leaf relative water content, photochemical efficiency, performance index on absorption basis, and lower electrolyte leakage in GABA-pretreated plants as compared to untreated plants under salt stress. Transcriptomic analysis found that GABA-induced salt tolerance was closely associated with saccharide, amino acid, and lipid metabolism. The GABA upregulated key differentially expressed genes including cytochrome P450 (CYP450), zinc transporter 29 (ZTP29), alpha-amylase 3 (AMY3), 3-ketoacyl-CoA synthase 6 (KCS6), aldehyde oxidase (AO), acetyl-CoA carboxylase 1 (ACC1), and magnesium-chelatase (Mg-CHT) involved in zinc homeostasis, starch degradation, and the biosynthesis of wax, fatty acid, chlorophyll, and abscisic acid, which could contribute to GABA-regulated salt tolerance. Current findings prove that GABA application is an efficient approach to enhance salt tolerance of creeping bentgrass during a prolonged period of salt stress and also provide valuable information to better understand key candidate genes and regulatory pathways of GABA-induced salt tolerance in plants.

Heat stress is one of the most crucial factors affecting crop growth and productivity worldwide. So, searching for a potent eco-friendly heat stress alleviator is the main issue nowadays. The current study was conducted to assess the ameliorative effects of 1.5 mM potassium silicate (K₂SiO₃, further only Si) or 1.66 mM silicon dioxide nanoparticles (SiNPs) on wheat (Triticum aestivum L.) seedlings exposed to heat stress (45 °C, 4 h). The observations show that Si or SiNPs treatments significantly restored the heat stress-provoked ultrastructural distortions of cellular organelles, particularly chloroplasts and the nucleus. Further, both Si and SiNPs enhanced the photosynthetic capacity as revealed by increments in the photochemical efficiency of photosystem II and the performance index as well as the content of photosynthetic pigments. A reduction in malondialdehyde accumulation in Si and SiNPs treated plants was positively related to their membrane stability index. The reverse transcription PCR analysis showed that Si treatment but not SiNP treatment stimulated the overexpressions of both Triticum aestivum plasma membrane intrinsic protein (TaPIP1) and Triticum aestivum nodulin 26-like intrinsic protein (TaNIP2) aquaporin genes parallelly with an improvement in the relative water content. This investigation reveals that Si was more effective than SiNPs in restoring the heat stress injuries. To the best of our knowledge, this is the first investigation exploring the effects of Si and SiNPs in improving thermotolerance of wheat seedlings.

The variegated leaves of Actinidia polygama exhibit a striking colour change during development. However, little is known whether the photosynthetic capacity of white leaves can be maintained. Therefore, spectrum properties, leaf structure, net photosynthetic rate (P_N), and chlorophyll fluorescence in the green and white leaves were investigated. Although reflectance at 400 - 700 nm in white leaves was higher than that in green leaves, total chlorophyll content of white leaves was similar to that in green leaves. Palisade tissue cells of white leaves contained functional chloroplasts. Large intercellular spaces were observed between the epidermal and mesophyll cells and within the palisade tissue cell layer in white leaves. Both P_N and the actual quantum yield of photosystem II in white leaves were similar to green leaves. At different leaf growth stages, P_N of white leaves was about 88 - 100 % of the P_N of green leaves. The efficiency of electron move beyond Q_A^- (ET/TR) and the quantum yield of electron transport (ET/ABS) in white leaves was higher than in green leaves. In conclusion, photosynthetic capacity in white leaves of A. polygama showed two favorable characteristics during the whole sampling period: 1) despite a higher spectral reflectance in white leaves, P_N of white leaves remained relatively high compared with green leaves; 2) the higher activity of photosystem II of white leaves enabled photosynthetic capacity maintenance.

We investigated the effect of sulfur (S) supply on growth, oxidative stress, and iron uptake and transport in rice (Oryza sativa L.) seedlings using a hydroponic culture with four S concentrations (0, 1.75, 3.5, and 7.0 mM). The length and fresh mass of seedlings were enhanced with the increased S concentration. In addition, the content of thiobarbituric acid reactive substances (TBARS) in rice leaves was the highest when no S was added to the nutrition solution and gradually declined with the increasing S supply. The higher S nutrition reduced the amount of Fe plaque on rice roots and increased Fe content in roots and leaves. The content of nicotianamine was significantly higher in rice roots under the S deficiency, whereas the reverse trend was observed in rice shoots. Taken together, the sufficient S nutrition promoted growth of rice, reduced oxidative stress, and ensured normal Fe uptake and distribution.

Worldwide, a relevant surface of arable lands is facing salt stress, and this surface is increasing continuously due to both natural and anthropogenic activities. Nitric oxide (NO) is a small, gaseous molecule with a plethora of physiological roles in plants. In addition to its normal physiological functions, NO protects plants subjected to different environmental cues including salinity. For example, NO mediates photosynthesis and stomatal conductance, stimulates the activity of Na⁺/H⁺ antiport in tonoplast, promotes the biosynthesis of osmolytes, and counteracts overaccumulation of reactive oxygen species in plant cells under salt stress. Exogenous NO is also beneficial for plants subjected to salinity, in which it increases salinity tolerance via growth promotion, reversing oxidative damage, and maintaining ion homeostasis. This review provides a comprehensive picture of the NO-mediated mechanisms in plants, resulting in salinity tolerance with a particular focus on the photosynthetic processes, the antioxidant patterns as well as the cross-talk with other regulatory compounds in plant cells.

Appropriate choice of reference genes for data normalization is of critical importance for accurate real time reverse transcription quantitative PCR (RT-qPCR) analysis of gene expression. Oat is an agriculturally important crop cultivated widely around the world for grain or forage, and appropriate reference genes for reliable gene expression analysis remain to be identified. In this study, we selected nine candidate reference genes based on available oat RNA-seq data. We then conducted a systematic evaluation of the relative expression stability of these genes in different tissues and under salt stress using statistical algorithms, geNorm, NormFinder, and BestKeeper. Our findings reveal that the highest-ranked reference genes for accurate data normalization should be selected according to specific sample subsets. For different tissues, the combination of two reference genes [elongation factor 1-alpha (EF1α) and serine/threonine protein phosphatase 2] was sufficient for accurate normalization. For salt stress treatment, the combination of two reference genes (EF1α and TATA-binding protein) was sufficient for accurate normalization. Moreover, the commonly used reference genes, actin and glyceraldehyde 3-phosphate dehydrogenase, were least suitable for data normalization of oat samples. Expression of a salt stress-inducible transcription factor Avena sativa WRKY2 was investigated to validate the reference genes identified in this study. This is the first systematic study of reference gene selection in cultivated oat and provides guidelines to obtain more accurate RT-qPCR results in this species.

Columnar apple is a valuable resource for genetic improvement of cultivated apples due to its special tree architecture. Strigolactones (SLs) are a novel class of plant hormones controlling shoot branching. The content of SLs is higher in columnar apple than in standard apples. In this study, the members of major gene families involved in SLs biosynthesis and signaling were identified from apple genomic sequences and their expression profiles were characterized in columnar and standard apples using reverse transcription quantitative polymerase chain reactions. In comparison with standard apple, the higher expressions of MORE AXILLARY GROWTH genes MdMAX3-1 and MdMAX4-4 were detected in both buds and shoots of columnar apple but the expression of DWARF gene MdD53-4 showed a lower expression in columnar apple. Overexpression of Columnar gene MdCo31 in tobacco increased SLs content and weakened the inhibition of SLs signal transduction by increasing expression of MAX3 and down-regulating the transcription of D53. Thus MdCo31 could be a strong candidate gene for the control of columnar habit.

To clarify the effects of the introduction of Festuca pratensis-derived genomic regions in a tetraploid Lolium perenne genomic background, we analyzed quantitative trait loci (QTLs) for winter hardiness and eight other agronomic traits using two mapping populations generated by sequential backcrosses of two different amphiploid F. pratensis × L. perenne hybrids to tetraploid L. perenne. We constructed two interspecific linkage maps: FLBC2A (143 DNA markers, 301.2 cM total) and FLBC2C (126 markers, 256.2 cM), based on F. pratensis-derived alleles, with 72 markers in common. Interval mapping detected QTLs for seven traits in FLBC2A and for six traits in FLBC2C. In both populations, QTLs for winter hardiness with a positive effect of the F. pratensis allele were detected around common markers on linkage group (LG) 1. In FLBC2A, other additional QTLs for winter hardiness with a positive effect of the F. pratensis allele were detected on LG4 and LG5, and one with a negative effect was detected on LG2. In both populations, a QTL for heading date was detected on LG7. Quantitative trait loci for vigor after planting and stubble width were detected on different LGs between populations. Quantitative trait loci for dry matter yield before winter, plant growth habit, inflorescence length, number of spikelets per inflorescence, and leaf width were detected in only one population. Population-dependent QTLs thought to be involved in intraspecific variation in addition to interspecific one. On the other hand, QTLs found in the two different populations could lead to the development of versatile markers for Festulolium breeding.

The calcineurin B-like protein (CBL)-interacting protein kinase (CIPK) complex is an essential calcium sensor and contributes to biotic and abiotic stress responses. However, citrus CBL and CIPK gene family members and their underlying roles during drought and arbuscular mycorrhizal fungi (AMF) colonization remain relatively unknown. In the present study, CBLs and CIPKs were characterized in Citrus sinensis by analyzing the presence of specific domains such as the elongation factor (EF)-hand motif in CBLs, and a protein kinase and an Asn-Ala-Phe domain in CIPKs. After mining the C. sinensis genome, we identified 8 CsCBLs and 17 CsCIPKs. Among these genes, three CsCBLs and nine CsCIPKs showed syntenic relationships with the Arabidopsis thaliana homologs AtCBLs and AtCIPKs, respectively. According to gene expression and cis-acting element analysis, all 8 CsCBLs and 16 CsCIPKs were expressed in the roots, where the regulation of expression was not consistent with their promoter cis-elements. Drought treatment remarkably downregulated the expression of CsCBL8 and upregulated CsCBL7, CsCIPK4, and CsCIPK7 expressions. The AMF colonization induced CsCBL4, 5, 6, and 7 as well as CsCIPK2, 4, 10, 11, 13, 14, and 16 expressions and repressed CsCBL1, 2, 3, and 8 and CsCIPK1, 3, 6, 8, 9, and 12 expressions. Based on the expression data and co-expression analysis, CsCBL1-CsCIPK1, CsCBL1-CsCIPK3, CsCBL1-CsCIPK6, and CsCBL1-CsCIPK9 showed the significant positive correlations to drought and AMF responses.