Iron availability affects plant growth depending on soil type. Mangroves are characterized by alkaline soils in which the halophytic wild rice relative Porteresia coarctata thrives. Young plants of P. coarctata grew optimally in the presence of 150 mM NaCl in a hydroponic medium and tolerated iron deficiency and salt up to 21 d without showing any symptoms of stress. A homolog of the rice iron deficiency responsive cis-acting element binding factor (IDEF1) that functions at the base of an iron regulated network was isolated and characterized from P. coarctata. PcIDEF1 had a close paralog in P. coarctata genome and its transcript expression was upregulated by both iron deficient conditions and salt treated conditions for up to three weeks. Sub-cellular localization study suggests nuclear targeting PcIDEF1 protein in guard cells and root tissues of tobacco. In vitro assays for metal binding affinity and binding PcIDEF1 to iron deficiency responsive element 1 (IDE1)-like elements in the 5' flanking region of an iron regulated transporter from P. coarctata suggest that PcIDEF1 could potentially sense iron content in a plant cell and regulate expression of iron responsive genes containing IDE1-like elements in their promoter region. This study provides evidence for a possible cross-talk between iron deficiency and salt responses.

Kochia sieversiana (Pall.) C.A. Mey. is a forage plant that can grow in extremely alkalinized grasslands at pH 10 or higher. Accumulation of a large amount of oxalic acid (OxA) is a primary characteristic of K. sieversiana. In our study, seedlings of K. sieversiana were exposed to the following conditions: non-stress, salinity (200 mM, a molar ratio of NaCl and Na₂SO₄ 1:1), and alkali stress (200 mM, a molar ratio of NaHCO₃ and Na₂CO₃ 1:1). Growth, water content, content of organic acids (including OxA), Na⁺, and K⁺, and activities of some OxA metabolism-related enzymes were determined. Results show that glycolate oxidase was the key enzyme for OxA synthesis; however, the carboxylation of phosphoenolpyruvate (PEP) by PEP carboxylase (PEPC) probably played a minor role in the OxA-synthetic pathway. The pathway of L-ascorbic acid catabolism was not the main source of OxA accumulation, and the activity of oxalate oxidase (OxO) involved in OxA decomposition was not a limiting factor for inner OxA accumulation. Taken together, accumulation of a large amount of OxA are not related to the degradation and secretion function of OxO but largely depend upon its synthetic function.

The present study evaluated the effects of chilling, partial desiccation, cotyledon excision and successive subculture of microspore-derived embryos on plant development in oilseed rape (Brassica napus L.). The results showed that out of the five media, all the genotypes showed the best response when the embryos were cultured on the half-strength Murashige and Skoog medium with 2.0 mg dm^-3 benzylaminopurine. A cold treatment for 3 or 5 d further increased frequencies of embryo germination (90.0 %) and plantlet development (58.46 %). Desiccation for one day also increased the embryo germination and plantlet development in all genotypes tested. Cutting the cotyledons of the embryos at late cotyledonary stage significantly increased the frequency of plantlet development. The highest rate of plantlet development was obtained from cultures of embryos sampled with size of less than 4.0 mm. The successive subculture further improved the germination and development of plantlets from embryos. In the genotype ZJU452, the rate of plantlet development reached 99.78 % after the second subculture of embryos.

We employed the comet assay (single cell gel electrophoresis) to evaluate induced DNA damage in nuclei isolated from tobacco leaves (Nicotiana tabacum var. xanthi) inoculated with Potato virus X (PVX). The highest DNA damage, expressed by the tail moment value, was observed in the inoculated leaves and decreased in the 1^st to 4^th systemic leaves. DNA damage increased with the time after the inoculation (from day 3 to day 21) and was higher in nuclei isolated from a part of the leaf at the petiole compared to nuclei isolated from the leaf tip. A Pearson moment correlation (r = 0.94) between the induced DNA damage and the PVX titres expressed by ELISA absorbance values was observed. The PVX infection did not induce a significant increase in the rate of somatic mutations evaluated by appearance of dark green, yellow, and double green/yellow sectors on the heterozygous pale green leaves of N. tabacum var. xanthi.

We investigated the effect of water stress on yield and quality of tomato plants overexpressing Solanum lycopersicum thylakoid-bound ascorbate peroxidase gene (StAPX). APX activity, hydrogen peroxide content, net photosynthetic rate of tomato leaves, and yield and nutrition quality of tomato fruits were measured under soil moisture 70, 60, and 50 % of full field capacity. Results show that the capability of APX for scavenging hydrogen peroxide induced by water stress was higher in the transgenic than the wild type (WT) plants. The yield of fruits of the transgenic tomato plants was higher than that of WT plants under water stress and the fruit nutrition quality was not different. These results indicate that overexpression of StAPX might improve water stress tolerance in the transgenic tomato plants.

Cytokinin (CK) content and activities of several antioxidant enzymes were examined during plant ontogeny with the aim to elucidate their role in delayed senescence of transgenic Pssu-ipt tobacco. Control Nicotiana tabacum L. (cv. Petit Havana SR1) and transgenic tobacco with the ipt gene under the control of the promoter of small subunit of Rubisco (Pssu-ipt) were both grown either as grafts on control rootstocks or as rooted plants. Both control plant types showed a decline in total content of CKs with proceeding plant senescence. Contrary to this both transgenic plant types exhibited at least ten times higher content of CKs than controls and a significant increase of CK contents throughout the ontogeny with maximal values in the later stages of plant development. Significantly higher portion of O-glucosides was found in both transgenic plant types compared to control ones. In transgenic plants, zeatin and zeatin riboside were predominant type of CKs. Generally, Pssu-ipt tobacco exhibited elevated activities of antioxidant enzymes compared to control tobacco particularly in the later stages of plant development. While in control tobacco activity of glutathione reductase (GR) and superoxide dismutase (SOD) showed increasing activity up to the onset of flowering and then gradually decreased, in both transgenic types GR increased and SOD activity showed only small change throughout the plant ontogeny. Ascorbate peroxidase (APOD) was stimulated in both transgenic types. The manifold enhancement of syringaldazine and guaiacol peroxidase activities was observed in transgenic grafts throughout plant ontogeny in contrast to control and transgenic rooted plants, where the increase was found only in the late stages. Electron microscopic examination showed higher number of crystallic cores in peroxisomes and abnormal interactions among organelles in transgenic tobacco in comparison with control plant. The overproduction of cytokinins resulted in the stimulation of activities of AOE throughout the plant ontogeny of transgenic Pssu-ipt tobacco.

Cotton (Gossypium hirsutum L.) net photosynthetic rate (P_N) decreased with leaf age and low irradiance, and the interaction of these factors might lead to decreased yields mainly in crops with a high plant density. Shade decreased leaf gas exchange, mainly in young leaves, which did not recover after exposure to an increasing irradiance. Old leaves reached P_N saturation at a lower irradiance than young leaves. Also stomatal conductance decreased with leaf age and shading. Intercellular CO₂ concentration and irradiance were inversely related. The responses of P_N to irradiance decreased as leaf aged, and it did not interact with shade suggesting that self-shading is not primarily responsible for the decreased photosynthetic rate in older cotton leaves.

Flow-sorted chromosomes have been used to simplify analyses of complex plant genomes. In bread wheat, majority of studies involve cultivar Chinese Spring, a genotype chosen for sequencing. Telosomic lines developed from this cultivar enable isolation by flow sorting chromosome arms, which represent less than 3.4 % of the genome. However, access to other wheat cultivars is needed to allow mapping and cloning useful genes. In these cultivars, cytogenetic stocks are not readily available and only one chromosome (3B) can be sorted. Remaining chromosomes form composite peaks on flow karyotypes and cannot be sorted. In order to overcome this difficulty, we tested a pragmatic approach in which composite chromosome peaks are dissected to smaller sections. The analysis of chromosome composition in sorted fractions confirmed feasibility of obtaining sub-genomic fractions comprising only a few chromosomes. Usually one of the chromosomes was more abundant and the frequencies of dominant chromosomes in sorted fractions ranged from 16 % (chromosome 7B) to 80 % (chromosome 2B). The enrichment factor, calculated as the relative proportion of chromosomal DNA in the wheat genome to the proportion of chromosomal DNA in a sorted fraction, ranged from 3.2-fold (7B) to 16.4-fold (5D). At least a 5-fold enrichment can be obtained for 17 out of 21 wheat chromosomes. Moreover, we show that 15 out of the 21 chromosomes can be sorted without being contaminated by their homoeologs. These observations provide opportunities for constructing sub-genomic large-insert DNA libraries, optical mapping, and targeted sequencing selected genome regions in various cultivars of wheat. The availability of fractions enriched for chromosomes of interest and free of contaminating homoeologs will increase the efficiency of research projects and reduce their costs as compared to whole genome approaches. The same methodology should be feasible in other plants where single chromosome types cannot be sorted.

ApKUPs are typical high-affinity potassium (K⁺) transporters of Alternanthera philoxeroides which are involved in its response to K⁺ starvation and abiotic stresses. In this study, the overexpression of ApKUP3 gene in rice resulted in enhanced K⁺ nutrition and drought tolerance of transgenic plants. Compared with wild-type (WT) plants, the transgenic plants showed a better growth performance and a strengthened K⁺ accumulation under different K⁺ supplies. The ApKUP3 overexpression in the rice plants also enhanced tolerance to a drought stress, as evidenced by a reduced leaf water loss and an increased total leaf chlorophyll content, stomatal conductance, net photosynthetic rate, and activities of superoxide dismutase, peroxidase, and ascorbate peroxidase (APX). Moreover, the transcription of genes involved in the antioxidation defense system were higher in the transgenic plants than in the WT plants upon the drought stress.

To investigate whether exogenous sucrose can protect cucumber from water stress, cucumber (Cucumis sativus L.) seedlings were pretreated with 90 mM sucrose or 90 mM mannitol for 1 d and then were dehydrated with 10 % (m/v) polyethylene glycol (PEG) 6000 for further 1 d. Dehydration inhibited plant growth and decreased osmotic potential and relative water content (RWC) in leaves. The pretreatment with 90 mM sucrose further reduced the osmotic potential but increased the RWC and alleviated the growth inhibition. Compared with the PEG treatment alone, the combination of sucrose + PEG increased the activities of superoxide dismutase, guaiacol peroxidase, glutathione reductase, dehydroascorbate reductase, monodehydroascorbate reductase, ascorbate peroxidase, and glutathione peroxidase, and elevated the content of endogenous sucrose, glucose, and fructose together with the activities of soluble acid invertase and neutral invertase. This was in accordance with the enhanced transcription of genes encoding copper/zinc superoxide dismutase, guaiacol peroxidase, and glutathione reductase. Furthermore, the sucrose pretreatment decreased the content of malondialdehyde and hydrogen peroxide and increased the content of ascorbate, reduced glutathione, and proline under the dehydration. Taken together, the pretreatment with 90 mM sucrose, but much less with mannitol, induced antioxidants, proline, and soluble sugars and thus reduced dehydration-caused damage to the cucumber seedlings.

Jatropha curcas L. is a plant with various commercial uses, and drought is an important limiting factor for its distribution and production. In this study, we investigated the role of drought hardening in an increased drought tolerance in J. curcas, and the involvement of osmoregulation and biochemical pathways in this enhanced tolerance. Results show that a drought hardening treatment with 10 % (m/v) polyethylene glycol 6000 for two days significantly increased a survival rate, decreased the content of malondialdehyde, and alleviated electrolyte leakage in the J. curcas seedlings under the drought stress. Measurements of leaf water potential, osmotic potential, and pressure potential show that this drought hardening treatment can improve the water status of J. curcas seedlings during the early phase of drought stress. In addition, the drought hardening treatment gradually increased the concentrations of compatible solutes proline, glycinebetaine, and soluble sugars during drought hardening and subsequent drought stress. It also clearly raised the activity of betaine aldehyde dehydrogenase, a key enzyme for the glycinebataine biosynhthesis as well as the activity of enzymes Δ₁-pyrroline-5-carboxylate synthetase (P5CS), glutamate dehydrogenase, arginase, and ornithine aminotransferase, all key enzymes in the proline biosynthesis. The expression of P5CS gene in the J. curcas seedlings also increased during drought hardening and subsequent drought stress, but the activity of proline dehydrogenase decreased. These results show that the drought hardening treatment can enhance drought tolerance in J. curcas, and osmoregulation is a key factor in this increased drought tolerance.

The present study investigated differences in cadmium resistance of two wheat (Triticum aestivum L.) cultivars. The cvs. RAJ 4161 (Cd resistant) and PBW 343 (Cd sensitive) were treated with 200 mg(Cd) kg^-1(soil) for 3, 5, 7, and 10 d. The effect of the Cd stress was estimated by measuring growth parameters, accumulation of cadmium, sulphur, and glutathione (GSH), and by expression of some defence genes [phytochelatin synthase (PCS), glutathione reductase (GR), and ascorbate peroxidase (APX)]. The Cd treatment resulted in a significant reduction in plant growth and in an increase in the accumulation of S and GSH. Further, the expressions of PCS, GR, and APX were also mostly enhanced. The PCS was upregulated significantly in roots of RAJ 4161 (0.6-fold) and downregulated (0.9-fold) in PBW 343 on day 3 of the Cd treatment. In RAJ 4161, the expressions of APX and GR recorded a maximum increase of 2.1- and 2.4-fold in roots and leaves, respectively, after 10 d of the stress. The results show that a different ability of RAJ 4161 and PBW 343 to modulate mRNA expression after the Cd treatment was related to their Cd tolerance.

SnRK2 are plant-specific serine/threonine kinases that are involved in plant responses to abiotic stresses. In this study, four novel genes SnRK2s:TpSnRK2.11, TpSnRK2.2, TpSnRK2.5, and TpSnRK2.10 from dwarf Polish wheat (Triticum polonicum L.) were characterized and classified into three groups. TpSnRK2.5 and TpSnRK2.11 were members of group 1; TpSnRK2.2 was member of group 2; TpSnRK2.10 belonged to group 3. The expression of TpSNRK2.2 was strongly regulated by polyethylene glycol (PEG), NaCl, and cold in roots and leaves, as well as by ABA in leaves. The transcript of TpSnRK2.5 was intensely induced by all the treatments in roots and leaves. The distinct expression patterns of TpSnRK2.10 indicate that this gene was very sensitive to ABA and NaCl, less sensitive to cold and PEG. The transcript of TpSnRK2.11 was activated significantly by PEG, NaCl, and cold, but weakly by ABA. Our results indicate that these four genes were probably involved in wheat responses to different abiotic stresses in different tissues.

Polyploidization is a major genome modification that results in plant species with multiple chromosome sets. Parental genome adjustment to co-habit a new nuclear environment results in additional innovation outcomes. We intended to assess genomic changes in polyploid model species with small genomes using inter retrotransposons amplified polymorphism (IRAP) and retrotransposon microsatellite amplified polymorphism (REMAP). Comparative analysis among diploid and autotetraploid A. thaliana and A. suecica lines with their parental lines revealed a marginal fraction of novel bands in both polyploids, and a vast loss of parental bands in allopolyploids. Sequence analysis of some remodelled bands shows that A. suecica parental band losses resulted mainly from sequence changes restricted to primer domains. Moreover, in A. suecica, both parental genomes presented rearrangement frequencies proportional to their sizes. Overall rates of genomic remodelling events detected in A. suecica were similar to those observed in species with a large genome supporting the role of retrotransposons and microsatellite sequences in the evolution of most allopolyploids.

Coleus forskohlii (syn. Plectranthus barbatus) is a widely used medicinal plant and its main bioactive constituents are diterpenes forskolin and isoforskolin. The present study aimed to construct a cDNA library to identify expressed sequence tags related to terpene biosynthesis in C. forskohlii. We constructed a high quality normalized full-length cDNA library which reached the requirements (abundance, integrity, and library content) for isolating full-length genes. A total of 4 224 cDNA clones were sequenced and 2 394 unigenes were assembled with an average unigene size of 753 bp. A total of 2 100 (87.7 %) unigenes were functionally classified using gene ontologies, and 1 716 (71.7 %) unigenes were assigned to establish pathway associations in KEGG mapings. Notably, 64 unigenes putatively participated in the biosynthesis of secondary metabolites, in which 17 unigenes were identified that might be involved in the biosynthesis of the terpenoid backbone and monoterpenes, diterpenes, and triterpenes.

To elucidate a physiological mechanism of heat stress mitigation by exogenous glucose, seedlings of Cucumis sativus cv. Jinchun No. 4 were pretreated with glucose and then exposed to normal (25/18 °C) and elevated (42/38 °C) temperatures. We investigated whether glucose can protect cucumber plantlets and chloroplast ultrastructure from heat and whether this protection is associated with antioxidant enzymes, proline, and soluble sugars. Heat inhibited plant growth, disorganized membranes of 86.33 % of chloroplasts, and elevated the content of malondialdehyde (MDA), superoxide radical (O₂ ^.-), and hydrogen peroxide (H₂O₂). An optimum concentration of glucose was 30 mM as it significantly alleviated plant growth inhibition and obviously reduced the content of MDA, O₂ ^.-, and H₂O₂ under the heat stress. The pretreatment with 30 mM glucose mitigated heat-induced damage of chloroplast ultrastructure and changes in leaf morphology more than 30 mM mannitol suggesting that glucose did not act only as osmolyte. Moreover, the glucose pretreatment increased activities of some antioxidant enzymes and enhanced the content of proline and soluble sugars under the heat stress, as well as the transcriptions of Cu/Zn-superoxide dismutase, Mn-superoxide dismutase, catalase, and glutathione reductase genes. We conclude that the pretreatment with 30 mM glucose protected chloroplast ultrastructure and enhanced heat tolerance of the seedlings by the increased activites of antioxidants and the content of proline and soluble sugars, and repressed accumulation of reactive oxygen species.

Phospholipase D (PLD) and its product phosphatidic acid are now considered to be one of the key elements of numerous physiological processes in plants including the salicylic acid signalling pathway. The presented study investigates the transcriptional regulation of Brassica napus PLDs following treatments with defense-related stimuli. We cloned eight B. napus genes encoding members of PLDβ, γ, and δ isoforms and performed phylogenetic analysis with its ancestor species Brassica rapa and Brassica oleracea, and with the model plant Arabidopsis thaliana. Transcription of the identified genes was monitored after treatment with benzothiadiazole (BTH), methyl jasmonate (MeJA), bacterial elicitor flg22, wounding, and after infection with fungal pathogens Sclerotinia sclerotiorum and Leptosphaeria maculans. Most of the genes responded specifically to a particular treatment. Remarkably the genes encoding the PLDγ and PLDβ isoforms were up-regulated by stimuli associated with the salicylic acid signalling pathway. The generality of this finding was confirmed by the analysis of public transcriptional data from Arabidopsis thaliana.

Whereas microsatellite markers are well described, there are few studies investigating minisatellites. Therefore, this study aimed to identify, characterize, and validate minisatellite loci for papaya (Carica papaya L.). The entire papaya genome, which covers 330 Mb, was used to mine minisatellites with motifs ranging from 6 to 500 bp, and at least six replicates and 82 loci were validated in a set of 24 accessions. A total of 1 730 minisatellite loci were identified, located in 695 sequences, with an average of one minisatellite every 156 kb. Variation in GC content ranged from 0.00 to 83.84 % with an average of 28.84 % indicating that these papaya minisatellites are AT rich. Motifs of up to 20 bases represented 71.45 % of the markers. In addition, the observed variation in the number of motif repeats was from 6 to 186 with an average of 9.27 per minisatellite. Independent of the classification, the frequency of minisatellites decreased with an increase in the number of repeating units. Among the validated loci, 48.78 % were found to be polymorphic, and the number of alleles (N_A) ranged from two to seven with a mean of 3.10. The average polymorphic information content (PIC), expected heterozygosity (He), and observed heterozygosity (Ho) were 0.38, 0.43, and 0.11, respectively. According to genetic diversity parameters, such as NA, He, and PIC, no significant correlations were found among the size of motifs, the number of repeats, and the GC content of these minisatellites. This study clearly demonstrates the polymorphism of minisatellites and their potential use in detection of intraspecific genetic variations in C. papaya. The results will be useful when managing genetic resources and plant breeding.

Apple (Malus × domestica Borkh.) is a perennial woody plant that undergoes a period of dormancy (in cv. Jonathan between late September and mid-December) to survive freezing temperatures of winter. DORMANCY-ASSOCIATED MADS-BOX (DAM) genes play important roles in the regulation of growth cessation and terminal bud formation in peach. To understand the role of DAM orthologs in apple, we isolated and characterized four DAM-like genes (designated as MdDAMa, MdDAMb, MdDAMc, and MdDAMd) and monitored their expression in apical buds throughout the season by real-time quantitative polymerase chain reaction analyses. The transcription of MdDAMa peaked in October and that of MdDAMc was elevated from August to October, whereas MdDAMb and MdDAMd were practically undetectable. The tandemly arranged genes MdDAMa/MdDAMb and MdDAMc/MdDAMd were localized to chromosomes 16 and 8, respectively. Based on these observations, we infer that MdDAMa and MdDAMc acted in a dominant fashion on each locus and were correlated with the period of endodormancy.

An excess of aluminum (Al) is a major factor limiting crop production in acidic soils. Secretion of organic acids (OAs) from the root apex of diverse plant species or genotypes via activation of anion channels has been recognized as the most important mechanism of Al exclusion. Citric, oxalic, and malic acids are the most effective OAs in detoxifying Al. In this review, we summarize biochemical properties of OAs secreted by plants. We also highlight the molecular mechanisms of Al signal perception, Al transport, signal regulators associated with OAs secretion, as well as interactions between Al and hormone signaling pathways. Based on a comprehensive understanding of the relationship between signal modulators and regulation of expression of relevant genes, a signal transduction model for Al-induced OAs secretion is proposed.

In order to better understand the molecular basis of heterosis in maize, the methylation-sensitive amplification polymorphism method was used to estimate patterns of cytosine methylation in seedling roots and leaves and 15-d postfertilization embryo and endosperm tissues of hybrids and their parental lines Zheng58 and Chang7-2. In all tissues, total relative methylation levels in the hybrids were lower than corresponding mid-parent values, with a higher number of demethylation events inferred for the hybrids. The trend of reduced methylation and increased demethylation in the hybrids relative to their parents may allow de-repression and possibly the expression of various genes associated with a hybrid phenotypic variation. To further investigate observed methylation pattern changes, we sequenced 50 differentially displayed DNA fragments. The BLAST analysis revealed that 13 fragments shared similarity with known functional proteins in maize or other plant species including proteins related to metabolism, transposons/retrotransposons, development, stress response, and signal transduction. The genes associated with these proteins may thus contribute significantly to maize hybrid vigour.

Little is known about Ni storage in seeds of hyperaccumulating plants and its possible role in the first stages of plant development. The aim of this study was to determine Ni distribution in seeds and seedlings during germination and to test its role during germination with and without an external Ni supply. Field-harvested seeds from the South African Ni-hyperaccumulator Berkheya coddii Roessler were germinated either in Ni-free deionised water or in ultramafic soil. Sections of seeds and seedlings were analyzed using micro-proton induced X-ray emission (micro-PIXE) in order to localise Ni and other elements. Results show that high amounts of Ni were stored within the seeds. In germinating seeds, Ni was located in different parts: the lower epidermis, margins of cotyledons, and the pericarp in the micropylar area. The Ni and Ca were not mobilised during germination sensu stricto. Emergence of the first leaf seemed to trigger the translocation of Ni and Ca within the seedling. Besides, no effect of Ni supply from soil on its redistribution could be established for the germination stage.

A protocol for plant regeneration via somatic embryogenesis was developed in two chickpea (Cicer arietinum L.) cultivars ICCV-10 and Annigeri. Somatic embryos were induced from immature cotyledons on Murashige and Skoog's (MS) medium supplemented with different concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), α-naphthaleneacetic acid (NAA) and picloram alone or in combination with 0.5 - 2.0 mg dm^-3 N⁶-benzylaminopurine (BA) or kinetin (KIN). NAA was better for somatic embryo induction compared to other auxins. The well formed, cotyledonary shaped embryos germinated into plantlets with 36.6 % frequency on MS medium supplemented with 2.0 mg dm^-3 BA + 0.5 mg dm^-3 abscisic acid (ABA). The frequency of embryogenesis and plantlet regeneration was higher in cv. ICCV-10 as compared to cv. Annigeri. Regenerated plants were transferred to soil (40 % survival) and grown to maturity. Histological studies of explants at various developmental stages of somatic embryogenesis reveled that somatic embryos developed directly from the cotyledon cells and they were single cell origin.

The interactive effects of salicylic acid (SA) and nitric oxide (NO) on alleviating cadmium (Cd) toxicity in peanut (Arachis hypogaea L.) were studied. Seedlings of two cultivars (Huayu 22 - a big seed type, and Xiaobaisha - a small seed type) were treated with 200 μM CdCl₂ without or with 0.1 mM SA or 0.25 mM sodium nitroprusside (SNP, an NO donor). Results show that the Cd exposure depressed the plant growth of both the cultivars but more of Huayu 22 than of Xiaobaisha. Exogenous SA and NO alleviated Cd toxicity in both the peanut cultivars: they improved growth, chlorophyll content, photosynthesis, and mineral nutrition. Furthermore, exogenous SA or NO decreased oxidative stress by increasing activities of antioxidant enzymes and content of non-enzymatic antioxidants. Besides, in roots and leaves of both the cultivars, exogenous SA and NO increased Cd accumulation in the cell wall and decreased Cd distribution to organelles. In particular, the effect of SA+SNP was most obvious.

Drought stress presents a considerable threat to the global crop production. As a dominant source of vegetarian diet, cereals and grain-legumes remain crucial to meeting the growing dietary demands worldwide. Therefore, breeding cultivars of these staple crops with enhanced drought tolerance stands to be one of the most sustainable solutions to enhance food production in changing climate. Given the context, a more focused survey of environment-defined germplasm sets is imperative to comprehend such adaptive traits. In parallel, uncovering the genetic architecture and the molecular networks that collectively contribute towards drought tolerance is urgently required through rationally combining large-scale genomics, proteomics, and metabolomics data. Also, attention needs to be directed to reasonably quantify the epistatic as well as environmental influences, thereby warranting deployment of analyses like metaquantitative trait loci (QTL) that encompass multiple environments and diverse genetic backgrounds. Further, innovative techniques like genomic selection (GS) and genome wide association study (GWAS) would help to capture the quantitative variation underlying drought tolerance. Equally importantly, integration of physiological traits-based techniques with ever-evolving 'omics' technologies and the new-generation phenotyping platforms will be of immense importance in advancing our existing knowledge about the genetically-complex and poorly-understood phenomena, such as plant drought response, and a deeper understanding would likely to provide a great impetus to the progress of crop breeding for drought tolerance.

The effect of benzothiadiazole (BTH) and arbutin (ARB) on sugar metabolism and plant fitness in cucumber growing hydroponically in media with different doses of NO₃ ^- and urea as nitrogen sources (100 % NO₃ ^-, 75 % NO₃ ^- + 25 % urea, and 50 % NO₃ ^- + 50 % urea) was studied on the 7^th and 14^th day after the treatment. The glucose, sucrose, and chlorophyll (Chl) content, acid and alkaline invertases and lactate dehydrogenase activities, as well as leaf area of the 3^rd and 5^th leaves were determined. Urea changed the plant sugar metabolism in a dose-, time- and leaf-age-dependent manners and influenced a cucumber response to the BTH and ARB treatments. The BTH caused a significant cessation of growth, a decrease in Chl content, a reduction of leaf area, and an enhancement of lactate dehydrogenase and alkaline invertase activities. In the older leaves of the BTH-treated plants, a high accumulation of glucose and sucrose was found. At the lower dose of urea, the metabolic changes were limited. In the ARB-treated plants, the Chl content remained unchanged in all the nitrogen variants. In these plants, decrease in glucose and sucrose content and in both invertase activities was observed mainly in younger leaves of the plants grown on the high dose of urea. The ARB improved the fitness of the cucumber plants grown in the presence of urea.

ATP binding cassette (ABC) proteins constitute one of the largest families of transporters. In Arabidopsis thaliana, over 100 genes encoding ABC transporters have been identified. Here, we described the expression pattern of AtABCC13/MRP11, a member of the multidrug resistance associated protein MRP/ABCC subfamily, previously uncharacterized. The histochemical analysis of transgenic Arabidopsis harboring AtABCC13 promoter-β-glucuronidase gene fusion shows that the AtABCC13 expression was specifically associated with vascular bundles. Moreover, AtABCC13 displayed a complex hormonal regulation. β-glucuronidase (GUS) fluorimetric assays revealed that the gene expression was induced by gibberellic acid and downregulated by naphthalene acetic acid, abscisic acid, and zeatin. Because AtABCC13 is also expressed during seed development and during germination, its expression was assessed upon exposure to various nutrients: nitrate, phosphate, and sucrose stimulated the AtABCC13 expression in seedlings, whereas their lack strongly reduced it.

An essential step in the carotenoid biosynthesis pathway is the formation of phytoene by phytoene synthase (PSY). In this study, three new genes coding PSYs (CpPSYA, CpPSYB, and CpPSYC) were cloned from Cucurbita pepo and their expression patterns analysed in three cultivars of summer squash which had a different carotenoid content. The gene sequences had a high similarity with those from other plant species, and their predicted proteins were significantly different from each other. A phylogenetic analysis indicates that CpPSYA and CpPSYB shared a high homology and were also homologous with PSYs from others cucurbits, whereas CpPSYC was more closely related to orthologues from strawberry and carrot. An expression analysis revealed that CpPSYA had a higher expression in flowers compared to leaves and showed a differential expression during fruit development. The amount of CpPSYA transcript was higher in fruits with a higher carotenoid content than in those with a lower carotenoid content. However, CpPSYB and CpPSYC showed a relatively high expression in leaves, and their expression in fruits varied among the different cultivars and fruit tissues. These results suggest that the CpPSY genes were under different regulatory mechanisms and they may have different roles in C. pepo.

Hydrogen peroxide is an effective abiotic elicitor that can induce secondary metabolite biosynthesis in plants. We show that in cell suspension culture of a salt-tolerant medicinal plant Cistanche salsa, the production of bioactive components phenylethanoid glycosides (PeGs) was increased after an H₂O₂ treatment. To identify genes related to PeGs biosynthesis affected by H₂O₂, we constructed a suppression subtractive hybridization library of H₂O₂ responsive genes using a C. salsa cell line and identified 105 expressed sequence tags (ESTs) and 85 genes. EST library functional annotation and gene ontology analyses showed genes related to various stress responses, biosynthesis of secondary metabolites, and transcriptional regulation. Among them we identified two genes related to the PeGs biosynthesis pathway (4-coumarate coenzyme A ligase and cinnamate 4-hydroxylase), and two WRKY type transcription factors. The expressions of selected genes after the H₂O₂ treatment were analyzed by RT-qPCR. An early increased transcription of PeG biosynthesis pathway genes after the treatment revealed that H₂O₂ induced PeGs biosynthesis via up-regulation of its key genes.

Pogostemon cablin (Blanco) Benth is a medicinal plant rich in terpenoids and flavonoids. Currently, the molecular mechanism of flavonoid biosynthesis in P. cablin remains unclear. In this study, three copies of the phenylalanine ammonia lyase (PAL) gene designated as PcPAL1 - PcPAL3, one copy of the chalcone synthase (CHS) gene referred to as PcCHS, and four copies of the CHS-like gene referred to as PcCHSL1 - PcCHSL4 were isolated from P. cablin. PcPAL1, PcPAL2, and PcPAL3 comprised 2 136, 2 136, and 2 148 bp full-length open reading frames (ORFs) encoding 711, 711, and 715 amino acids, respectively. PcCHS, PcCHSL1, PcCHSL2, PcCHSL3, and PcCHSL4 contained 1 173, 1 176, 1 179, 1 173, and 1 170 bp ORFs encoding 390, 391, 392, 390, and 389 amino acids, respectively. A phylogenetic analysis indicates that PcPAL2 was closer to PcPAL3 than PcPAL1, and that PcCHS was clustered with other plant CHS genes but independently to the PcCHSLs subgroup. A sequence analysis shows that PcCHSLs diverged in functional residues when compared to plant CHSs including PcCHS, suggesting that PcCHSLs may be divergent in tertiary structures. A quantitative reverse-transcription polymerase chain reaction analysis indicates that the expression profiles of PcPALs, PcCHS, and PcCHSLs in leaves and stems differed among four cultivars. Our results suggest that divergence in sequence and expression profiles of the tested genes may contribute to the diversity in flavonoids among the four cultivars.