Auxin signal transduction in plants depends on regulation by short-lived nuclear plant proteins called auxin/indole-3-acetic acid (Aux/IAA) proteins. The OsIAA9, which is highly and rapidly induced by auxin, encodes the entire Aux/IAA domain characteristic of the Aux/IAA family in rice. The promoter region of OsIAA9 contains several cis-elements. Analysis of P_OsIAA9:GUS transgenic plants indicates a specific expression of OsIAA9 in roots and seedling shoots, especially lateral roots and root tips. Based on real-time PCR, the expression of OsIAA9 was induced by multiple hormones and abiotic stresses. Furthermore, ectopic overexpression of OsIAA9 in rice led to fewer crown and lateral roots and reduced the inhibition of root elongation by auxin. These observations indicate that OsIAA9 was a negative regulator of auxin-regulated root growth.

Aims of the present two-year study were to evaluate the feasibility and identify potential drawbacks of the greenhouse/outdoors parallel plant growth methods for investigation of the effects of various winter chilling regimes on flowering quality indicators of four Greek olive cultivars, namely Mastoidis, Amfissis, and Lefkolia Serron (originating from mountainous and colder areas) compared to cv. Koroneiki (grown mainly in plain warm areas). Groups of potted olive plants were either grown outdoors under ambient temperature or transferred into a greenhouse for one, two, or three months during winter in Crete, Greece. During the first year, chilling accumulation deficit caused a marked decrease in the number of inflorescences per plant in all four olive cultivars. In the second year, chilling accumulation deficit had a negative effect on the number of inflorescences per plant in 'Mastoidis' at 3-month greenhouse treatment but not at all in 'Koroneiki'. Chilling deficit caused an overall decrease in the number of flowers per inflorescence in both 'Koroneiki' and 'Mastoidis' as well as in the percentage of morphologically perfect flowers. The width and length of inflorescences were not affected by chilling deficit in both the cultivars. In vitro pollen germination was reduced in all greenhouse treatments in 'Koroneiki'; however, this effect was significant only after 3 month, whereas no effect was observed in 'Mastoidis'. The results of the present study may contribute to understanding olive flowering biology and selecting appropriate cultivars for new plantations according to historical meteorological data and predicted climate change scenarios.

Plants are continuously exposed to unfavorable environmental conditions, such as heat stress, which negatively affect plant growth and productivity. There is evidence that phytochromes are involved in plant response to different abiotic stresses. We investigated the possible phytochrome-dependent responses to heat stress in photomorphogenic tomato mutants aurea (au, phytochromobilin-deficient, PΦB) and high-pigment 1 (hp1, hyperresponsive to phytochrome-mediated responses), as well as the wild-type Micro-Tom (MT). In comparison with MT, reductions in photosynthetic rate promoted by a high temperature were more pronounced in au, whereas less pronounced in hp1. All genotypes subjected to the heat stress exhibited adjustments in the capture and dissipation of energy, which were indicated by increases in the initial fluorescence and decreases in the maximum photochemical efficiency of photosystem II (PS II). The effective quantum yield of PS II and the apparent electron transport rate showed greatest alterations in the au mutant. In addition, heat-triggered anatomical changes occurred in all genotypes but were most conspicuous in the au mutant, followed by MT. Thus, phytochrome-dependent mechanisms played pivotal roles in the plant responses to the heat stress, and deficiency in phytochromobilin biosynthesis enhanced the heat-induced impairment of photosynthetic performance.

Calmodulin-binding transcription activators (CAMTAs) play important roles in plant growth, developmental processes, and responses to abiotic and biotic factors. Recently, five CAMTA members were identified in Citrus sinensis, however, very little is known about the molecular regulation of these CAMTAs in citrus during fruit development and under abiotic stresses. In this study, the different expression profiles of CsCAMTA genes were found in different tissues and different fruit developmental stages. The CsCAMTA genes also displayed distinct expression patterns after heat, cold, salt, and drought stresses. Furthermore, the expressions of CsCAMTA genes were significantly induced by treatments with salicylic acid, methyl jasmonate, or abscisic acid. The green fluorescent protein gene fused with CsCAMTA was specifically expressed in the nucleus of Nicotiana benthamiana cells. Additionally, CsCAMTA proteins can activate or suppress DNA transcription in yeast. These findings provide helpful information for further studies of stress signals in citrus.

Superoxide dismutase is a crucial reactive oxygen species (ROS) scavenger and converts the superoxide radical (O₂^-) to H₂O₂, so it is thought to enhance abiotic stress tolerance by reducing ROS accumulation and so avoiding oxidative damage. In this study, we isolated a salt- and oxidative stress-responsive Cu/Zn SOD gene TaSOD5 from wheat. The ectopic overexpression of TaSOD5 in Arabidopsis increased total and Cu/Zn SOD activities, and offered the plant tolerance to salt stress. Arabidopsis ectopically expressing TaSOD5 possessed a superior resistance to oxidative stress induced H₂O₂. The TaSOD5 ectopic overexpression elevated the activities of both ROS scavengers and O₂^- producer NADPH oxidase. These findings show that Cu/Zn SOD enhances salt tolerance via regulating the machinery of redox homeostasis rather than improving SOD activity alone.

A unique structural feature of plant sterols is the presence of a 24-alkyl group in the sterol side chain, which is synthesized by C24-sterol methyltransferase (SMT). Here we report for the first time that the bread wheat genome (AABBDD) contains at least three homoeologous genes encoding C24-sterol methyltransferase 1. While these copies have similar coding regions, they differ markedly in the nucleotide sequences of their non-coding regions. Sequencing de novo of the promoter regions of the TaSMT1 homoeologs demonstrated the occurrence of common and specific stress-sensitive cis-elements such as LTR, the cis-element involved in low temperature response. These cis-elements, along with other factors, determine the differences in the effects of stress on the expression of homoeologous TaSMT1 genes. For example, TaSMT1-5A is constitutively expressed in the roots and leaves, while TaSMT1-4D gene is highly stress-responsive. Another important enzyme involved in sterol biosynthesis is C22-sterol desaturase, which converts β-sitosterol into stigmasterol. This enzyme is encoded by homoeologous TaCYP710A8 genes, which, in contrast to TaSMT1, are all up-regulated in response to stress. Cold-induced expression of TaCYP710A8 is greater in roots than in leaves. This may be due to the higher cold sensitivity of the roots and the necessity to increase the amount of stigmasterol known as a “stress sterol”. Our findings suggest that the existence of homoeologous genes of sterol biosynthesis in polyploid plants supports the diversity of genetic mechanisms of sterol-mediated response of plants to stresses.

Tea plant (Camellia sinensis) is a typical plant that accumulates abundant aluminum (Al) and fluoride (F). Al and F play vital roles in the growth and development in tea plant. MYB (myeloblastosis) is one of the largest transcription factor families in plant, which plays an important role in the stress responses. As the largest and multifunctional subfamily of MYB, R2R3-MYB subfamily participates in multiple abiotic stresses in plant. However, there are few studies about R2R3-MYB in tea plant, especially in the accumulation of Al and F during its growth. Here, we identified 43 CsMYB genes from the transcriptome database of tea plant and analyzed the relative expression in Al and F treatments. According to the Arabidopsis thaliana classification, 43 CsMYB genes are divided into 18 subgroups via phylogenetic tree analysis. All 43 CsMYB proteins have the typical R2R3-MYB domain by MEME prediction. Moreover, 9 CsMYB genes (CsMYB11, CsMYB17, CsMYB29, CsMYB38 to CsMYB43) that related to abiotic stress were selected from 43 CsMYB genes for a further study, and the relative expressions showed that they are tissue-specifically expressed. In addition, the results of different concentrations of Al treatments showed that CsMYB11, -17, -29, -38 and -41 are stimulated by Al treatment. The results of different concentrations of F treatments showed that the CsMYB11, -17, -38, -39, -40, -41, -42 and -43 participate in F accumulation of C. sinensis roots. Our research establishes a solid foundation for further investigation into the molecular functions of R2R3-MYB transcription factors in C. sinensis.

Zeaxanthin epoxidase (ZEP) plays important roles in plant growth and development due to its functions in abscisic acid (ABA) biosynthesis and in the xanthophyll cycle. Many studies have been exploring the roles of ZEP in seed germination and response to various environmental stresses. In this study, we reported that heterologously overexpressing the ZEP gene from Medicago sativa (MsZEP) in tobacco increased ABA content in tobacco mature seeds and negatively regulated seed germination. Enhanced ABA synthesis in seed embryo and delayed germination might also be related to the increased 9-cis-epoxycarotenoid dioxygenase (NCED6) expression. Moreover, we found that overexpression of MsZEP resulted in an increased expression of the SOMNUS gene but a decreased expression of the DNA ligase 6 gene (Lig6) suggesting that MsZEP might affect seed proteome and DNA integrity. Furthermore, enhanced chlorophyll content in transgenic tobacco seedlings overexpressing MsZEP might be due to its function in the xanthophyll cycle and ABA biosynthesis.

A leading figure in the field of plant physiology
RNDr. Bohdan Slavík, DrSc.
passed away on 1^st August 2018 at the age of 93.

Salt stress is one of the most critical environmental factors limiting plant growth, and hydrogen sulfide (H2S) can play a role in plant responses to this stress. To investigate the effects of H2S on mitochondrial functions under salt stress, we treated Malus hupehensis Rehd. var. pingyiensis germinating seeds with an 85 mM NaCl solution with or without an H2S donor sodium hydrosulfide (NaHS) and H2S scavenger hypotaurine (HT). Then, hydrogen peroxide (H2O2) content and antioxidant enzyme activities were measured in mitochondria of seedling roots. Our results show that the application of 0.05 mM NaHS rescued an NaCl-induced inhibition of root elongation, decreased H2O2 content, and enhanced superoxide dismutase (SOD), guaiacol peroxidase (POD), and catalase (CAT) activities in the mitochondria compared to NaCl treatment alone. It was also found that 0.05 mM NaHS significantly decreased the mitochondrial permeability transition pore and increased mitochondrial membrane fluidity, mitochondrial membrane potential, and cytochrome c/a ratio under NaCl stress. However, 0.02 mM NaHS did not affect root growth, antioxidant enzyme activities, and mitochondrial function under NaCl stress, whereas high concentrations of NaHS (more than 0.2 mM) had a weaker or negative effects. Moreover, 15 µM HT eliminated the beneficial effects of NaHS under NaCl stress. Our results suggest that H2S protected plants against salt stress by decreasing H2O2 accumulation and by regulating membrane stability and antioxidant system in mitochondria.

Salinity adversely affects plants resulting in disruption to plant growth and physiology. Previously, it has been shown that these negative effects can be alleviated by various exogenous polyamines. However, the role of spermidine (Spd) in conferring salinity tolerance in sorghum is not well documented. The effect of exogenous Spd on the responses of sweet sorghum (Sorghum bicolor L.) seedlings to salt stress (150 mM NaCl) was investigated by measuring photosynthetic carbon assimilation, Calvin cycle enzyme activities, and the the expression of respective genes. Application of 0.25 mM Spd alleviated the negative effects of salt stress on efficiency of photosystem II and CO₂ assimilation and increased the activities of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) and aldolase. Salt stress significantly lowered the transcriptions of genes encoding Rubisco large subunit, Rubisco small subunit, 3-phosphoglyceric acid kinase, glyceraldehyde-3-phosphate dehydrogenase, triose-3-phosphate isomerase, fructose-1,6-bisphosphate aldolase, fructose-1,6-bisphosphate phosphatase, and sedoheptulose-1,7-bisphosphatase. However, transcriptions of genes encoding phosphoribokinase and Rubisco were up-regulated. The Spd application enhanced expressions of most of these genes. It appears Spd conferred salinity tolerance to sweet sorghum seedlings by enhancing photosynthetic efficiency through regulation of gene expressions and activities of key CO₂ assimilation enzymes.

Plant flotillins, a subgroup of the SPFH domain protein superfamily, consist of three proteins, AtFLOT1, AtFLOT2, and AtFLOT3 in Arabidopsis thaliana. The exact functions of flotillins in plant cell has not been established yet. In this study we focused on the role of flotillins in response to both abiotic and biotic stresses and on the response to phytohormones abscisic acid and 1-naphthalene acetic acid (NAA) in A. thaliana. We observed transcriptomic changes of AtFLOT genes in response to high salinity and cold, treatment with 22-amino acid peptide from N-terminal part of flagellin (flg22), and after infection with Botrytis cinerea. Transcription of AtFLOT2 increased up to 60 times after flg22 treatment. Also, treatment with B. cinerea increased transcription of AtFLOT1 10 times and of AtFLOT3 14 times. Furthermore, we used T-DNA knock-out single mutants for all three A. thaliana flotillins and we measured root growth in response to high salinity, cold, phosphate starvation, nitrogen starvation, and abscisic acid and NAA treatments. Subsequently, we measured the reactive oxygen species production and callose accumulation after the treatment with flg22. Next, we performed resistance assays to Pseudomonas syringae pv. tomato DC3000 and B. cinerea. In contrast to transcriptomic changes, knocking-out of only single FLOT gene did not lead to significant changes in response to all tested stresses.

Gibberellic acid (GA) is a natural plant growth regulator (PGR) which stimulates germination, vegetative growth, flowering, and fruit formation. However, when high concentrations of GA are used, it inhibits plant growth and development and causes abnormalities in the plant tissue. In our study, we determined the effects of different concentrations of GA on Allium cepa L. var. cepa roots. Increasing concentrations of GA (50 - 5 000 mg dm^-3) were used in A. cepa root growth inhibition tests. Further, random amplified polymorphic DNA technique was used for determination of possible genotoxic effects of 600 - 1200 mg dm^-3 GA on A. cepa root tips. Our findings show cytotoxic and genotoxic effects of these concentrations of GA and indicate that the difference among control and treatment groups were statistically significant.

The roles of ethylene responsive factors (ERFs) and their positive and negative regulations of abiotic stress tolerance have been widely reported. This study reports the characterization of ItERF from Iris typhifolia Kitag with respect to molecular and functional properties. The 867 bp cDNA fragment of ItERF was cloned by reverse transcription PCR from I. typhifolia. Real-time quantitative PCR revealed that ItERF expression was induced in the roots, stems, and leaves of I. typhifolia after NaCl treatment, and that ItERF expressions were significantly higher in the leaves and roots than in the stems. A green fluorescent protein marker revealed that ItERF was located to the nucleus. Plant survival and root growth of ItERF transgenic Arabidopsis thaliana L. seedlings were much better than those of the wild type under NaCl stress. Malondialdehyde content in the transgenic lines was significantly lower than that in the wild type. Growth of yeast transformants showed an enhanced tolerance to salt stress than non-transformed yeast cells. All of the results verified that the expression of ItERF had effects on plant growth under salt stress.

Tissue/organ-specific promoters are important tools in genetic engineering and crop molecular breeding. They are well characterized in dicots, such as Arabidopsis, tobacco, and tomato, but not sufficiently in monocots, especially in wheat. In this study, the genes specifically expressed in seven different tissues, including coleoptile, root, leaf, pistil, anther, embryo, and endosperm were identified through analyzing the public transcriptome data from a wheat microarray using the ROKU method. The expression patterns of selected genes were validated by reverse transcription polymerase chain reaction. The results showed that these selected genes were expressed specifically or preferentially in each representative tissue/organ. Moreover, the function of their promoters was verified by transient expression in wheat or stable transformation in Arabidopsis. The results showed that these promoters can efficiently and predominantly drive uidA (β-glucuronidase) reporter gene expression in different tissues. Due to their tissue-specific nature, these promoters can be used as potential candidates in plant genetic engineering.

Plant hormones play important roles in seed dormancy and dormancy breaking. We measured the hormone content in rice (Oryza sativa L. cv. Nona Bokra) seeds at different stages and with or without imbibition treatment. We identified 1 265 differentially expressed genes (DEGs) between dormant and dormancy-broken seeds using RNA-seq analysis: 1 015 genes were significantly up-regulated, while 250 genes were significantly down-regulated. Sixteen DEGs were selected as related to seed dormancy, and their expressions were validated using quantitative PCR. Three DEGs were in the same position as two reported dormancy QTLs, suggesting that they may be candidate genes that control the dormancy of rice seeds. Our study provides an important basis for cloning genes in dormant rice seeds and provides theoretical support for the study of the dormancy mechanism.

Potato (Solanum tuberosum L.), a plant of great economic importance worldwide, is known to be highly sensitive to salinity. Improving the tolerance of this crop was envisaged using interspecific somatic hybridization. In this report, the impact of salinity on three hybrid lines (STBa, STBc, and STBd) produced by protoplast fusion between the cv. BF15 and the wild species Solanum berthaultii was investigated in vitro. An analysis of plant response to oxidative stress was considered when plantlets were submitted to 100 mM NaCl for 5 d. The peroxidation of membrane lipids was screened by measuring malondialdehyde accumulation in these lines. Moreover, gene expressions and activities of antioxidant enzymes, such as catalase (CAT), peroxidase (POX), and superoxide dismutase (SOD), were assessed. The results show a lower degree of lipid peroxidation in the hybrid lines in comparison to the BF15 parent. These hybrids also showed higher activities of CAT, POX, and SOD than the BF15, especially in roots. The significant inductions of FeSOD, (Cu-Zn)SOD, MnSOD, and CAT genes in hybrid plants suggest their participation in salt tolerance. The differential expressions of the SOD and CAT genes between leaves and roots also indicate their tissue specificity.

The ATP binding cassette B/multidrug-resistance/P-glycoprotein (ABCB/MDR/PGP) subfamily is a member of the ABC protein family. Significant progress has been made in the functional characterization of ABCB genes, particularly in Arabidopsis thaliana. This review evaluates recent advances concerning the plant ABCB subfamilies including their evolution and structure, the involvement and regulation of ABCB-mediated auxin transport, and the roles of ABCBs in plant growth and development. Insights into specific functions of members of the ABCB subfamily and their mediation of various regulatory pathways are also presented.

The vesicle trafficking process, which involves exocytotic and endocytotic pathways, has been reported to play a role in regulating plant responses to different environmental stresses. The Exo70 protein is important for the localization of the exocyst in the plasma membrane; however, its role in the physiology of stress tolerance is currently unclear. In this study, we characterized NbExo70D1, an Exo70 gene from tobacco (Nicotiana benthamiana). It was shown to have a role in the plant response to salt stress. More specifically, tolerance to salt stress is conferred by the overexpression of the dominant negative nbexo70d1 domain D mutation in transgenic tobacco. In addition, a reduced accumulation of reactive oxygen species (ROS) under salt treatment was observed in the transgenic lines compared to the wild type. Treatment with diphenylene iodonium, an NADPH oxidase inhibitor, resulted in a decrease in salt stress-triggered ROS production in the roots of both wild type tobacco and transgenic tobacco. Furthermore, there was a reduction in NADPH oxidase activity in the transgenic plants under salt treatment, which indicates NbExo70D1 is involved in NADPH oxidase-mediated ROS production. We also characterized the tissue-specific expression patterns of NbExo70D1 during salt stress response by expressing the ProNbExo70D1-β-glucuronidase reporter construct in plants. Importantly, the GFP-NbExo70D1 fusion protein was localized in both the plasma membrane and the cytoplasm; expressing the dominant negative mutation disrupted the interaction between NbExo70D1 protein and the plasma membrane. Overall, our study suggests that Exo70 plays an important role in regulating the production and transmission of ROS as part of a salt stress response in plants.

Sucrose, proline, and polyamines are compatible solutes accumulating in plant tissues and increasing cellular osmolarity under environmental stresses. These compatible solutes and hydrogen peroxide can function as signaling molecules in plants. There has been very little evidence how the supply of sucrose changes the biosynthesis of compatible solutes. This study aimed to assess the cross-talk among sucrose, H₂O₂, and compatible solutes on the expression of genes encoding key enzymes in the pathways of proline and polyamine metabolism in drought stressed maize seedlings. Drought stress (induced by polyethylene glycol solution) increased the expressions of genes encoding pyrroline-5-carboxylate synthetase (P5CS), arginine decarboxylase (ADC), and S-adenosylmethionine decarboxylase (SAMDC), while decreased proline dehydrogenase (ProDH), diamine oxidase (DAO), and polyamine oxidase (PAO) expressions. Addition of sucrose to the stressed seedlings increased the P5CS, ADC and SAMDC expressions more than drought stress alone and reduced more the ProDH, DAO, and PAO expressions. Moreover, exogenous sucrose increased leaf water potential and the content of proline, polyamines, and total soluble sugars, whereas decreased H₂O₂ content and membrane damages under the drought stress conditions. Consequently, exogenous sucrose contributed to the preservation of water status and the amelioration of damage in maize seedlings under the drought stress.

Virus-induced gene silencing (VIGS) is a particularly useful tool for functional genomics. In the present study, we attempted to utilize this technology to infer the function of genes from Viola philippica using a tobacco rattle virus (TRV) construct. Firstly, the phytoene desaturase gene from V. philippica (VpPDS) was silenced, and local leaf bleaching was observed but did not exhibit systemic effects, thereby limiting utilization of TRV-mediated gene silencing in the recipient plant. However, we observed systemic gene silencing in Nicotiana benthamiana when the VpPDS sequence was used as a trigger, thereby suggesting that heterologous gene sequences could elicit gene silencing. We then investigated the role of gene PISTILLATA from V. philippica (VpPI) of the B-class MADS-box gene family, which regulates the identity and development of stamens and petals. Using the coding region of VpPI as triggers, we determined the gene silencing efficiency of the corresponding GLOBOSA paralogs in N. benthamiana (NbGLO1 and NbGLO2), and we observed stamen-to-carpel transformation and distorted corollas in N. benthamiana suggesting that VpPI functioned as the NbGLO gene. However, the 3'-untranslated region (3'UTR) of VpPI and each 3'UTR of the NbGLO genes downregulated its own corresponding gene, hardly producing floral homeotic alterations. This work provides a better understanding of gene-specific probe design for gene silencing as well as shows that heterologous sequence-triggered VIGS is an efficient way to investigate functional conservation of orthologous genes.

Salsola laricifolia, a typical C₃-C₄ intermediate desert plant, is an important for understanding gene evolution and mechanisms for drought resistance. The reverse transcription quantitative polymerase chain reaction (RT-qPCR) is a preferred choice for gene expression studies, but it requires stable reference genes for normalization. Therefore, we tested the expression stability of five candidate reference genes in S. laricifolia: EF1α (elongation factor 1-α), ACT (actin), GAPDH (glyceraldehyde-3-phosphate dehydrogenase), TUB (tubulin), and 18S (18S ribosomal RNA). The expressions were tested in different tissues and under five stresses caused by abscisic acid (ABA), NaCl, NaHCO₃, darkness, and osmotic stress (polyethylene glycol 6000, PEG). Four commonly used software programs (geNorm, NormFinder, BestKeeper, and RefFinder) were used. The results show the following most stable reference genes: GAPDH for ABA and dark treatments; EF1a for NaCl, PEG; and all samples; TUB for NaHCO₃; and 18S for the controls. The ACT was not ranked first in any group, and was the least stable reference gene under the dark, NaHCO₃, and PEG. Moreover, pairwise analysis by the geNorm algorithm shows that two best reference genes were 18S and EF1a for the controls, GAPDH, and 18S for the ABA and dark treatments, EF1a and TUB for the NaCl treatment, TUB and 18S for the NaHCO₃ treatment, EF1a and GAPDH for the PEG treatment, and EF1a and 18S for all samples. The reference genes for RT-qPCR in S. laricifolia identified in our study will facilitate future work on targeted gene expression.

The "Specific Tissue" (ST) are proteins of unknown function present only in some plant families, mainly Fabaceae and Asteraceae. They are included in the PF10950 protein family and characterized by the presence of at least one domain of unknown function (DUF)2775. In this work we studied the involvement of the six members of the Medicago truncatula ST family (ST1 to ST6) in the development of flowers, fruits, and seeds by analysing the activity of their promoters (pST) after the construction of M. truncatula transgenic plants expressing the b-glucuronidase (GUS) reporter gene under the control of the six pSTs. The GUS activity was analysed in whole flowers and fruits and also in histological sections of these organs. The pST expression in the reproductive organs was mainly associated with the vascular bundles, especially throughout fruit development. These results pointed to an important role of ST proteins during the reproductive development stage, related to nutrient mobilization during the fruit and seed formation, that could be facilitated by their presence in the pod vascular bundles, as well as in the connective tissue of the anthers (ST3, ST4, ST6), in the placenta, the funiculus, and the outer parts of the developing seed (ST2, ST3, ST6). The observations made in this study were in agreement with the functions previously established for the three groups of M. truncatula ST proteins, as in the proposed function for ST1 in the transport and assimilation of nutrients, or the involvement of ST4, ST5, and ST6 in floral defence.

Interactions between indole-3-acetic acid (IAA), abscisic acid (ABA), and ethylene (ET) in the photoperiodic flower induction of a short-day (SD) plant Pharbitis nil were investigated. It was shown that both IAA and ABA applied just before and during the first half of the 16-h-long inductive night inhibited flower induction in P. nil. Ethylene is also thought to be a strong flowering inhibitor of SD plants but only when it is applied in the second half of the inductive night. The application of IAA just before the inductive night decreased the content of endogenous ABA in cotyledons only during the first half of the inductive night. Additionally, the application of 2-aminoethoxyvinylglycine (AVG) - an ethylene biosynthesis inhibitor - partially reversed the inhibitory effect of IAA and ABA on flowering. The results suggest that the mechanisms of P. nil flower inhibition by IAA and ABA might be independent. However, both the hormones influenced ethylene production which directly inhibited flowering. We also show that ABA applied on the cotyledons of P. nil seedlings just before the inductive night caused a clear increase in the expression of PnACS1 and PnACS2 genes (encoding enzymes involved in ethylene biosynthesis) from the first hours after its application. The transcripts of PnACO1 and PnACO3 genes were also increased but their maximal values were shifted in relation to the PnACS1 and PnACS2. The data presented here strongly support the idea that both IAA and ABA inhibit P. nil flowering through the modulation of ethylene biosynthesis.

Plant glutathione peroxidases (GPX) catalyze the reduction of H₂O₂ or organic hydroperoxides to water, mitigating the toxicity of these compounds to cells. In rice plants, the GPX gene family is composed of five members that are distributed in a range of sub-cellular compartments including cytosol, mitochondria, chloroplasts, or endoplasmic reticulum. Of these, OsGPX1 and OsGPX4 are located in mitochondria and chloroplasts, respectively. To understand the role of these GPX in rice, the effect of knockdown of OsGPX1 and OsGPX4 in rice plants was evaluated. Our data show that OsGPX4 was essential for in vitro rice regeneration because no plants were obtained from calli carrying a hairpin construct against OsGPX4. Although the knockdown of OsGPX1 did not impair plant regeneration, the plants with silenced OsGPX1 (GPX1s plants) showed reduced shoot length and a reduced number of seeds compared to the non-transformed rice plants. These results indicate that OsGPX1 and OsGPX4 are essential for redox homeostasis which leads to normal growth and development of rice.

Innate immune system is employed by plants to defend against phytopathogenic microbes through specific perception of non-self molecules and subsequent initiation of resistance responses. Current researches elucidate that plants mostly rely on cell surface-located pattern recognition receptors (PRRs) and intracellular nucleotide-binding leucine-rich repeat proteins (NB-LRRs) to recognize pathogen-associated molecular patterns (PAMPs) and effector proteins from microbial pathogens, initiating PAMP- and effector-triggered immunity (PTI and ETI), respectively. Some pathogenic bacterial effector proteins are usually secreted into plant cells and play a virulence function by suppressing plant PTI, implying an evolutionary process of plant immunity from PTI to ETI. In the past several years, a great progress has been achieved to reveal fascinating molecular mechanisms underlying the pathogenic recognition, resistance signaling transduction, and plant immunity evolution. Here, we summarized the latest breakthroughs about these topics, and offered an integral understanding of plant molecular immunity.

Phalaenopsis species are among the most popular potted flowers for their fascinating flowers. When their whole-genome sequencing was completed, they have become useful for studying the molecular mechanism of anthocyanin biosynthesis. Here, we identified 49 candidate anthocyanin synthetic genes in the Phalaenopsis genome. Our results showed that duplication events might contribute to the expansion of some gene families, such as the genes encoding chalcone synthase (PeCHS), flavonoid 3'-hydroxylase (PeF3'H), and myeloblastosis (PeMYB). To elucidate their functions in anthocyanin biosynthesis, we conducted a global expression analysis. We found that anthocyanin synthesis occurred during the very early flower development stage and that the flavanone 3-hydroxylase (F3H), F3'H, and dihydroflavonol 4-reductase (DFR) genes played key roles in this process. Over-expression of Phalaenopsis flavonoid 3',5'-hydroxylase (F3'5'H) in petunia showed that it had no function in anthocyanin production. Furthermore, global analysis of sequences and expression patterns show that the regulatory genes are relatively conserved and might be important in regulating anthocyanin synthesis through different combined expression patterns. To determine the functions of MYB2, 11, and 12, we over-expressed them in petunia and performed yeast two-hybrid analysis with anthocyanin (AN)1 and AN11. The MYB2 protein had strong activity in regulating anthocyanin biosynthesis and induced significant pigment accumulation in transgenic plant petals, whereas MYB11 and MYB12 had lower activities. Our work provided important improvement in the understanding of anthocyanin biosynthesis and established a foundation for floral colour breeding in Phalaenopsis through genetic engineering.

This review reports the physiological and metabolic changes in plants during development under elevated atmospheric carbon dioxide concentration and/or limited-nitrogen supply in order to establish their effects on leaf senescence induction. Elevated CO₂ concentration and nitrogen supply modify gene expression, protein content and composition, various aspects of photosynthesis, sugar metabolism, nitrogen metabolism, and redox state in plants. Elevated CO₂ usually causes sugar accumulation and decreased nitrogen content in plant leaves, leading to imbalanced C/N ratio in mature leaves, which is one of the main factors behind premature senescence in leaves. Elevated CO₂ and low nitrogen decrease activities of some antioxidant enzymes and thus increase H₂O₂ production. These changes lead to oxidative stress that results in the degradation of photosynthetic pigments and eventually induce senescence. However, this accelerated leaf senescence under conditions of elevated CO₂ and limited nitrogen can mobilize nutrients to growing organs and thus ensure their functionality.

Previous studies on microwave exposure on plants have revealed variations in sensitivity of plants to different microwave frequencies, exposure durations, and power intensities. However, the effects of different polarizations of microwaves on plants have not been studied. Therefore, we investigated the effect of horizontally and vertically polarized 2 GHz continuous microwaves on Myriophyllum aquaticum plants at 1.8 W m^-2 power density. The electric potential variation along the vascular tissues were investigated for 1.5 h and growth parameters, pigmentation, and H₂O₂ formation were studied during 48 h microwave exposure. Exposure to horizontally polarized microwaves, decreased standard deviation of electric potential variation and increased H₂O₂ content significantly. Vertically polarized microwaves increased the standard deviation of electric potential variation and photosynthetic pigments significantly. However, none of the polarizations altered growth parameters (shoot length, stem diameter, and internodal length). Thermographic images taken for 1 h continuous microwave exposure did not indicate alteration in the temperature of the plants for both vertical and horizontal polarities.

Elucidation of mechanisms underlying plant tolerance to cadmium, a widespread toxic soil pollutant, and accumulation of Cd in plants are urgent tasks. For this purposes, the pea (Pisum sativum L.) mutant SGECd^t (obtained by treatment of the laboratory pea line SGE with ethylmethane sulfonate) was reciprocally grafted with the parental line SGE, and four scion/rootstock combinations were obtained: SGE/SGE, SGECd^t/SGECd^t, SGE/SGECd^t, and SGECd^t/SGE. They were grown in hydroponics in the presence of 1 μM CdCl₂ for 30 d. The SGE and SGECd^t scions on the SGECd^t rootstock had a higher root and shoot biomass and an elevated root and shoot Cd content compared with the grafts having SGE rootstock. Only the grafts with the SGE rootstock showed chlorosis and roots demonstrating symptoms of Cd toxicity. The content of nutrient elements in roots (Fe, K, Mg, Mn, Na, P, and Zn) was higher in the grafts having the SGECd^t rootstock, and three elements, namely Ca, Fe, and Mn, were efficiently transported by the SGECd^t root to the shoot of these grafts. The content of other measured elements (K, Mg, Na, P, and Zn) was similar in the root and shoot in all the grafts. Then, the non-grafted plants were grown in the presence of Cd and subjected to deficit or excess concentrations of Ca, Fe, or Mn. Exclusion of these elements from the nutrient solution retained or increased differences between SGE and SGECd^t in growth response to Cd toxicity, whereas excess of Ca, Fe, or Mn decreased or eliminated such differences. The obtained results assign a principal role of roots to realizing the increased Cd-tolerance and Cdaccumulation in the SGECd^t mutant. Efficient translocation of Ca, Fe, and Mn from roots to shoots appeared to counteract Cd toxicity, although Cd was actively taken up by roots and accumulated in shoots.