JA Treatment Research Articles

Improved pokeweed genome assembly and early gene expression changes in response to jasmonic acid

BackgroundJasmonic acid (JA) is a phytohormone involved in regulating responses to biotic and abiotic stress. Although the JA pathway is well characterized in model plants such as Arabidopsis thaliana, less is known about many non-model plants. Phytolacca americana (pokeweed) is native to eastern North Americana and is resilient to environmental stress. The goal of this study was to produce a publicly available pokeweed genome assembly and annotations and use this resource to determine how early response to JA changes gene expression, with particular focus on genes involved in defense.ResultsWe assembled the pokeweed genome de novo from approximately 30 Gb of PacBio Hifi long reads and achieved an NG50 of ~ 13.2 Mb and a minimum 93.9% complete BUSCO score for gene annotations. With this reference, we investigated the early changes in pokeweed gene expression following JA treatment. Approximately 5,100 genes were differentially expressed during the 0–6 h time course with almost equal number of genes with increased and decreased transcript levels. Cluster and gene ontology analyses indicated the downregulation of genes associated with photosynthesis and upregulation of genes involved in hormone signaling and defense. We identified orthologues of key transcription factors and constructed the first JA gene response network integrated with our transcriptomic data from orthologues of Arabidopsis genes. We discovered that pokeweed did not use leaf senescence as a means of reallocating resources during stress; rather, most secondary metabolite synthesis genes were constitutively expressed, suggesting that pokeweed directs its resources for survival over the long term. In addition, pokeweed synthesizes several RNA N-glycosylases hypothesized to function in defense, each with unique expression profiles in response to JA.ConclusionsOur investigation of the early response of pokeweed to JA illustrates patterns of gene expression involved in defence and stress tolerance. Pokeweed provides insight into the defense mechanisms of plants beyond those observed in research models and crops, and further study may yield novel approaches to improving the resilience of plants to environmental changes. Our assembled pokeweed genome is the first within the taxonomic family Phytolaccaceae to be publicly available for continued research.

Jasmonic acid priming and foliar application of spermidine up-regulates the tolerance mechanisms to alleviate the damaging effects of cadmium stress on growth and photosynthesis in wheat

The study examined the effects of jasmonic acid (100 nmol, JA) priming and foliar application of spermidine (1 mM, Spd), both individually and combined, on mitigating cadmium (100 µM, Cd) stress-induced oxidative damage in wheat. Cadmium stress reduced plant height and dry mass, but JA priming and/or Spd treatment increased resistance. Cd stress significantly decreased carotenoids, total chlorophylls, glutamate 1-semialdehyde (GSA), and δ-aminolevulinic acid (ALA), but JA and Spd treatments counteracted these reductions. Photosynthetic parameters improved under JA and Spd treatments, with combined treatment showing greater alleviation. Cd exposure increased lipid peroxidation, hydrogen peroxide, electrolyte leakage, and superoxide, but these oxidative stress indicators were significantly reduced after JA and Spd treatment. Antioxidant enzyme activity was upregulated by JA priming and Spd application, both under unstressed and Cd-stressed conditions. JA and/or Spd treatments also increased ascorbic acid, lowered glutathione concentration, and upregulated glyoxylase activity, reducing methylglyoxal accumulation. Additionally, secondary compounds (phenols and flavonoids) and osmolytes (proline and glycine betaine) levels improved. Proline oxidase activity decreased, indicating controlled proline buildup, while γ-glutamyl kinase activity increased. JA and/or Spd treatments significantly reduced Cd accumulation in seedlings. The study concluded that JA and Spd treatments enhance the plant's defensive mechanisms against oxidative stress by boosting antioxidant enzymes and secondary metabolism.

Supplementation of Jasmonic acid Mitigates the Damaging Effects of Arsenic Stress on Growth, Photosynthesis and Nitrogen Metabolism in Rice

Experiments were conducted to evaluate the role of exogenously applied jasmonic acid (JA; 0.1 and 0.5 µM) in alleviating the toxic effects of arsenic (As; 5 and 10 µM) stress in rice. Plants treated with As showed considerable decline in growth attributes like height, fresh and dry weight of plant. Arsenic stress reduced the content of δ-amino livulenic acid (δ-ALA), glutamate 1-semialdehyde (GSA), total chlorophylls and carotenoids, with more reduction evident at higher (10 µM) As concentrations, however exogenously supplied JA alleviated the decline to considerable extent. Arsenic stress mediated decline in photosynthetic gas exchange parameters, Fv/Fm (PSII activity) and Rubisco activity was alleviated by the exogenous treatment of JA. Arsenic stress caused oxidative damage which was evident as increased lipid peroxidation, lipoxygenase activity and hydrogen peroxide concentrations however, JA treatment declined these parameters. Treatment of JA improved the activity of nitrate reductase and glutamate synthase under unstressed conditions and also alleviated the decline triggered by As stress. Activity of antioxidant enzymes assayed increased due to As stress, and the supplementation of JA caused further increase in their activities. Moreover, the content of proline, free amino acids and total phenols increased significantly due to JA application under stressed and unstressed conditions. Treatment of JA increased the content of nitrogen and potassium while as reduced As accumulation significantly.

SbMYC2 mediates jasmonic acid signaling to improve drought tolerance via directly activating SbGR1 in sorghum.

SbMYC2 functions as a key regulator under JA signaling in enhancing drought tolerance of sorghum through direct activating SbGR1. Drought stress is one of the major threats to crop yield. In response to drought stress, functions of basic helix-loop-helix (bHLH) transcription factors (TFs) have been reported in Arabidopsis and rice, but little is known for sorghum. Here, we characterized the function of SbMYC2, a bHLH TF in sorghum, and found that SbMYC2 responded most significantly to PEG-simulated drought stress and JA treatments. Overexpression of SbMYC2 significantly enhanced drought tolerance in Arabidopsis, rice and sorghum. In addition, it reduced reactive oxygen species (ROS) accumulation and increased chlorophyll content in sorghum leaves. While silencing SbMYC2 by virus-induced gene silencing (VIGS) resulted in compromised drought tolerance of sorghum seedlings. Moreover, SbMYC2 can directly activate the expression of GLUTATHIONE-DISULFIDE REDUCTASE gene SbGR1. SbGR1 silencing led to significantly weakened drought tolerance of sorghum, and higher ROS accumulation and lower chlorophyll content in sorghum leaves were detected. In addition, SbMYC2 can interact with SbJAZs, suppressors of JA signaling, and thus can mediate JA signaling to activate SbGR1, thereby regulating sorghum's tolerance to drought stress. Overall, our findings demonstrate that bHLH TF SbMYC2 plays an important role in sorghum's response to drought stress, thus providing one theoretical basis for genetic enhancement of sorghum and even rice.

Cloning and expression pattern analysis of abscisic acid receptor gene McPYL4 in Mentha canadensis

Mentha canadensis is a traditional Chinese herb with great medicinal and economic value. Abscisic acid(ABA) receptor PYLs have important roles in plant growth and development and response to adversity. The M. canadensis McPYL4 gene was cloned, and its protein characteristics, gene expression, and protein interactions were analyzed, so as to provide genetic resources for genetic improvement and molecular design breeding for M. canadensis resistance. Therefore, the protein characteristics, subcellular localization, gene expression pattern, and protein interactions of McPYL4 were analyzed by bioinformatics analysis, transient expression of tobacco leaves, RT-qPCR, and yeast two-hybrid(Y2H) techniques. The results showed that the McPYL4 gene was 621 bp in length, encoding 206 amino acids, and its protein had the conserved structural domain of SRPBCC and was highly homologous with Salvia miltiorrhiza SmPYL4. McPYL4 protein was localized to the cell membrane and nucleus. The McPYL4 gene was expressed in all tissue of M. canadensis, with the highest expression in roots, followed by leaves, and it showed a pattern of up-regulation followed by down-regulation in leaves 1-8. In both leaves and roots, the McPYL4 gene responded to the exogenous hormones ABA, MeJA, and the treatments of drought, AlCl_3, NaCl, CdCl_2, and CuCl_2. Moreover, McPYL4 was up-regulated for expression in both leaves and roots under the MeJA treatment, as well as in leaves treated with AlCl_3 stress for 1 h, whereas McPYL4 showed a tendency to be down-regulated in both leaves and roots under other treatments. Protein interactions showed that McPYL4 interacted with AtABI proteins in an ABA-independent manner. This study demonstrated that McPYL4 responded to ABA, JA, and several abiotic stress treatments, and McPYL4 was involved in ABA signaling in M. canadensis and thus in the regulation of leaf development and various abiotic stresses in M. canadensis.

AaGL3-like is jasmonate-induced bHLH transcription factor that positively regulates trichome density in Artemisia annua

The leaves of Artemisia annua contain GSTs (Glandular secretory trichomes) that can secrete and store artemisinin, the drug most effective for treating uncomplicated malaria. Therefore, increasing the density of GSTs in A. annua is an efficient way to enhance artemisinin content. However, our understanding of how GSTs develop still needs to be improved. Here, we isolated an A. annua homolog of AtGL3 (GLABRA3), known as AaGL3-like, that positively regulates trichome density in A. annua. AaGL3-like is nuclear-localized and transcriptionally active. It is least expressed in roots and most prominently in aerial components like leaves, stems, and inflorescence. Under JA and GA hormonal treatments, AaGL3-like expression is significantly increased. In transgenic over-expression AaGL3-like lines, trichome developmental genes such as AaHD1 and AaGSW2 showed much increased expression. The AaGL3RNAi line exhibited considerably lower levels of AaHD1 and AaGSW2 transcripts. As a result, the AaGL3-RNAi lines showed reduced levels of artemisinin content and trichome density compared to wild-type and overexpression lines. Additionally, we have found that when co-expressed with AaJAZ8, the induction of trichome developmental genes was reduced as compared to individual OEAaGL3-like lines. Further, AaJAZ8 directly binds to AaGL3-like in the Y2H assay. These findings suggest that AaGL3-like is a jasmonate-induced bHLH transcription factor that drastically increases the final accumulation of artemisinin content by regulating trichome density in A. annua.

Genome-wide identification of DUF506 gene family in Oryzasativa and expression profiling under abiotic stresses.

The domain of unknown function 560 (DUF560), also known as the PDDEXK_6 family, is a ubiquitous plant protein that has been confirmed to play critical roles in Arabidopsis root development as well as ABA and abiotic responses. However, genome-wide identification and expression pattern analysis in rice (Oryza sativa) still need to be improved. Based on the phylogenetic relationship, 10 OsDUF506 genes were identified and classified into four subfamilies. Segmental duplication was essential to the expansion of OsDUF506s, which were subjected to purifying selective pressure. Except for OsDUF50609 and OsDUF50610, the OsDUF506s shared colinear gene pairs with five monocot species, showing that they were conserved in evolution. Furthermore, the conserved domains, gene structures, SNPs distribution, and targeting miRNAs were systematically investigated. Massive cis-regulatory elements were discovered in promoter regions, implying that OsDUF506s may be important in hormone regulation and abiotic stress response. Therefore, we analyzed plant hormone-induced transcriptome data and performed qRT-PCR on eight OsDUF506s under drought, cold, and phosphorus-deficient stresses. The results revealed that most OsDUF506s respond to ABA and JA treatment, as well as drought and cold conditions. In conclusion, our findings provided insights into the evolution and function of OsDUF506s, which could benefit crop breeding in the future.

Identification of Reliable Reference Genes under Different Stresses and in Different Tissues of Toxicodendron succedaneum.

Toxicodendron succedaneum (L.) Kuntze (T. succedaneum) is an economic tree species that produces urushiol and urushi wax, and it is of great value in industry and medicine. However, the stability of reference genes (RGs) has not been systematically reported in T. succedaneum to date. In this study, the expression of 10 candidate RGs was analyzed by RT-qPCR in different tissues (roots, stems, leaves), stress treatments (high/low temperature, drought), and hormone stimulation (jasmonic acid, JA). Then, the stability ranking of 10 candidate genes was evaluated by ∆Ct analysis and three software programs: geNorm, NormFinder, and BestKeeper. Finally, RefFinder was used to comprehensively analyze the expression stability of 10 candidate genes. The comprehensive analysis showed that TsRG05/06, TsRG01/06, and TsRG03/ACT were stable under high/low-temperature stress, drought stress, and JA treatment, respectively. TsRG03 and ACT had stable expression in different tissues. While the TsRG03 and ACT were recommended as the suitable RGs for T. succedaneum in all samples. Meanwhile, UBQ was the least suitable as a reference gene for T. succedaneum. In addition, the results of geNorm showed that the combination of two stable RGs could make the results of gene expression more accurate. These results provide alternative RGs for the study of gene function, correction, and normalization of target gene expression and directed molecular breeding in T. succedaneum.

Overexpression of TaMYC2 confers freeze tolerance by ICE-CBF-COR module in Arabidopsis thaliana.

Dongnongdongmai No.1 (Dn1) is one of the few winter wheat varieties that can successfully overwinter at temperatures as low as -25°C or even lower. To date, few researches were carried to identify the freeze tolerance genes in Dn1 and applied them to improve plant resistance to extreme low temperatures. The basic helix-loop-helix (bHLH) transcription factor MYC2 is a master regulator in JA signaling, which has been reported to involve in responses to mild cold stress (2°C and 7°C). We hypothesized that MYC2 might be part of the regulatory network responsible for the tolerance of Dn1 to extreme freezing temperatures. In this study, we showed that wheat MYC2 (TaMYC2) was induced under both extreme low temperature (-10°C and-25°C) and JA treatments. The ICE-CBF-COR transcriptional cascade, an evolutionary conserved cold resistance pathway downstream of MYC2, was also activated in extreme low temperatures. We further showed that overexpression of any of the MYC2 genes from Dn1 TaMYC2A, B, D in Arabidopsis led to enhanced freeze tolerance. The TaMYC2 overexpression lines had less electrolyte leakage and lower malondialdehyde (MDA) content, and an increase in proline content, an increases antioxidant defences, and the enhanced expression of ICE-CBF-COR module under the freezing temperature. We further verified that TaMYC2 might function through physical interaction with TaICE41 and TaJAZ7, and that TaJAZ7 physically interacts with TaICE41. These results elucidate the molecular mechanism by which TaMYC2 regulates cold tolerance and lay the foundation for future studies to improve cold tolerance in plants.

Reference genes selection of Paeonia ostii 'Fengdan' under osmotic stresses and hormone treatments by RT-qPCR.

Tree peony possess significant ornamental, medicinal and oil values. Osmotic stresses including dehydratiuon and salinity limit the expansion of cultivation area of tree peony. Information on reference genes selection under osmotic stress and hormone stimulation of tree peony still limited. This study aimed to determine the stable reference genes suitable for tree peony under osmotic stresses and hormone treatments, and provide a theoretical basis for the molecular biology research. Twelve candidate reference genes were evaluated in Paeonia ostii 'Fengdan' under osmotic stress and hormone treatments by RT-qPCR. Delta Ct method, geNorm, and NormFinder were used for the comprehensive expression stability ranking comparison. The results revealed that tubulin-α was the preferred internal reference genes for drought and ABA treatment, tubulin-β was identified as the most suitable reference gene under drought and OPDA induction, 18s-rRNA was regarded as the most stable gene for salinity and JA treatment, eIF-5A was listed as the most stable gene for JA and MeJA treatments. The experiments also displayed that EF1-α were comparatively unstable under ABA and BR hormone treatments. These preferred reference genes could be useful in qPCR studies involving osmotic or hormonal stresses in Paeonia ostii 'Fengdan'. It is anticipated that the results will benefit tree peony functional genomics studies and molecular breeding research in the future.

Physiological and protein profiling analysis provides insight into the underlying molecular mechanism of potato tuber development regulated by jasmonic acid in vitro

BackgroundJasmonates (JAs) are one of important phytohormones regulating potato tuber development. It is a complex process and the underlying molecular mechanism regulating tuber development by JAs is still limited. This study attempted to illuminate it through the potential proteomic dynamics information about tuber development in vitro regulated by exogenous JA.ResultsA combined analysis of physiological and iTRAQ (isobaric tags for relative and absolute quantification)-based proteomic approach was performed in tuber development in vitro under exogenous JA treatments (0, 0.5, 5 and 50 μΜ). Physiological results indicated that low JA concentration (especially 5 μM) promoted tuber development, whereas higher JA concentration (50 μM) showed inhibition effect. A total of 257 differentially expressed proteins (DEPs) were identified by iTRAQ, which provided a comprehensive overview on the functional protein profile changes of tuber development regulated by JA. The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis indicated that low JA concentration (especially 5 μM) exhibited the promotion effects on tuber development in various cellular processes. Some cell wall polysaccharide synthesis and cytoskeleton formation-related proteins were up-regulated by JA to promote tuber cell expansion. Some primary carbon metabolism-related enzymes were up-regulated by JA to provide sufficient metabolism intermediates and energy for tuber development. And, a large number of protein biosynthesis, degradation and assembly-related were up-regulated by JA to promote tuber protein biosynthesis and maintain strict protein quality control during tuber development.ConclusionsThis study is the first to integrate physiological and proteomic data to provide useful information about the JA-signaling response mechanism of potato tuber development in vitro. The results revealed that the levels of a number of proteins involved in various cellular processes were regulated by JA during tuber development. The proposed hypothetical model would explain the interaction of these DEPs that associated with tuber development in vitro regulated by JA.

Jasmonic acid-induced resistance to fall armyworm in soybeans: Variation among genotypes and tradeoffs with constitutive resistance

A negative correlation between constitutive and inducible resistance across plant populations is expected for a variety of reasons; however, empirical evidence for such trade-offs remain ambiguous, particularly for crop plants. The current study investigated the relationship between constitutive and inducible resistance in vegetative-stage soybeans (V5-V6) against larvae of the generalist defoliator, Spodoptera frugiperda. Eighteen soybean genotypes differing in their constitutive resistance to coleopteran or lepidopteran defoliators were used over four experiments. Exogenous jasmonic acid (JA, 2 mM) was used to induce plants. Constitutive resistance of each genotype was estimated by measuring weight gains, foliar consumption, and foliar conversion efficiency in short-term feeding assays on excised leaf disks of terminal trifoliate leaves of plants not treated with JA. JA was applied to plants immediately after removing leaf material for assays of constitutive resistance, and induced resistance was estimated 48 h after application of JA using leaf disks from the remaining leaf tissue of the same trifoliate used for measuring constitutive resistance. Larval weight gains before JA treatments revealed genotypic variability in constitutive resistance. . Overall, reductions in weight gain (28.7% to 76.7%), foliar consumption (3.7% - 65%) and conversion efficiency (10.9% - 42.2%) were found in JA treatments. Significant (P < 0.05) or marginally significant (P < 0.10) negative correlations between constitutive resistance (larval weight gains on non-induced plants) and induced resistance (differences in weight gains before and after induction) were found in all four experiments, suggesting tradeoff between the two modes of resistance does exist in soybean for this herbivore. Additional evidence for tradeoffs between constitutive and inducible resitance was also found in the analysis of consumption data. Comparisons of consumption and conversion efficiencies suggest that similar antibiotic and antixenotic factors are involved in constitutive and inducible resistance to fall armyworm in soybean.

AaMYB15, an R2R3-MYB TF in Artemisia annua, acts as a negative regulator of artemisinin biosynthesis

Artemisinin is a secondary metabolite extracted from Artemisia annua. As an effective antimalarial component certified by WHO, artemisinin has extensive economical values. Numerous studies about transcription factors positively regulating artemisinin biosynthesis have been published while negative regulators are rarely reported. In the present study, we identified AaMYB15 as the first R2R3-MYB that negatively regulates artemisinin biosynthesis in A. annua. Experimental evidences showed that AaMYB15 is a transcription factor within nucleus and predominantly expressed in glandular secretory trichomes (GSTs) in A. annua where artemisinin is synthesized and accumulated. The expression of AaMYB15 was induced by dark and JA treatment. Overexpression of AaMYB15 led to a significant decline in the expression levels of key enzyme genes ADS, CYP, DBR2, and ALDH1 and a significant decrease in the artemisinin contents of transgenic A. annua. AaMYB15 directly bound to the promoter of AaORA, a reported positive regulator of artemisinin biosynthesis in JA signaling pathway, to repress its transcriptional activity, thus downregulating the expression levels of downstream key enzyme genes and negatively regulating the artemisinin biosynthesis. Our study provides candidate gene for improvement of A. annua germplasm and new insights into the artemisinin biosynthesis regulation network mediated by light and JA.

An updated census of the maize TIFY family.

The TIFY gene family is a plant-specific gene family encoding a group of proteins characterized by its namesake, the conservative TIFY domain and members can be organized into four subfamilies: ZML, TIFY, PPD and JAZ (Jasmonate ZIM-domain protein) by presence of additional conserved domains. The TIFY gene family is intensively explored in several model and agriculturally important crop species and here, yet the composition of the TIFY family of maize has remained unresolved. This study increases the number of maize TIFY family members known by 40%, bringing the total to 47 including 38 JAZ, 5 TIFY, and 4 ZML genes. The majority of the newly identified genes were belonging to the JAZ subfamily, six of which had aberrant TIFY domains, suggesting loss JAZ-JAZ or JAZ-NINJA interactions. Six JAZ genes were found to have truncated Jas domain or an altered degron motif, suggesting resistance to classical JAZ degradation. In addition, seven membranes were found to have an LxLxL-type EAR motif which allows them to recruit TPL/TPP co-repressors directly without association to NINJA. Expression analysis revealed that ZmJAZ14 was specifically expressed in the seeds and ZmJAZ19 and 22 in the anthers, while the majority of other ZmJAZs were generally highly expressed across diverse tissue types. Additionally, ZmJAZ genes were highly responsive to wounding and JA treatment. This study provides a comprehensive update of the maize TIFY/JAZ gene family paving the way for functional, physiological, and ecological analysis.

Genome-wide identification and characterization of DEAD-box helicase family associated with early somatic embryogenesis in Dimocarpus longan Lour

DEAD-box (DDX) proteins belong to the largest subfamily of RNA helicase SF2, which contributes to all biological processes of RNA metabolism in the plant kingdom. Till now, no significant data are available regarding studies on DDX in Somatic Embryogenesis (SE) of woody plants. It is important to investigate the biological function of the DlDDX family in longan SE. Thus, a comprehensive analysis of 58 longan DEAD-box (DlDDX) genes characterization was performed by genome-wide identification and transcript abundance validation analysis. Homologous evolution has revealed that some DlDDXs in longan had high sequence similarity with Mus musculus, Citrus and Saccharomyces cerevisiae, indicating that DlDDXs were highly conservative in the animal, plant, and microorganism. Remarkably, gene duplication, purifying selection, and alternative splicing events, and new auxiliary domains have likely contributed to the functional evolution of DlDDX, indicating that DlDDX appeared neofunctionalization in longan. Besides, DlDDX3, 15, 28, 36 might interact with protein complex (MAC3A, MAC3B, CDC5, CBP20) of miRNA biosynthesis. Notably, DlDDX28 contained a novel auxiliary domain (CAF-1 p150), which might contribute to DNA demethylation in longan early SE. 4 DlDDX genes significantly expressed not only in early SE and zygotic embryogenesis (ZE) but also up-regulated at high levels in ‘Honghezi’ and ‘Quanlongbaihe’ with abortive seeds, which are of great significance. Moreover, some DlDDXs presented abiotic stress-response dynamic expression patterns by ABA, SA, JA, and NaCl treatments during early SE. Hence, DEAD-box is essential to SE development and seed abortive in longan.

Genome-wide identification, structure analysis and expression profiling of phospholipases D under hormone and abiotic stress treatment in chickpea (Cicer arietinum)

Phospholipases D (PLDs) are phospholipid hydrolyzing enzymes and crucial components of lipid signaling in plants. PLDs are implicated in stress responses in different plants however, characterization of PLDs in chickpea is missing. Here, we identify 13 PLD genes in the chickpea genome. PLD family could be divided into α, β, δ, ε and ζ isoforms based on sequence and structure. Protein remodeling described that chickpea PLDs are composed of defined arrangements of α-helix, β-sheets and short loops. Phylogenetic analysis suggested evolutionary conservation of chickpea PLD family with dicots. In-planta subcellular localization showed the plasma membrane localization of chickpea PLDs. All PLD promoters had hormone and stress related cis-regulatory elements, which suggested overlapping function of PLDs in hormone and abiotic stress signaling. The qRT-PCR expression analysis revealed that most PLD genes are differentially expressed in multiple abiotic stresses (drought, salt and cold stress). Moreover, several PLD genes had overlapping expression in abiotic stress and ABA and JA treatment. These observations indicate the involvement of PLD gene family in cross-talk of phytohormone and abiotic stress signaling in chickpea. Thus, present study opens new avenues of utilizing PLD related information for understanding hormone-regulated abiotic stress signaling in legume crops.

Physiological and molecular comparative analysis of two contrasting rice varieties under jasmonic acid treatment

Rice is one of the most important crops but its productivity is severely threatened by both biotic and abiotic stresses. Jasmonic acid and its derivatives (referred to JA) are the lipid-based plant hormones that were commonly known as regulators of plant growth, development and defense responses. In this study, we compare the physiological and molecular responses of two rice accessions, G38 (Nep_nuong) and G11 (Tam-tron) to JA treatment. G38 plants under JA treatment experienced a reduction in shoot length, root weight, shoot weight and total plant weight which suggested its sensitiveness to JA, whereas G11 plants showed a less reduction in these traits. The expression levels of 12 JA-related genes were investigated in order to better understand how the JA biosynthesis and responses differ in these two contrasting rice accessions. A significantly higher expression level of a set of genes related to JA biosynthesis, signaling and response in G11 compare to G38 was observed. Furthermore, the inorganic phosphorus starvation (Pi) response was also examined in the two varieties G11 and G38. In low Pi condition (40 µM), G11 plants showed more roots, longer root length and shoot length, higher weight compared to the G38 plants which suggest that G11 did not suffer much effect of Pi deficiency. This study highlights the differences in JA growth response in 2 contrasting rice genotypes and also suggests the link between JA developmental response and the tolerance to the Pi starvation condition in rice.

Genome-wide identification and expression analysis of SABATH methyltransferases in tea plant (Camellia sinensis): insights into their roles in plant defense responses

ABSTRACT SABATH methyltransferases convent plant small-molecule metabolites into volatile methyl esters, which play important roles in many biological processes and defense reactions in plants. In this study, a total of 32 SABATH genes were identified in the Camellia sinensis var. sinensis (CSS) genome, which were renamed CsSABATH1 to CsSABATH32. Genome location annotation suggested that tandem duplication was responsible for the expansion of SABATH genes in tea plant. Multiple sequence alignment and phylogenetic analysis showed that the CsSABATHs could be classified into three groups (I, II and III), which were also supported by gene structures and conserved motifs analysis. Group II contained only two CsSABATH proteins, which were closely related to PtIAMT, AtIAMT and OsIAMT. The group III SABATH genes of tea plant exhibited expansion on the CSS genome compared with Camellia sinensis var. assamica (CSA) genome. Based on RNA-seq data, the CsSABATHs exhibited tissue-specific expression patterns, and the members with high expression in buds and young leaves were also obviously upregulated after MeJA treatment. The expression of many transcription factors was significantly correlated with that of different members of the CsSABATH gene family, suggesting a potential regulatory relationship between them. Quantitative real-time PCR (qPCR) expression analysis showed that CsSABATHs could respond to exogenous JA, SA and MeSA treatments in tea plants. RNA-seq data analysis and qPCR validation suggested that CsSABATH8, 11, 16, 25, 29 and 32 might play a special role in plant defense against insect herbivory. These results provide references for evolutionary studies of the plant SABATH family and the exploration of the potential roles of CsSABATHs in tea plant defense responses.

Response of BpBZR genes to abiotic stress and hormone treatment in Betula platyphylla

Brassinazole-resistant (BZR) transcription factors have important roles in the brassinosteroid (BR) signalling pathway and are widely involved in plant growth and abiotic stress processes. However, there are few studies on the functions and regulatory mechanisms of BZR TFs in birch. In this study, 5 BZR genes were identified from birch. The qRT-PCR results showed that the expression levels of most BpBZRs were significantly downregulated and/or upregulated in at least one organ following NaCl and PEG stress or ABA, GA3 and JA treatments. In particular, BpBZR1 expression was changed in all three organs after exposure to NaCl stress at all time points, indicating that this gene may be involved in salt stress. The BpBZR1 transcription factor was shown to have transcriptional activation activity in a yeast two-hybrid assay. Through a transient transformation system, we found that overexpression of BpBZR1 in birch resulted in lower H2O2 and MDA accumulation, higher SOD and POD activities and maintained a higher photosynthetic intensity and a lower chlorophyll degradation rate than those of the control plants under salt stress. These results preliminarily showed that overexpression of the BpBZR1 gene increased the tolerance of birch to salt stress.

Jasmonic and Abscisic Acid Contribute to Metabolism Re-adjustment in Strawberry Leaves under NaCl Stress

ABSTRACT The aim of this research was to evaluate the effect of exogenous jasmonic acid and abscisic acid, at different salinity regimes, on primary and secondary metabolic changes in ʻKurdistanʼ and ʻQueen Elisaʼ strawberry leaves. To this end, strawberry plants were induced by gradual NaCl salinity (10 mmol•L−1) and shock salinity. The plants were sprayed with ABA (40 mmol•L−1) and JA treatments up to 40 mmol•L−1. In both cultivars, salt shock stress significantly enhanced the total antioxidant capacity, though the JA treatment outperformed the ABA treatment. Increasing JA level in the presence of ABA resulted in downswing in total phenolic content (6.42% in ʻKurdistanʼ and 23.13% in ʻQueen Elisaʼ) and antioxidant capacity (12.9% in ʻKurdistanʼ and 17.7% in ʻQueen Elisaʼ) at non-saline conditions. Adding both hormonesresulted in a 20.82% increase in total phenolic content and a 17.86% increase in total antioxidant capacity in ‘Kurdistan’ at gradual salt stress; however, in ʻQueen Elisaʼ, the same treatment resulted in 21.98% increase in total phenol and 11.92% increase in total antioxidant capacity at salt shock. Salt shock induced tyrosine increase and both hormones enhanced asparagine, alanine, histidine, and GABA contents in ʻQueen Elisaʼ. The study reveals that the applation of abscisic acid along with different jasmonic acid concentrations activates the protective mechanism of the strawberry plant against NaCl stress. Further studies are needed to compare the exact salt stress tolerance mechanisms for these cultivars. Abbreviations: JA: Jasmonic acid; ABA: Abscisic Acid; GABA: γ-Aminobutyric acid