Identification of genes associated to ß -N oxalyl- L-α, ß-diaminopropionic acid and their role in mitigating salt stress in a low-neurotoxin cultivar of Lathyrus sativus.

Grass pea has the potential to become a miracle crop if the stigma attached to it as a toxic plant is ignored. In light of the following, we conducted transcriptome analyses on the high and low ODAP-containing cultivars i.e., Nirmal and Bidhan respectively in both normal and salt stress conditions. In this study, genes that work upstream and downstream to ß-ODAP have been found. Among these genes, AAO3 and ACL5 were related to ABA and polyamine biosynthesis, showing the relevance of ABA and polyamines in boosting the ß-ODAP content in Nirmal. Elevated ß-ODAP levels in salt stress-treated Bidhan may have evolved tolerance by positively regulating the expression of genes involved in phenylpropanoid and jasmonic acid biosynthesis. Although the concentration of ß-ODAP in Bidhan increased under salt stress, it was lower than in stress-treated Nirmal. Despite this, the expression of stress-related genes that work downstream to ß-ODAP was found higher in stress-treated Bidhan. This could be because stress-treated Nirmal has lower GSH, proline, and higher H2O2, resulting in the development of severe oxidative stress. Overall, our research not only identified new genes linked with ß-ODAP, but also revealed the molecular mechanism by which a low ß-ODAP-containing cultivar developed tolerance against salinity stress.

Glutathione imparts stress tolerance against Alternaria brassicicola infection via miRNA mediated gene regulation.

Glutathione (GSH) is well known to play a crucial role in imparting resistance against various pathogen invasions. Nevertheless, the role of GSH in regulating miRNA-mediated defense response is yet to be explored. To decipher the GSH-mediated regulation of miRNA expression during necrotrophic infection in Arabidopsis thaliana, wild-type Col-0 and AtECS1, the transgenic line exhibiting enhanced GSH content, were infected with necrotrophic pathogen Alternaria brassicicola. AtECS1 plants exhibited enhanced resistance as compared to wild-type. MiRNA next-generation sequencing (NGS) was performed to compare the miRNA expression in Col-0 and AtECS1 leaves. Under control condition, differentially expressed 96 known miRNAs and 17 novel miRNAs viz. ath-miR8167f, ath-miR1886.3, ath-miR3932b-5p, etc. were identified. However, under infected condition, 73 known and 43 novel differentially expressed miRNAs viz. ath-miR5652, ath-miR160b, ath-miR865-5p, etc. were identified. Functional annotation and enrichment analysis revealed that several miRNAs that target defense-related genes like leucine-rich repeat protein kinase, MYB transcription factors, TCP8, etc. were down regulated in the AtECS1 line, which, in turn, relieves the repression of their target gene expression, leading to resistance against infection. Together, the present investigation suggests that GSH plays a decisive role in modulating the miRNA-mediated regulation of defense-related genes during pathogen invasion.

Comparative Genome Analysis Across 128 Phytophthora Isolates Reveal Species-Specific Microsatellite Distribution and Localized Evolution of Compartmentalized Genomes.

Phytophthora sp. are invasive groups of pathogens belonging to class Oomycetes. In order to contain and control them, a deep knowledge of their biology and infection strategy is imperative. With the availability of large-scale sequencing data, it has been possible to look directly into their genetic material and understand the strategies adopted by them for becoming successful pathogens. Here, we have studied the genomes of 128 Phytophthora species available publicly with reasonable quality. Our analysis reveals that the simple sequence repeats (SSRs) of all Phytophthora sp. follow distinct isolate specific patterns. We further show that TG/CA dinucleotide repeats are far more abundant in Phytophthora sp. than other classes of repeats. In case of tri- and tetranucleotide SSRs also, TG/CA-containing motifs always dominate over others. The GC content of the SSRs are stable without much variation across the isolates of Phytophthora. Telomeric repeats of Phytophthora follow a pattern of (TTTAGGG)n or (TTAGGGT)n rather than the canonical (TTAGGG)n. RxLR (arginine-any amino acid-leucine-arginine) motifs containing effectors diverge rapidly in Phytophthora and do not show any core common group. The RxLR effectors of some Phytophthora isolates have a tendency to form clusters with RxLRs from other species than within the same species. An analysis of the flanking intergenic distance clearly indicates a two-speed genome organization for all the Phytophthora isolates. Apart from effectors and the transposons, a large number of other virulence genes such as carbohydrate-active enzymes (CAZymes), transcriptional regulators, signal transduction genes, ATP-binding cassette transporters (ABC), and ubiquitins are also present in the repeat-rich compartments. This indicates a rapid co-evolution of this powerful arsenal for successful pathogenicity. Whole genome duplication studies indicate that the pattern followed is more specific to a geographic location. To conclude, the large-scale genomic studies of Phytophthora have thrown light on their adaptive evolution, which is largely guided by the localized host-mediated selection pressure.

Interplay between glutathione and mitogen-activated protein kinase 3 via transcription factor WRKY40 under combined osmotic and cold stress in Arabidopsis.

Glutathione (GSH) plays a fundamental role in plant defense. Recent reports showed that enhanced GSH content activates mitogen-activated protein kinases (MPKs). However, the molecular mechanism behind this GSH-mediated MPKs expression during environmental challenges is unexplored. Here, we found that under control and combined abiotic stress-treated conditions, GSH feeding activates MPK3 expression in Arabidopsis thaliana by inducing its promoter, as established through the promoter activation assay. Additionally, transgenic A. thaliana overexpressing the LeMPK3 gene (AtMPK3 line) showed increased γ-ECS expression, which was decreased in mpk3, the MPK3-depleted mutant. An in-gel kinase assay exhibited hyperphosphorylation of Myelin Basic Protein (MBP) in the GSH-fed AtMPK3 transgenic line. Under control and combined abiotic stress treated conditions, expression of transcription factor WRKY40 binding to MPK3 promoter was up-regulated under enhanced GSH condition. Interestingly, GSH feeding was rendered ineffective in altering MPK3 expression in the Atwrky40 mutant, emphasizing the involvement of WRKY40 in GSH-MPK3 interplay. This was further confirmed by a wrky40 co-transformation assay. The immunoprecipitation assay followed by ChIP-qPCR showed a significant increase in the binding of WRKY40 to MPK3 promoter, which further established MPK3-WRKY40 association upon GSH feeding. In conclusion, this study demonstrated that GSH modulates MPK3 expression via WRKY40 in response to stress.