Application of gamma rays on salinity tolerance of wheat (Triticum aestivum L.) and expression of genes related to biosynthesis of proline, glycine betaine and antioxidant enzymes

We investigated the effects of salinity stress and gamma radiation on salinity tolerance in wheat crops. To this end, mutant lines were generated by exposing Arg and Bam wheat varieties at the primordial state to 150 and 200 gamma radiation doses in the field. The top 15 mutant lines were specified for cultivation in the fifth-generation under two conditions, including non-stress and salinity stress. According to Fernandez's model, the three mutant lines had high yields under both conditions. The three mutant lines were selected with their two parents, and then, cultivated in a completely randomized factorial design in a greenhouse under non-stress and salinity conditions. The mutant lines showed significantly higher osmotic adjustment, leaf relative water content (RWC), potassium ion concentration, soluble sugar content and lower proline (Pro), and glycine betaine (GB) content than the parents at both the vegetative (VEG) and reproductive (REP) stages under salinity conditions. The expression of genes involved in the Pro biosynthesis pathway, P5CS and P5CR genes, in mutant lines were less than their parents, and conversely, P5CDH in mutant lines was more than their parents. The changes in the expression of CMO and BADH genes involved in the GB synthesis pathway indicated that the mutant lines had less gene expression compared to their parent genotypes of Arg and Bam. The results indicated an increase in antioxidant activity in the mutant lines compared to their parents. Consequently, irradiated plants have probably adapted to the salinity stress by increasing the osmotic adjustment, RWC, potassium ion concentration, and soluble sugar content, as well as activating antioxidant enzymes.

RNA-Seq analysis revealed genes associated with drought stress response in kabuli chickpea (Cicer arietinum L.)

Drought is the most important constraint that effects chickpea production globally. RNA-Seq has great potential to dissect the molecular mechanisms of tolerance to environmental stresses. Transcriptome profiles in roots and shoots of two contrasting Iranian kabuli chickpea genotypes (Bivanij and Hashem) were investigated under water-limited conditions at early flowering stage using RNA-Seq approach. A total of 4,572 differentially expressed genes (DEGs) were identified. Of these, 261 and 169 drought stress responsive genes were identified in the shoots and the roots, respectively, and 17 genes were common in the shoots and the roots. Gene Ontology (GO) analysis revealed several sub-categories related to the stress, including response to stress, defense response and response to stimulus in the tolerant genotype Bivanij as compared to the sensitive genotype Hashem under drought stress. In addition, several Transcription factors (TFs) were identified in major metabolic pathways such as, ABA, proline and flavonoid biosynthesis. Furthermore, a number of the DEGs were observed in "QTL-hotspot" regions which were reported earlier in chickpea. Drought tolerance dissection in the genotypes revealed that the genes and the pathways involved in shoots of Bivanij were the most important factor to make a difference between the genotypes for drought tolerance. The identified TFs in the experiment, particularly those which were up-regulated in shoots of Bivanij during drought stress, were potential candidates for enhancing tolerance to drought.