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.

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Drought causes detrimental effect on growth and productivity of many plants, including crops. Chickpea (Cicer arietinum L.) as one of the most important legume crops is subjected to terminal drought stress in arid and semi-arid regions. Transcription factors (TFs) play key roles during signal transduction and adaptation response to abiotic stresses such as drought. In the present study, TFs were assessed in a transcriptome analysis in the root and the shoot tissues of two contrasting drought responsive kabuli chickpea. Out of 4572 differentially expressed genes, 1806 TFs were identified using search on the plant transcription factor database (PTFD). The highest members (101) of the TFs belonged to bHLH family, followed by ERF (87), kinase superfamily (76), NAC (74), MYB (72), WRKY (72), etc. The comparison of the tolerant (Bivanij) and the sensitive (Hashem) cultivars under drought stress showed that the TFs were differently distributed based on the cultivars and the tissue types. The TF families including B3, NAC, MYB, WRKY, bHLH, etc. had most members in response to the drought stress. Furthermore, the results revealed that several TFs which were involved in abiotic stress-related responses and major biosynthetic pathways such as ABA and proline biosynthesis were upregulated in the shoot of Bivanij as compared to Hashem indicating the vital role of the shoot for inducing drought tolerance in the tolerant cultivar. As result, these findings help the researches to better understanding of signal transduction and stress-related regulating networks in chickpea and provide the transferring of key TFs and promoting drought tolerance by genetic engineering.

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