Drought tolerance mechanisms in chickpea (Cicer arietinum L.) investigated by physiological and transcriptomic analysis

Chickpea is a grain legume that enhances soil fertility and represents an important source of green proteins forhuman health. It is typically cultivated in marginal areas with limited water availability. The aim of this studywas to shed light into the molecular mechanisms of drought tolerance of this legume. First, the physiologicalresponse of nine stable genotype lines in control and drought-stress conditions was assessed. Two of these genotypes(Desi PI5980808 and Kabuli Flip07 318 C) showed opposite physiological responses to drought stress.Desi PI5980808 displayed a reduced chlorophyll content and an unaltered concentration of osmolytes (prolineand soluble sugars) under drought stress. Kabuli Flip07 318 C did not show any reduction in photosynthesis andchlorophyll content, but a significant increase of proline and soluble sugars was observed under the droughtstress. To identify genes and molecular mechanisms involved in drought tolerance, RNA-seq was performed incontrol conditions and after one week of drought stress in these two contrasting genotypes. The genotype withhigher drought sensitivity showed more intense changes in gene expression than the genotype with less sensitivity,up-regulating genes involved in photophosphorylation process (transferases, oxygen lyases and oxidoreductases),hormones (brassinosteroids, abscisic acid and gibberellin response), solute transporters, nutrientuptake, and cell wall properties (cellulose synthases, hemicellulose synthases, poligalacturonases, pectate lyases).Small number of up-regulated genes in the genotype with lower drought sensitivity included thoseinvolved in chromatin modifications. These results will be helpful for further studies aiming at identifying genesand molecular markers to be used in breeding strategies to develop chickpea cultivars more resilient to waterstress.