Transcript profiling and gene expression analysis under drought stress in Ziziphus nummularia (Burm.f.) Wright & Arn.

Abstract

Drought is one of the prime abiotic stresses responsible for limiting agricultural productivity. A number of drought responsive genes have been isolated and functionally characterized but these studies have been restricted to a few model plant systems. Very few drought responsive genes have been reported till date from non model drought tolerant plants. The present study aimed at identifying differentially expressed genes from a drought tolerant, non-model plant, Ziziphus nummularia (Burm.f.) Wight & Arn. One month old seedlings of Z. nummularia were subjected to drought stress by 30% Polyethylene glycol (PEG6000) treatment for 6, 12, 24, 48 and 72h. A significant reduction in RWC and increase in proline was observed at 24h and 48h of treatment. Suppression subtractive hybridization (SSH) library was constructed with drought stressed seedlings after 24h and 48h of PEG 6000 treatment. A total of 142 and 530 unigenes from 24h and 48h library were identified respectively. Gene ontology studies revealed that about 9.78% and 15.07% unigenes from 24h and 48h SSH libraries were expressed in "response to stress". Fifteen putative drought responsive genes identified in SSH library were validated for drought responsive differential expression by RT-qPCR. Significant changes in fold expressions were observed with time in the treated samples compared to the control. A heat map revealing the expression profile of genes was constructed by hierarchical clustering. Various genes identified in SSH libraries can serve as a resource for marker discovery and selection of candidate genes to improve drought tolerance in other susceptible crops.