Long term transcript accumulation during the development of dehydration adaptation in Cicer arietinum.

Cool season crops face intermittent drought. Exposure to drought and other abiotic stresses is known to increase tolerance of the plants against subsequent exposure to such stresses. Storage of environmental signals is also proposed. Preexposure to a dehydration shock improved adaptive response during subsequent dehydration treatment in a cool season crop chickpea (Cicer arietinum). We have identified 101 dehydration-inducible transcripts of chickpea by repetitive rounds of cDNA subtraction; differential DNA-array hybridization followed by northern-blot analysis and analyzed their responses to exogenous application of abscisic acid (ABA). Steady-state expression levels of the dehydration-induced transcripts were monitored during the recovery period between 2 consecutive dehydration stresses. Seven of them maintained more than 3-fold of expression after 24 h and more than 2-fold of expression level even at 72 h after the removal of stress. Noticeably, all of them were inducible by exogenous ABA treatment. When the seedlings were subjected to recover similarly after an exposure to exogenous ABA, the steady-state abundances of 6 of them followed totally different kinetics returning to basal level expression within 24 h. This observation indicated a correlation between the longer period of abundance of those transcripts in the recovery period and improved adaptation of the plants to subsequent dehydration stress and suggested that both ABA-dependent and -independent mechanisms are involved in the maintenance of the messages from the previous stress experience.