Abstract
The aim of this work was to study the regulation of coffee DREB-like genes in leaves of C. arabica subjected to cold, heat, low relative humidity, exogenous abscisic acid and high light stress, as well as in leaves and roots of drought-tolerant and drought-susceptible clones of Coffea canephora subjected to water limitation. In C. arabica, CaERF017 was the most expressed gene under low temperatures and relative humidity, while low humidity and high temperatures up-regulated the expression of CaERF053 and CaERF014, respectively. Under water limitation, CcDREB1B, CcRAP2.4, CcERF027, CcDREB1D and CcTINY were the most expressed genes mainly in leaves of drought-tolerant C. canephora. On the other hand, expression of the CcERF016, CcRAP2.4 and CcDREB2F genes was highly up-regulated under water limitation in the roots of drought-susceptible C. canephora clone 22. We previously reported fine-tuned regulation of CcDREB1D promoter haplotypes (HP15, HP16 and HP17) in transgenic C. arabica subjected to low humidity. Here, we investigated the regulation of these haplotypes under high light, cold, heat, and abscisic acid (ABA) stress. In apical buds and leaf guard cells, GUS-stained percentages were higher in pHP16L-transformed plants subjected to low humidity, high light and ABA stress than in pHP17L- and pHP15L-transformed plants. We also reported up-regulated expression of the endogenous CaDREB1D gene for both the cold and low humidity in leaves of pHP16L-transformed C. arabica suggesting a key role of this gene in controlling the responses of coffee plants to abiotic stress probably through an ABA-dependent pathway.