Physiological and molecular studies of different aldehyde dehydrogenase (<i>ALDH</i>) genes in response to high temperature and functional analyses of the <i>ALDH7B4</i> promoter in <i>Arabidopsis thaliana</i>

Abstract

In this study, the function of aldehyde dehydrogenase (<i>ALDH</i>) genes in response to heat stress alone and in combination with dehydration, salinity, or wounding stress was investigated using selected <i>ALDH</i> genes and characterized transgenic <i>A. thaliana ALDH </i> double knock-out lines. As heat stress often occurs in combination with other stresses, the purpose of this study was to first investigate the response of selected <i>ALDH</i> genes to heat and secondly to a combination of heat and other abiotic stresses. Expression of selected <i>ALDH</i> genes was analyzed on the transcript and protein level at different time points of heat stress and in response to basal or acquired thermotolerance. The results showed that <i>ALDH</i> genes, particularly ALDH7B4, is strongly induced by heat and combination stresses, indicating that <i>ALDH</i> genes play a crucial role in protecting plants from high temperature damages. The comparison of the physiological and biological parameters (survival rates, photosynthesis, lipid peroxidation and chlorophyll content) in T-DNA double mutants of <i>ALDH</i> genes and wild-type plants demonstrated that mutant lines are more sensitive to heat and combination stresses. DRE/CRT and ACGT1 motifs in <i>ALDH7B4</i> promoter are vital for the response to heat stress combined with wounding or salt stress. In addition, ACGT2 and ACGT3 promoter elements play a crucial role for <i>ALDH7B4</i> gene expression and stress responsiveness. Using a yeast one-hybrid screen and EMSA technique demonstrated that ATAF1 activates <i>ALDH7B4</i> by directly binding to a specific promoter region in vivo and in vitro. Moreover, ATAF1 acts as a DNA-binding transcription activator that involved in <i>ALDH7B4</i> expression in different growth stages.