The role of Arabidopsis aldehyde dehydrogenase genes in response to high temperature and stress combinations.

Aldehyde dehydrogenases (ALDH) are a family of enzymes that are involved in plant metabolism and contribute to aldehyde homeostasis to eliminate toxic aldehydes. The ALDH enzymes produce NADPH and NADH in their enzymatic reactions and thus contribute to balancing redox equivalents. Previous studies showed that Arabidopsis ALDH genes are expressed in response to high salinity, dehydration, oxidative stress, or heavy metals, suggesting important roles in environmental adaptation. However, the role of ALDH genes in high temperature and stress combinations (heat stress combined with dehydration, wounding, or salt stress) is unclear. Here, we analysed expression patterns of selected ALDH genes on the transcript and protein level at different time points of heat stress, basal and acquired thermotolerance, and stress combination treatments. Our results indicate that ALDH3I1 and ALDH7B4 are strongly induced by heat stress. Higher levels of ALDH7B4 accumulated in response to dehydration-heat, heat-salt and wounding-heat combination stress than in response to single stressors. The comparison of physiological and biological parameters in T-DNA double mutants of ALDH genes and wild-type plants demonstrated that mutant lines are more sensitive to heat stress and stress combinations than wild-type plants.