Overexpression of Water-Responsive Genes Promoted by Elevated CO Reduces ROS and Enhances Drought Tolerance in Species.

Drought is a major constraint to plant growth and productivity worldwide and will aggravate as water availability becomes scarcer. Although elevated air [CO] might mitigate some of these effects in plants, the mechanisms underlying the involved responses are poorly understood in woody economically important crops such as . This study analyzed transcriptome changes in cv. CL153 and cv. Icatu exposed to moderate (MWD) or severe water deficits (SWD) and grown under ambient (aCO) or elevated (eCO) air [CO]. We found that changes in expression levels and regulatory pathways were barely affected by MWD, while the SWD condition led to a down-regulation of most differentially expressed genes (DEGs). eCO attenuated the impacts of drought in the transcripts of both genotypes but mostly in Icatu, in agreement with physiological and metabolic studies. A predominance of protective and reactive oxygen species (ROS)-scavenging-related genes, directly or indirectly associated with ABA signaling pathways, was found in responses, including genes involved in water deprivation and desiccation, such as protein phosphatases in Icatu, and aspartic proteases and dehydrins in CL153, whose expression was validated by qRT-PCR. The existence of a complex post-transcriptional regulatory mechanism appears to occur in explaining some apparent discrepancies between transcriptomic, proteomic, and physiological data in these genotypes.