Physiological response to drought and genome wide characterization of PYL-PP2C genes in Eucalyptus spp.

Climate change has intensified droughts, affecting Eucalyptus productivity. These species are water-demanding and understanding their ABA-mediated stomatal closure mechanisms is key to improve drought response through PYL and PP2C gene regulation. This study analyzed the physiological responses to drought in two Eucalyptus genotypes (G1 and G2) and characterized PYL and PP2C genes, including expression analysis and Genome-wide structure. G2 exhibited greater physiological stability and more efficient stomatal regulation under drought conditions, whereas G1 showed increased vulnerability. A total of 11 EglPYL were identified and mapped across six chromosomes the E. globulus genome. Gene structure and motif analysis of EglPYLs identified three conserved motifs, including two START domains, which are characteristic of ABA receptor function. Seven genes lacked introns, while four had two, highlighting structural diversity within the gene family. The EglPP2C family in E. globulus comprises 13 members, distributed between chromosomes 2 and 11. All identified genes contain at least one conserved motif characteristic of the PP2C superfamily. Notably, their gene structures exhibit considerable variation, indicating substantial structural divergence within the family. The expression of EglPYL4.1 in G2 was upregulated on day 7 of water deficit but not day 14, whilst in G1, the transcript was similar to the control on day 7 but was downregulated on day 14. This pattern is consistent with the physiological response observed in both genotypes during the water stress assay. As conclusion, G2 may represent a more suitable genotype for reforestation or forestry production programs in drought-prone environments.