Molecular docking of the DREB(A-6) group and enhanced thermotolerance in potato by overexpressing the DREB(A-6) gene.

Dehydration-responsive element binding (DREB) transcription factors (TFs) play an indispensable role in abiotic stress tolerance, including heat stress via abscisic acid (ABA) dependent and independent pathways. Among them, the DREB (A-6) subgroup remains least characterized, and the role of StDREB30 (A-6) under heat stress, particularly in association with ABA signaling, is not previously explored. This study aimed to characterize StDREB (A-6) group by molecular modelling and explore the role of StDREB30 in thermotolerance and its association with exogenous ABA. Molecular modelling was performed to predict 3D structures using SWISS-MODEL. STRING database was employed for protein-protein interactions (PPI), and molecular docking analysis was performed using the HDOCK server. Further, the role of StDREB30 (A-6) was assessed under heat (42 °C), ABA (50 µM), and combined (heat + ABA) treatments in potato. Overexpression of StDREB30 enhanced the tolerance in transgenic (T) potato under combined treatment of heat and ABA as compared to wild type (WT) counterparts. StDREB30 overexpressing plants showed significant upregulation of the StDREB30 gene, improved phenotypic traits and physiological features under heat and combined heat + ABA treatment. Transgenic lines maintained higher relative water content (i.e., 70% in T vs. 59% in WT), low malondialdehyde (3.1 nmol/g FW in T vs. 3.9 nmol/g FW in WT) and high anthocyanin content. It also improved photosynthetic parameters, including the maximum quantum yield of photosystem II (0.7 in T vs. 0.6 in WT), coefficient of photochemical quenching (0.6 in T vs. 0.49 in WT), and chlorophyll meter (SPAD) values (45 in T vs. 41 in WT). Moreover, RT-PCR analysis confirmed strong up-regulation of StDREB30 (i.e., 5.8, 6.1, and 7.2-fold in leaves, shoots and roots, respectively) under combined heat + ABA treatment compared to non-transgenic counterparts. The transgenic plants showed higher antioxidant activities, decreased reactive oxygen species, and cell death. Additionally, the combined (heat + ABA) treatment enhanced tuberization in transgenic plants. It is proposed that ABA primarily serves as a stress signal modulator without significantly influencing the physiological, biochemical and expression patterns under non-stressed conditions but significantly alleviates the effects of heat stress in combined treatment.