Development of transgenic tolerance in Solanum tuberosum against abiotic stress(es) by overexpression of DREB gene

Abstract

Potato is one of the most important food crops because of its rich nutritional value, high yield, and consumption, and due to its role as a global food source. However, potato suffers annual losses in terms of yield and production due to water deficiency and high salinization of cultivable land. Dehydration responsive element binding transcription factors play a major role in modulating plant defense signaling pathways and regulating various downstream stress-responsive genes in response to major abiotic stresses. Thus, these genes are instrumental in minimizing the losses due to abiotic stresses, furthermore, overexpression of genes can generate multi-stress tolerant crop plants. In the current study, a comprehensive study was performed to investigate the role of the StDREB30 gene, a member of the A-6 group of DREB factors in providing tolerance to potato plants against drought, osmotic and salt stress. Multiple sequence alignment and phylogenetic analysis of DREB genes were performed by retrieving amino acid sequences of DREB genes from A1-A6 subgroups. Furthermore, protein-protein interactions of potato DREB genes were studied, and their active catalytic site and disordered regions were predicted. StDREB30 gene belonging to the A-6 subgroup was amplified from the potato genome, purified, and cloned in binary plant expression vector pCAMBIA 1301 under the control of the Cauliflower mosaic virus 35S promoter. The resulting pCAMBIA1301::StDREB30 construct was overexpressed to produce stable transgenic potato plants through Agrobacterium mediated transformation. The results of 14 days of water withholding stress treatment and 24 hrs of 20% PEG 6000 osmotic stress on potato plants showed that transgenic potato plants overexpressing StDREB30 gene (OE) plants withstand drought and osmotic stress more efficiently with no signs of wilting while non-transgenic control plants (NT) exhibited severe wilting and stunted growth. OE potato plants thrived during drought stress, they showed vigorous growth, high biochemical activities and low malondialdehyde activity, and significantly high expression of StDREB30 gene at the end of drought stress as compared to controls. The results of salt stress further validated the role of the StDREB30 gene as a highly responsive gene against abiotic stresses. The results of 15 days of 100 and 200 mM salt stress concentrations on OE and NT plants established OE plants as multistress tolerant potato plants. Transgenic potato plants showed elevated growth, high fresh weight and continued to produce microtubers during salt stress conditions. Contrary to this, control plants showed poor growth, low weight, and failed to produce microtubers under stress conditions. The antioxidant analysis showed high superoxide dismutase, catalase, and ascorbic peroxidase activity in OE plants and a decrease in malondialdehyde activity depicting less lipid peroxidation. The expression profiling results were in parallel with the antioxidant results as the StDREB30 gene showed 52 folds, 15 folds, and 24 folds in tissues of overexpressive roots, shoots, and leaves after 15 days of salt stress as compared to control plants. Thus, these results augment the role of the StDREB30 gene in providing better tolerance to transgenic potato plants against drought, osmotic, and salt stress conditions.