Exogenous application of γ-aminobutyric acid alleviates temperature stress in mungbean (Vigna radiata) and its wild non-progenitor (Vigna glabrescens) by regulating heat shock protein genes

Abiotic stresses significantly affect plant growth and productivity. Identification of stress-tolerant genotypes is the best and an effective mitigation strategy. The present study evaluates the thermosensitive Vigna radiata cv. Shikha and the thermotolerant Vigna glabrescens accession TCR-20 under the control (non stress), cold stress, and heat stress conditions, without any treatment or foliar treatment with indole-3-acetic acid (IAA), salicylic acid (SA), or gamma-aminobutyric acid (GABA). Chlorophyll content revealed that TCR-20 maintained higher chlorophyll content under stress, whereas Shikha exhibited higher chlorophyll content upon foliar spray of GABA. Histochemical staining confirmed an increased oxidative stress under extreme temperatures, with GABA effectively mitigated the hydrogenperoxide and superoxide accumulation in both genotypes. Further, mining and comparative analysis of 96 heat shock proteins (HSPs), including HSP20, HSP60, HSP70, HSP90, and HSP100 were also done. Physicochemical characterization revealed varied stability, solubility, and thermostability of these proteins, which exhibited higher stress tolerance potential. All 96 HSPs were found widespread across the 11 chromosomes. Notably, the HSP70 family, particularly VrHSP-70.2 in TCR-20, exhibited the most robust response under both cold and heat stress, with significant upregulation, especially with GABA followed by IAA treatments. The genes such as VrHSP-70.2, VrHSP-60.22, and VrHSP-20.24 highlighted their significant upregulations in TCR-20 over Shikha. Overall, these findings provide valuable insights into the molecular and physiological mechanisms underlying thermotolerance in Vigna species, emphasizing the role of HSPs and stress-mitigating treatments for improving stress resilience in Vigna crops.