A small heat shock protein from Arabidopsis thaliana regulates glyceraldehyde-3-phosphate dehydrogenase in the drought tolerance.

HSP17.4 improves tolerance of Arabidopsis to drought via interaction with GAPC2. Small heat shock proteins (sHSPs) are a widespread family of molecular chaperones, highly conserved from bacteria to higher eukaryotes, contributing to plant adaptation to environmental stresses. However, the specific mechanisms underlying sHSP-mediated drought tolerance remain poorly understood. In this study, we found that HSP17.4 (At3G46230), a member of the predominant cytosolic class I (CI) sHSPs in Arabidopsis thaliana, was drought-inducible. Overexpression of HSP17.4 in both Arabidopsis and Oryza sativa improved drought tolerance, accompanied by elevated glucose and abscisic acid (ABA) levels, enhanced superoxide dismutase (SOD) and peroxidase (POD) activities, and reduced malondialdehyde (MDA) and H2O2 accumulation. Transcriptomic data along with real-time PCR verified that the transcript abundance of genes associated with sugar transport and ABA biosynthesis was significantly upregulated in HSP17.4-overexpressing Arabidopsis compared to wild-type plants. Yeast two-hybrid screening identified Arabidopsis glyceraldehyde-3-phosphate dehydrogenase GAPC2 (AT1G13440) as an interacting partner of HSP17.4, an association further validated by pull-down and bimolecular fluorescence complementation (BiFC) assays. HSP17.4 exhibited in vitro chaperone activity toward GAPC2. Furthermore, reduced GAPC2 expression in A. thaliana led to enhanced drought sensitivity and impaired glucose uptake, while exogenous glucose application promoted ABA accumulation and drought tolerance. These findings suggested that HSP17.4 acted as a molecular chaperone to stabilize GAPC2, thereby promoting drought tolerance in Arabidopsis. Overall, this study enriched our understanding of sHSP function and offered a potential strategy for engineering drought-tolerant crops.