Aquaporins are key membrane proteins that mediate water transport in plants and are indispensable for maintaining cellular water homeostasis and normal physiological processes. This study investigated the function of SbPIP1-3, an aquaporin gene isolated from drought-tolerant Sorghum bicolor. Bioinformatics analysis, subcellular localization, and heterologous expression of SbPIP1-3 were performed in Saccharomyces cerevisiae, Arabidopsis thaliana, and rapeseed. Sequence analysis revealed that SbPIP1-3 encodes a basic hydrophobic protein targeted to the plasma membrane, a finding further corroborated by subcellular localization assays. In yeast expression assays, SbPIP1-3-transformed strains retained viability under osmotic stress induced by 1.2 M mannitol, whereas non-transgenic control strains failed to survive. In Arabidopsis and rapeseed experiments, the SbPIP1-3 overexpression enhanced drought tolerance (improved germination, root growth, antioxidant enzyme activity, proline content, PSII repair capacity, and survival after drought–rewatering) and reduced intracellular H2O2 accumulation. Transcriptome profiling of drought-stressed transgenic Arabidopsis and control plants demonstrated significant upregulation of mostly stress-responsive pathways (e.g., MAPK signaling pathway and hormone signaling pathways) and key drought-tolerance genes (e.g., SNRK2-2, SOD1, APX3, GPX3, P5CS1). Collectively, these findings suggest that SbPIP1-3 enhances plant drought tolerance through the following mechanisms: improving transmembrane water transport efficiency to sustain cellular osmotic balance; activating the antioxidant defense system to increase enzyme activity and mitigate reactive oxygen species (ROS) accumulation; optimizing photosynthetic protection mechanisms to preserve the structural and functional integrity of PSII; and regulating the expression of stress-responsive signaling pathways and associated functional genes.
Gao et al. (Fri,) studied this question.