Versatile roles of aquaporin in physiological processes and stress tolerance in plants

Aquaporins are pore-forming transmembrane proteins that facilitate the movement of water and many other small neutral solutes across the cells and intracellular compartments. Plants exhibits high diversity in aquaporin isoforms and broadly classified into five different subfamilies on the basis of phylogenetic distribution and subcellular occurrence: plasma membrane intrinsic proteins (PIPs), tonoplast intrinsic proteins (TIPs), nodulin 26-like proteins (NIPs), small basic intrinsic proteins (SIPs) and uncharacterized intrinsic proteins (XIPs). The gating mechanism of aquaporin channels is tightly regulated by post-translational modifications such as phosphorylation, methylation, acetylation, glycosylation, and deamination. Aquaporin expression and transport functions are also modulated by the various phytohormones-mediated signalling in plants. Combined physiology and transcriptome analysis revealed the role of aquaporins in regulating hydraulic conductance in roots and leaves. The present review mainly focused on aquaporin functional activity during solute transport, plant development, abiotic stress response, and plant-microbe symbiosis. Genetically modified plants overexpressing aquaporin-encoding genes display improved agronomic and abiotic stress tolerance.