Aquaporin-mediated stress signaling cascade in plants

Environments affected plant growth and development, while their change resulted in various stresses in higher plants. Aquaporins (AQPs) were the major intrinsic proteins (MIPs), which participated in the water channel, and kept the water balance for cells both inside and outside. This review focused on category, structure, regulation and stress responses of AQPs in higher plants. Briefly, AQPs were made up of five loop structures that connected with six alpha-helical transmembrane structures, and contained two Asn-Pro-Ala (NPA-motifs). They could be divided into eight subfamilies, and in higher plants, research concentrated mainly on plasma membrane intrinsic proteins (PIPs), tonoplast membrane intrinsic proteins (TIPs), nodulin26-like major intrinsic proteins (NIPs) and small and basic intrinsic proteins (SIPs). It is interesting that AQPs involved in water, nutrition, CO2 and H2O2 transport, and were a part of regulatory elements for biotic and abiotic stress responses. Furthermore, the activity of AQPs was affected by the transcriptional regulation, protein modification, potential of hydrogen (pH) and signal transduction. Taken together, we highlight the research progress of AQPs in higher plants, and forecasts the function model of AQPs in biotic and abiotic stresses, which should be helpful for further investigation on AQPs-mediated stress signaling cascade in higher plants.