Aquaporin PIP2;1 affects water transport and root growth in rice (Oryza sativa L.)

Aquaporins are key proteins in regulating water transport, plant growth and development. In this study, we investigated the function of plasma membrane intrinsic proteins (PIPs) in both yeast (Saccharomyces cerevisiae) and rice (Oryza sativa cv. Nipponbare). Three OsPIP1s (OsPIP1;1, OsPIP1;2 and OsPIP1;3) and four OsPIP2s (OsPIP2;1, OsPIP2;3, OsPIP2;4 and OsPIP2;5) were successfully amplified and expressed in yeast. Overexpression of OsPIP2s, especially OsPIP2;1, increased yeast membrane water permeability (P-f). Root hydraulic conductivity (Lpr) was decreased by approximately four-fold in OsPIP2; 1 RNAi knock-down plants, resulting in a decrease in OsPIP2;1 expression levels of 70% and 50% in line 3 and line 4, respectively, compared to the wild type (WT) plants. No significant differences in the photosynthetic rate, transpiration rate, mesophyll conductance and chloroplast CO2 concentration were observed between WT and OsPIP2; 1 RNAi plants. Higher stomatal conductance and intercellular CO2 concentrations were observed in line 3 plants than in WT plants. In addition, lower root total length, surface area, root volume and fewer root tips were found in the RNAi plants than in the WT plants. Finally, the RNAi plants were more sensitive to drought stress. The results indicate that PIP2; 1 plays an important role in the regulation of water transport and plant growth.