The Small GTPase RHO1 Regulates ROS Homeostasis and Differentially Responds to Pathogens Infection via Interaction With Aquaporin TIP1;1 in Nicotiana.

Small G-proteins are crucial regulators in plant growth and environmental responses. However, the mechanistic basis underlying their regulation of plant immunity to different pathogens is still poorly understood. Here, we showed that the small GTPase Ras homologous 1 (RHO1) responded differently to infection by distinct pathogens. Overexpression of RHO1 increased the plant susceptibility to chilli veinal mottle virus (ChiVMV) and necrotrophic Botrytis cinerea infections but enhanced plant resistance to the biotrophic bacterium Pseudomonas syringae. Further exploration revealed that there existed a direct interaction between RHO1 and tonoplast intrinsic protein 1;1 (TIP1;1), an aquaporin involved in water movement and the transport of hydrogen peroxide (H2O2) between vacuoles and cytoplasm. Under pathogen infection, the interaction between RHO1 and TIP1;1 could affect the distribution of reactive oxygen species (ROS) in the cytoplasm and vacuoles, promote the accumulation of ROS in the cytoplasm, leading to different responses of plant cells to pathogens with different lifestyles. Furthermore, the expression level of TIP1;1 was altered under infection by different pathogens. Our results demonstrate a mechanism by which the small GTPase RHO1 regulates ROS compartmentalization to affect the plant response to different pathogen infections, indicating the diversity of responses of a plant gene to different biotic factors.