Harpin Hpa1 Interacts with Aquaporin PIP1;4 to Promote the Substrate Transport and Photosynthesis in Arabidopsis.

Liang Li,Wei Sun,Haiying Cui,Dan Shen,Zhonglan Xia,Fengli Sun,Hansong Dong,Jaume Flexas,Yanjuan Chen,Hongtao Ji,Zhengjiang Qian,Jorge Gago,Qing Ye,Shan Tian,Hao Wang,Naomi Kodama

doi:10.1038/srep17207

Abstract

Harpin proteins produced by plant-pathogenic Gram-negative bacteria are the venerable player in regulating bacterial virulence and inducing plant growth and defenses. A major gap in these effects is plant sensing linked to cellular responses, and plant sensor for harpin Hpa1 from rice bacterial blight pathogen points to plasma membrane intrinsic protein (PIP). Here we show that Arabidopsis AtPIP1;4 is a plasma membrane sensor of Hpa1 and plays a dual role in plasma membrane permeability of CO2 and H2O. In particular, AtPIP1;4 mediates CO2 transport with a substantial contribute to photosynthesis and further increases this function upon interacting with Hpa1 at the plasma membrane. As a result, leaf photosynthesis rates are increased and the plant growth is enhanced in contrast to the normal process without Hpa1-AtPIP1;4 interaction. Our findings demonstrate the first case that plant sensing of a bacterial harpin protein is connected with photosynthetic physiology to regulate plant growth.

Highlights

Harpins belong to a unique group of proteins secreted by the type III secretion system in plant-pathogenic Gram-negative bacteria[1,2,3]
The third effect of some harpins is to serve as type III translocators, which are distinct in nature but function to mediate translocation of type III effectors from bacterial cells into the cytosol of plant cells presumably by recognizing plasma membranes (PMs) sensors[2,18]
We have explored plant sensing of Hpa[1] and associated cellular pathways that regulate the bacterial virulence on rice and regulate both growth enhancement and immune responses of Arabidopsis[2,6,14,15,35]

Summary

Introduction

Harpins belong to a unique group of proteins secreted by the type III secretion system in plant-pathogenic Gram-negative bacteria[1,2,3]. Plant PMs must contain receptors that perceive the PM-anchored Hpa[1] signal and transmit it to the cognate cellular pathways In agreement with this hypothesis, recently we disclosed that Hpa[1] expressed in yeast directly interacted with aquaporin (AQP) OsPIP1;3 from rice[2]. As PMs directly face environment, PIPs are implicated in cellular responses to a variety of extracellular signals in addition to substrate transport[2,21,29,32,35]. This functional flexibility potentially enables certain PIP isoforms to sense microbial patterns like harpins[2,35]

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Results

Conclusion