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

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.

Plant Aquaporin AtPIP1;4 Links Apoplastic H2O2 Induction to Disease Immunity Pathways

“…Moreover, as PMs directly face the environment, PIPs are also implicated in cellular responses to a variety of extracellular signals in addition to substrate transport (Gomes et al, 2009;Dong, 2015a, 2015b;Li et al, 2015). Thus, a particular PIP must be subject to multiple mechanisms for functional regulation, at the transcriptional and posttranscriptional levels, for example (Maurel, 2007;Gomes et al, 2009).…”

“…1C, bar graph). We complemented atpip1;4 with the wild-type AtPIP1;4 gene fused to the coding sequence of GFP and generated transgenic atpip1;4/AtPIP1;4 lines (Li et al, 2015). Three lines were characterized to resemble the wild type in AtPIP1;4 expression ( Fig.…”

“…1D). We also transformed the wild-type plant with the AtPIP1;4-GFP fusion gene and created AtPIP1;4-overexpressing WT/AtPIP1;4 lines (Li et al, 2015). Three WT/AtPIP1;4 lines were characterized based on the overexpression of AtPIP1;4 (Fig.…”

“…leaf size) and immunity (such as SAR) reported previously (Wang et al, 2007). Since AtPIP1;4 affects the growth of every leaf on a single plant (Li et al, 2015), it is improper to test the immune responses of the different genotypes by using leaves with equivalent size; instead, we used leaves with different sizes but the same position on plants.…”

“…For example, the harpin Hpa1 from rice (Oryza sativa) bacterial blight pathogen (Zhu et al, 2000) recognizes a rice PIP1 isoform to regulate virulence (Ji and Dong, 2015a). In Arabidopsis (Arabidopsis thaliana), externally applied or de novo-expressed Hpa1 is located at the PMs (Li et al, 2015) and acts as a PAMP to induce apoplastic H 2 O 2 production through the NOX activity (Sang et al, 2012). Then, a large proportion of apoplastic H 2 O 2 moves into the cytoplasm to enhance plant resistance to the virulent strain DC3000 of Pseudomonas syringae pv tomato (DC3000).…”