AtPR5K2, a PR5-Like Receptor Kinase, Modulates Plant Responses to Drought Stress by Phosphorylating Protein Phosphatase 2Cs.

Dongwon Baek,Sang Yeol Lee,Hee Jin Park,Bokyung Park,Ray A Bressan,Dhinesh Kumar,Wonkyun Choi,Min Chul Kim,Dae-Jin Yun,Mi Sun Cheong,Hyeong Cheol Park,Hyun Jin Chun,Jae-Yean Kim

doi:10.3389/fpls.2019.01146

Abstract

Cell surface receptors perceive signals from the environment and transfer them to the interior of the cell. The Arabidopsis thaliana PR5 receptor-like kinase (AtPR5K) subfamily consists of three members with extracellular domains that share sequence similarity with the PR5 proteins. In this study, we characterized the role of AtPR5K2 in plant drought-stress signaling. AtPR5K2 is predominantly expressed in leaves and localized to the plasma membrane. The atpr5k2-1 mutant showed tolerance to dehydration stress, while AtPR5K2-overexpressing plants was hypersensitive to drought. Bimolecular fluorescence complementation assays showed that AtPR5K2 physically interacted with the type 2C protein phosphatases ABA-insensitive 1 (ABI1) and ABI2 and the SNF1-related protein kinase 2 (SnRK2.6) proteins, all of which are involved in the initiation of abscisic acid (ABA) signaling; however, these interactions were inhibited by treatments of exogenous ABA. Moreover, AtPR5K2 was found to phosphorylate ABI1 and ABI2, but not SnRK2.6. Taken together, these results suggest that AtPR5K2 participates in ABA-dependent drought-stress signaling through the phosphorylation of ABI1 and ABI2.

Highlights

Plant receptors perceive signals from external stimuli and transmit this information to the interior of the cell (McCarty and Chory, 2000)
Fluorescence signals were detected in the plasma membrane of the epidermal cells coexpressing AtPR5K2VN and SNF1-related protein kinase 2s (SnRK2s).6VC (Figure 4C); no interaction was detected between AtPR5K2VN and PYL1VC (Figure 4D). These results suggest that AtPR5K2 plays an important role in the regulation of abscisic acid (ABA) core signaling by interacting with the phosphatase type 2C (PP2C) and SnRK2.6
We performed in-gel kinase assays using ABI1S314A and ABI2S304A as substrates for the AtPR5K2 kinase domain (Figure 6), revealing that their phosphorylation by wPR5K2KD was greatly attenuated in comparison with the wild type (WT) ABA-insensitive 1 (ABI1) and ABI2 proteins (Figure 6). These results suggested that AtPR5K2 phosphorylates the ABI1 and ABI2 phosphatases to modulate their activities during ABA core signaling

Summary

Introduction

Plant receptors perceive signals from external stimuli and transmit this information to the interior of the cell (McCarty and Chory, 2000). To sense and transmit the vast numbers of signals arising from environmental stimuli, plants have functionally evolved a large family of membrane receptor kinases and receptor-like kinases (RLKs) (Shiu and Bleecker, 2001; Hohmann et al, 2017). Plant RLKs have different functions according to the types of motifs in their extracellular domains (Shiu and Bleecker, 2001); for example, the extracellular domains of leucine-rich repeat RLKs (LRR-RLKs) play important roles in the protein–protein interactions required for various signal transduction pathways in plant growth and development (Kobe and Deisenhofer, 1994; Torii et al, 1996; Clark et al, 1997; Yokoyama et al, 1998; Schoof et al, 2000; Mandel et al, 2016). The pathogenesisrelated 5 (PR5) RLKs (PR5Ks) are activated by several hormones and pathogenic infections (Thomma et al, 1998; Clarke et al, 2000; Durrant and Dong, 2004; van Loon et al, 2006)

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