Ca14-3-3 Interacts With CaWRKY58 to Positively Modulate Pepper Response to Low-Phosphorus Starvation.

Jinsen Cai,Jiayu Wen,Sheng Yang,Xueying Huang,Deyi Guan,Weiwei Cai,Yuanyuan Shi,Shuilin He,Feng Yang,Xiaoqin Xia

doi:10.3389/fpls.2020.607878

Jinsen Cai, Jiayu Wen + Show 8 more

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https://doi.org/10.3389/fpls.2020.607878

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Abstract

Low-phosphorus stress (LPS) and pathogen attack are two important stresses frequently experienced by plants in their natural habitats, but how plant respond to them coordinately remains under-investigated. Here, we demonstrate that CaWRKY58, a known negative regulator of the pepper (Capsicum annuum) response to attack by Ralstonia solanacearum, is upregulated by LPS. Virus-induced gene silencing (VIGS) and overexpression of CaWRKY58 in Nicotiana benthamiana plants in combination with chromatin immunoprecipitation (ChIP) and electrophoretic mobility shift assays (EMSA) demonstrated that CaWRKY58 positively regulates the response of pepper to LPS by directly targeting and regulating genes related to phosphorus-deficiency tolerance, including PHOSPHATE STARVATION RESPONSE1 (PHR1). Yeast two-hybrid assays revealed that CaWRKY58 interacts with a 14-3-3 protein (Ca14-3-3); this interaction was confirmed by pull-down, bimolecular fluorescence complementation (BiFC), and microscale thermophoresis (MST) assays. The interaction between Ca14-3-3 and CaWRKY58 enhanced the activation of PHR1 expression by CaWRKY58, but did not affect the expression of the immunity-related genes CaNPR1 and CaDEF1, which are negatively regulated by CaWRKY58 in pepper upon Ralstonia solanacearum inoculation. Collectively, our data indicate that CaWRKY58 negatively regulates immunity against Ralstonia solanacearum, but positively regulates tolerance to LPS and that Ca14-3-3 transcriptionally activates CaWRKY58 in response to LPS.

Highlights

Plants are confronted with fluctuating ecological environments and are often exposed to biotic or abiotic stresses
We provide evidence that in addition to acting as a negative regulator of immunity against Ralstonia solanacearum infection (RSI) in pepper, CaWRKY58 positively regulates tolerance to Low-phosphorus stress (LPS), an effect that is mediated by interaction with Ca14-3-3
The data from CaWRKY58 upregulation against LPS and the data from loss--of-function and gain-of-function assay indicate that CaWRKY58 positively regulates the response to LPS by regulating CaPHR1, which related to LPS tolerance (Motte and Beeckman, 2017; Wang et al, 2019), as well as by modulating root system architecture (RSA), a key parameter that is positively related to LPS tolerance (Jain et al, 2007; Mori et al, 2016)

Summary

Introduction

Plants are confronted with fluctuating ecological environments and are often exposed to biotic or abiotic stresses. The transcription of many transcription factor genes is altered in response to LPS; these transcription factors act as positive or negative modulators of the response and include members of the MYB (Khan et al, 2014; Zhou et al, 2017; Wang et al, 2019), WRKY (Wang et al, 2014; Su et al, 2015; Dai et al, 2016), JAZ (Jasmonate-ZIM domain) (Aparicio-Fabre et al, 2013), bHLH (Valdes-Lopez and Hernandez, 2008b), zinc-finger (Devaiah et al, 2007b; Ding et al, 2016), AP2/ERF (Ramaiah et al, 2014), CCAAT box-binding (NF-Y; Qu et al, 2015), and auxin response factor (ARF; Shen et al, 2013) families, as well as PHR1 (Motte and Beeckman, 2017; Wang et al, 2019) Some of these transcription factors might be modulated in a context-dependent manner by interacting with other regulators, such as SPX domaincontaining proteins (Zhong et al, 2018) and WRKY proteins (Zhou et al, 2017). The underlying mechanism for this crosstalk remains largely uncharacterized

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