\u201cThe PLCP gene family of grapevine (Vitis vinifera L.): characterization and differential expression in response to Plasmopara Viticola\u201d

Jun Kang,Mengwei Zhang,Zhongjie Liu,Mengqing Ge,Peijie Gong,Ehsan Sadeghnezhad,Jinggui Fang,Lingfei Shangguan

doi:10.1186/s12870-021-03279-w

Abstract

BackgroundPapain-like cysteine proteases (PLCPs), a large group of cysteine proteases, are structurally related to papain. The members belonging to PLCPs family contribute to plant immunity, senescence, and defense responses in plants. The PLCP gene family has been identified in Arabidopsis, rice, soybean, and cotton. However, no systematic analysis of PLCP genes has been undertaken in grapevine. Since Plasmopara viticola as a destructive pathogen could affect immunity of grapes in the field, we considered that the members belonged to PLCPs family could play a crucial role in defensive mechanisms or programmed cell death. We aimed to evaluate the role of PLCPs in 2 different varieties of grapevines and compared the changes of their expressions with the transcriptional data in response to P. viticola.ResultsIn this study, 23 grapevine PLCP (VvPLCP) genes were identified by comprehensive bioinformatics analysis. Subsequently, the chromosomal localizations, gene structure, conserved domains, phylogenetic relationship, gene duplication, and cis-acting elements were analyzed. Numerous cis-acting elements related to plant development, hormone, and stress responses were identified in the promoter of the VvPLCP genes. Phylogenetic analysis grouped the VvPLCP genes into nine subgroups. The transcription of VvPLCP in different inoculation time points and varieties indicated that VvPLCP may have vital functions in grapevine defense against Plasmopara viticola. According to transcriptome data and qPCR analysis, we observed the increasing expression levels of VvRD21–1 at 72 h after inoculation in resistant variety, inferring that it was related to grape downy mildew resistance. Meanwhile, 3 genes including VvXBCP1, VvSAG12–1, and VvALP1 showed higher expression at 24 h after pathogen inoculation in the susceptible variety and might be related to the downy mildew phenotype. We nominated these four genes to function during hypersensitive response (HR) process, inferring that these genes could be associated with downy mildew resistance in grapes.ConclusionsOur results provide the reference for functional studies of PLCP gene family, and highlight its functions in grapevine defense against P. viticola. The results help us to better understand the complexity of the PLCP gene family in plant immunity and provide valuable information for future functional characterization of specific genes in grapevine.

Highlights

Papain-like cysteine proteases (PLCPs), a large group of cysteine proteases, are structurally related to papain
Identification of VvPLCP gene family in grapevine To identify and obtain the PLCP genes in the grapevine genome, the Arabidopsis PLCP proteins were used as a query to search against the local grapevine genome database using TBtools software
For the sake of nomenclature and consistency, these VvPLCP genes depending on their homology to the Arabidopsis PLCP members were named VvRD21–1 ~ 3, VvCEP1 ~ 2, VvXCP1 ~ 2, VvXBCP1 ~ 2, VvSAG12–1 ~ 6, VvRD19–1 ~ 5, VvALP1, VvCTB1 and VvTHI1 (Additional file 1 Table S1)

Summary

Introduction

Papain-like cysteine proteases (PLCPs), a large group of cysteine proteases, are structurally related to papain. The members belonging to PLCPs family contribute to plant immunity, senescence, and defense responses in plants. Papain-like cysteine proteases (PLCPs) are a class of proteolytic enzymes, with a catalytic cysteine as a nucleophile during proteolysis [1]. PLCPs are structurally characterized by a typical papain-like fold domain: an α-helix and β-sheet domains [2]. Both domains are linked to each other, and the catalytic triad Cys-His-Asn is formed at the two-domain interface [4]. The CEP-like subfamily members as a unique group of papain-type cysteine endopeptidases are characterized by a C-terminal KDEL motif for retention in the endoplasmic reticulum (ER). Most members in the RD21-like and XBCP-like subfamilies carry a C-terminal extension with a Pro-rich domain followed by a granulin-like domain [12]

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