Abstract
Cotton, a natural fiber producing crop of huge importance, is often prone to attack of Verticillium dahliae. Papain-like cysteine proteases (PLCPs) constitute a large family in plants and were proposed to involve in plant defense against pathogen attack in a number of studies. However, there is no detailed characterization of PLCP genes in cotton against infection of V. dahliae. In this study, we carried out a genome-wide analysis in cotton and identified seventy-eight PLCPs, which were divided into nine subfamilies based on their evolution phylogeny: RD21 (responsive to desiccation 21), CEP (cysteine endopeptidase), XCP (xylem cysteine peptidase), XBCP3 (xylem bark cysteine peptidase 3), THI, SAG12 (senescence-associated gene 12), RD19 (responsive to desiccation 19), ALP (aleurain-like protease) and CTB (cathepsin B-like). Genes in each subfamily exhibit a similar structure and motif composition. The expression patterns of these genes in different organs were examined, and subfamily RD21 was the most abundant in these families. Expression profiles under abiotic stress showed that thirty-five PLCP genes were induced by multiple stresses. Further transcriptome analysis showed that sixteen PLCP genes were up-regulated in response to V. dahliae in cotton. Among those, GhRD21-7 showed a higher transcription level than most other PLCP genes. Additionally, over-expression of GhRD21-7 led to enhanced resistance and RNAi lines were more susceptible to V. dahliae in cotton. Our results provide valuable information for future functional genomic studies of PLCP gene family in cotton.
Highlights
Papain-like cysteine proteases (PLCPs), which belong to the family C1A of clan CA, are a class of proteolytic enzymes, with a catalytic cysteine as a nucleophile during proteolysis (Rawlings et al, 2010)
A total of 78 PLCPs were identified in G. hirsutum
These PLCPs were grouped into nine subfamilies according to their phylogenetic clade and structure features, which were similar to previous studies (Richau et al, 2012)
Summary
Papain-like cysteine proteases (PLCPs), which belong to the family C1A of clan CA, are a class of proteolytic enzymes, with a catalytic cysteine as a nucleophile during proteolysis (Rawlings et al, 2010). PLCPs are structurally characterized by a typical papain-like fold domain: an α-helix and β-sheet domain. Cysteine Proteases Medicate Defense Responses (Turk et al, 2001) Both domains are linked to each other, and the catalytic triad Cys-His-Asn forms at the two-domain interface (Turk et al, 2001). PLCPs are synthesized as preproproteases which contain a signal peptide, an auto-inhibitory pro-domain and a mature protease domain (Beers et al, 2004). After cleaving off an inhibitory pro-domain, PLCPs become active through self-processing or with the aid of processing enzymes. 723 plant PLCPs were divided into nine classes according to their homology and domain architecture (Richau et al, 2012)
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