Abstract
A germin-like gene (CchGLP) cloned from geminivirus-resistant pepper (Capsicum chinense Jacq. Line BG-3821) was characterized and the enzymatic activity of the expressed protein analyzed. The predicted protein consists of 203 amino acids, similar to other germin-like proteins. A highly conserved cupin domain and typical germin boxes, one of them containing three histidines and one glutamate, are also present in CchGLP. A signal peptide was predicted in the first 18 N-terminal amino acids, as well as one putative N-glycosylation site from residues 44–47. CchGLP was expressed in E. coli and the recombinant protein displayed manganese superoxide dismutase (Mn-SOD) activity. Molecular analysis showed that CchGLP is present in one copy in the C. chinense Jacq. genome and was induced in plants by ethylene (Et) and salicylic acid (SA) but not jasmonic acid (JA) applications in the absence of pathogens. Meanwhile, incompatible interactions with either Pepper golden mosaic virus (PepGMV) or Pepper huasteco yellow vein virus (PHYVV) caused local and systemic CchGLP induction in these geminivirus-resistant plants, but not in a susceptible accession. Compatible interactions with PHYVV, PepGMV and oomycete Phytophthora capsici did not induce CchGLP expression. Thus, these results indicate that CchGLP encodes a Mn-SOD, which is induced in the C. chinense geminivirus-resistant line BG-3821, likely using SA and Et signaling pathways during incompatible interactions with geminiviruses PepGMV and PHYVV.
Highlights
Germins and germin-like proteins (GLPs) have been implicated in the reinforcement of plant cell wall strength providing plants with resistance to biotic and abiotic stresses [1,2,3]
The deduced protein of CchGLP was more related to a GLP of Nicotiana tabacum (93% identity, accession number: BAH15357)
Accession numbers of GLP amino acid sequences evaluated in the tree are: C chinense (ABG76199), A. thaliana (NP_177405), Auxin binding protein from Solanum nigrum (ADW66138), GLP 24 K from Nicotiana tabacum (BAC77634), GLP from Nicotiana tabacum (BAH15357), Auxin binding protein from Solanum nigrum (ADW66150) and auxin binding protein 19a from Prunus persica (Q9ZRA4)
Summary
Germins and germin-like proteins (GLPs) have been implicated in the reinforcement of plant cell wall strength providing plants with resistance to biotic and abiotic stresses [1,2,3]. A key feature of the GLP-related subfamilies, including germins, is the presence of germin boxes and conservation of a cupin superfamily (beta-barrel proteins) derived-motif [4,5,6,7]. This motif contains three highly conserved histidines and one glutamate residue involved in binding a metal ion [8]. OXO and SOD activities result in production of hydrogen peroxide. A new GLP gene (hereafter named as CchGLP) was previously identified in a geminivirus-resistant Capsicum chinense line named BG-3821 [11,12]. CchGLP is induced in incompatible interactions of C. chinense
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