Molecular cloning and functional analysis of the pepper resistance gene Me3 to root-knot nematode

Abstract

Root-knot nematodes (RKNs) cause severe diseases in peppers annually around the world. In pepper, the Me3 gene provides a heat-stable and broad-spectrum resistance to RKNs. In this study, several simple sequence repeat (SSR) markers and insertion/deletion (InDel) markers were developed to fine map the Me3 gene. Analysis of 2272 individuals (F2 progenies) revealed that Me3 was located in a 45-kb DNA region between markers SSR784 and SSR339, in which there were three candidate genes. Among them, as a novel nucleotide binding site and leucine rich repeat (NBS-LRR) family gene, the DNA sequence of Capana09g000163 of pepper line ‘HDA149’ was 6348 bp in length, with a 2802-bp open reading frame encoding 933 amino acids, including NB-ARC and LRR domains. Tobacco transient expression assays demonstrated that expression of Capana09g000163 triggered a hypersensitive response (HR) in Nicotiana benthamiana leaves. Subcellular localization results showed that the Capana09g000163 protein was localized in the cell nucleus. Ectopic expression of Capana09g000163 in Arabidopsis significantly increased resistance against Meloidogyne incognita compared with the wild-type (WT) Arabidopsis. Furthermore, M. incognita was almost unable to develop in transgenic Arabidopsis expressing Capana09g000163. Taken together, we cloned the Me3 gene and verified that it induced resistance against M. incognita with the methods of map-based cloning and transgenic technology, which may be of great significance to pepper breeding for resistance against RKNs.