Cloning and functional analyses of pepper CaRKNR involved in Meloidogyne incognita resistance

Root-knot nematodes (Meloidogyne spp.) are destructive pests of crops. Pepper (Capsicum annuum L.) contains genes that control resistance to root-knot nematodes. Using suppression subtractive hybridization and RACE strategies, a nucleotide-binding site and leucine-rich repeat (NBS-LRR) family gene, CaRKNR (FJ231739), was isolated and cloned from the nematode-resistant pepper line HDA149. CaRKNR is a novel NBS-LRR gene with an open reading frame of 3600 bp that is homologous (70.45 % identity) to the gene Mi-1.2. After Meloidogyne incognita inoculation, real-time qPCR showed that the CaRKNR expression level was increased from 0.63 to 2.16 times. Using the virus-induced gene silencing system, the CaRKNR gene's expression level was reduced significantly than controls, and the average numbers of galls and egg masses in silenced seedlings were 44.39 and 42.01, respectively, while the controls were 0.13. This study revealed that CaRKNR was induced by M. incognita and its expression correlated with pepper resistance against root-knot nematodes.