Characterization of the psoRPM1 gene for resistance to root-knot nematodes in wild myrobalan plum (Prunus sogdiana)
Several root-knot nematode (Meloidogyne spp.) resistance genes have been discovered in different stone fruit crops. However, none of them has yet been cloned and they were only located on the chromosomes. In this study, a candidate root-knot nematode resistance gene (designated as psoRPM1) was isolated from the individual plant of Xinjiang wild myrobalan plum (Prunus sogdiana) by degenerate PCR amplification combined with the RACE technique. The gene had a typical NBS-LRR structure and high homology with Mi-1.2 (root-knot nematode resistance genes in tomato). The expression of psoRPM1 gene increased in the roots of resistant wild myrobalan plum material 12, 24 and 48 h after inoculation with root-knot nematodes and the expression of psoRPM1 gene was maximum 12 h after inoculation. But in susceptible plant, the psoRPM1 gene expression remained low both before and after inoculation. This result suggested that the psoRPM1 gene was constitutively expressed gene in the wild myrobalan plum. In-situ hybridization results showed that the psoRPM1 gene mainly expressed in both phloem and cortex parenchyma of root 12 h after inoculation in resistant plant. Furthermore, the psoRPM1 gene only expressed in phloem 48 h after inoculation in resistant plant. The result suggested that the psoRPM1 gene played a role in keeping nematodes off the cortex when nematodes began to infect the plant’s roots. After root-knot nematodes entering into cortex parenchyma, the psoRPM1 gene mainly played defense function in phloem of pericycle. Using the gene gun bombarding into onion epidermal cells, the result was that psoRPM1 protein was located in cytomembrane and might be interacted with other proteins in cytomembrane to locate
Key words: Xingjiang wild myrobalan plum (Prunus sogdiana), root-knot nematodes (Meloidogyne incognita), gene, in-situ, gene location.