Abstract
Root-knot nematodes (RKNs) are devastating parasites that infect thousands of plants. As RKN infection is facilitated by oesophageal gland effector genes, one such effector gene, Mi-msp2, was selected for a detailed characterization. Based on domain analysis, the Mi-MSP2 protein contains an ShKT domain, which is likely involved in blocking K+ channels and may help in evading the plant defence response. Expression of the Mi-msp2 gene was higher in juveniles (parasitic stage of RKNs) than in eggs and adults. Stable homozygous transgenic Arabidopsis lines expressing Mi-msp2 dsRNA were generated, and the numbers of galls, females and egg masses were reduced by 52–54%, 60–66% and 84–95%, respectively, in two independent RNAi lines compared with control plants. Furthermore, expression analysis revealed a significant reduction in Mi-msp2 mRNA abundance (up to 88%) in female nematodes feeding on transgenic plants expressing dsRNA, and northern blot analysis confirmed expression of the Mi-msp2 siRNA in the transgenic plants. Interestingly, a significant reduction in the reproduction factor was observed (nearly 40-fold). These data suggest that the Mi-msp2 gene can be used as a potential target for RKN management in crops of economic importance.
Highlights
Attacking more than 2000 plant species and leading to crop losses of 173 billion USD annually in worldwide agriculture, root-knot nematodes (RKNs; Meloidogyne spp.) are among the most injurious plant parasitic nematodes (PPNs)[1]
A genome-wide NCBI-BLAST analysis of the Mi-msp[2] gene sequence revealed it to be specific to M. incognita, with no sequence orthologues found in the NCBI redundant database
Structural analyses of the Mi-MSP2 protein revealed the presence of two structural classifications of proteins (SCOP) domains, SCOP:d0c3a and SCOP:d1|1|a, and one ShK toxin domain comprising 37 amino acids (Fig. 1c)
Summary
Attacking more than 2000 plant species and leading to crop losses of 173 billion USD annually in worldwide agriculture, root-knot nematodes (RKNs; Meloidogyne spp.) are among the most injurious plant parasitic nematodes (PPNs)[1]. Effector proteins that are produced in a granulated form in the oesophageal glands (secretory proteins) are transferred to plant cells via the stylet[6] These proteins are essential for the onset and maintenance of parasitism and are mainly associated with three functions: (i) facilitation of migration, (ii) defence against plant responses and (iii) establishment and maintenance of permanent feeding sites through manipulation of the host cellular machinery[7]. 37 putative effectors have been identified and localized subcellularly as proteins that are secreted by the subventral and dorsal oesophageal glands in M. incognita[26] As characterization of these effectors will lead to improved understanding of the molecular basis of M. incognita parasitism, in this study, we characterized one such M. incognita effector gene, Mi-msp[2] (for Meloidogyne secretory protein), as previously reported by Huang et al.[26]. Using HD-RNAi technology, transgenic Arabidopsis thaliana lines expressing Mi-msp[2] dsRNA were employed to promote nematode resistance
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