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Functional analysis of the MSP18 root-knot nematode virulence gene in rice

Diana Fernandez: IRD, CIRAD, Univ Montpellier, IPME

<div>Several root-knot nematodes (RKN) species are responsible for rice (<em>Oryza sativa</em>) production losses in Brazil, Asia or Africa. Successful infection is likely achieved by effector proteins produced in the nematode esophageal gland cells and released into host plant cells. Here we show that the <em>Meloidogyne</em> <em>incognita</em> MSP18 esophageal gland cell protein is conserved in the <em>Meloidogyne </em><em>javanica</em> and <em>Meloidogyne graminicola</em> species infecting rice. The <em>MSP18</em> gene was upregulated throughout all nematode parasitic stages in rice. Transient expression assays in onion cells suggest that MSP18 is addressed to the cytoplasm of the host cells. Overexpression of <em>MSP18</em> in rice enhanced <em>M. </em><em>javanica</em> and <em>M. graminicola</em> reproduction, indicating that the MSP18 protein facilitates RKN parasitism. Transient expression assays in tobacco showed that MSP18 suppressed the INF1-triggered programmed cell death, suggesting that MSP18 can interfere with the plant defense pathways. Data obtained significantly broaden our knowledge of molecular players contributing to nematode pathogenicity, and highlight MSP18 as a novel RKN virulence effector able to modulate host immunity.</div>