Root-Knot Nematodes: Insights Into Their Parasitism and Lipid Diet

Leah Nicole Morrison

doi:10.7273/000006959

Plant parasitic nematodes are destructive pathogens with devastating effects on agricultural production. Root-knot nematodes (RKNs, Meloidogyne spp.) are particularly damaging to agriculture and the economy due to the production of galls on the roots of hosts in addition to their global distribution and wide host ranges. While chemical controls can be extremely effective at RKN control, the phasing out of commonly used nematicides has led to the search for new resistant options. Altering a sterol biosynthesis pathway has been suspected to interfere with the parasitism of plant-parasitic nematodes (PPNs), as they don’t produce their own sterols, but rather require them from their diet. By targeting the mevalonate pathway (MVA), a precursor to sterol production, I aimed to alter the food supply of RKNs to suppress parasitism. A knockdown in HMGR2, an enzyme that catalyzes the production of mevalonate revealed an increase in RKN infection. A lack of difference in second-stage juveniles in the root tissue implies HMG-CoA reductase (HMGR) has a role in feeding site formation, but not initial penetration into host roots. Another option for nematode control is to silence genes that are crucial for their parasitism. Building upon previous Gleason lab work, I selected an RKN candidate effector for characterization to provide insights into their parasitism. Analysis of candidate Meloidogyne chitwoodi effector Mc2397 revealed an NHL_PAL_like domain, which is responsible for neurological processes in animals. A BLASTp search revealed homologs in two other RKN species as well as in a migratory endoparasitic nematode. The novel sequence indicates high specialization of the protein within PPNs, something that’s indicative of effectors. The silencing of this gene via host- induced gene silencing (HIGS) revealed a significant reduction in galling upon M. chitwoodi infection. The results of my HMGR project indicate that a knockdown in HMGR2 expression affects RKN parasitism. Further studies are needed to investigate the relationship between alterations of downstream sterols and RKN infection. My second research project revealed a role of Mc2397 in parasitism. Further characterization of this gene is needed to determine its exact role in the plant-nematode interactions, but the silencing of parasitism genes through HIGS seems to provide a promising method of resistance.

Root-Knot Nematodes: Insights Into Their Parasitism and Lipid Diet

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