Glutathione Promotes Susceptibility to Meloidogyne incognita by Modulating Thiol Homeostasis in Arabidopsis

Glutathione (l-γ-glutamyl-l-cysteinyl-glycine) is a key molecule that regulates numerous plant processes under both biotic and abiotic stress conditions. However, its role in plant responses to soilborne pathogens, particularly the economically important root-knot nematodes (Meloidogyne spp.), remains largely unexplored. Here, we investigated the role of glutathione in Arabidopsis thaliana during M. incognita infection using a combination of genetic (glutathione biosynthetic mutants), biochemical (thiol and camalexin measurements), and pharmacological (exogenous glutathione supplementation) approaches. We found that glutathione depletion in the roots of mutants in glutathione synthesis (rax1, pad2, cad2, and nrc2) significantly reduced gall formation by up to 27% and egg mass production by up to 33% compared with the control, suggesting its important role in nematode infection. Additionally, the exogenous application of glutathione increased plant susceptibility to M. incognita, resulting in a 23% increase in gall formation and a 19% increase in egg mass production compared with the mock-treated control. Biochemical analysis revealed that reduced glutathione levels disrupted the cysteine-glutathione balance early in the infection process. However, further assays, including camalexin measurements and infection assays with gstf6 loss-of-function lines, indicated that glutathione-dependent phytoalexin camalexin does not significantly contribute to M. incognita parasitism. These findings underscore the importance of glutathione in maintaining thiol homeostasis during the early stages of M. incognita infection and suggest that manipulating glutathione levels could be a potential strategy for nematode control in agriculture.