Ascorbate oxidation primes the rice plants for enhanced defence against root-knot nematode Meloidogyne graminicola through jasmonate/ethylene activation

Ascorbic acid (AA) is known to play a vital role in plant growth and detoxification of reactive oxygen species, however little is known about the significance of AA oxidation in plant defence against pathogens. The role of ascorbate oxidation in rice defence against root-knot nematodes, Meloidogyne graminicola, was tested with application of AA, ascorbate oxidase (AO), dehydroascorbic acid (DHA), biosynthesis inhibitors and use of mutants. Transcriptome analysis was done on AO treated plants, and hormone measurements were executed to confirm the results. Biochemical analyses were used to study oxidative stress markers, including accumulation of hydrogen peroxide (H2O2), malondialdehyde (MDA) and AA/DHA. AO and DHA treated plants are significantly less susceptible to M. graminicola, while AA mutants are significantly more susceptible. Transcriptome data, corroborated by hormone measurements, show that ethylene (ET) and jasmonic acid (JA), are activated in rice roots upon ascorbate oxidation, while Methyl-JA, ethephon or AO can complement the susceptibility phenotype of the vitamin C (vtc)mutant. Additionally, oxidative stress markers are accumulating in nematode-induced root galls. Our data further demonstrate a novel pathway showing that induced defence by ascorbate oxidation is dependent on a functional JA and ET pathway and leads to primed accumulation of H2O2.

Jaar van publicatie:2019

Toegankelijkheid:Open