Rice diterpenoid phytoalexins are involved in defence against parasitic nematodes and shape rhizosphere nematode communities

Abstract

Summary • Research and rationale: Rice diterpenoid phytoalexins (DPs) are secondary metabolites with a well-known role in resistance to foliar pathogens. Since DPs are also known to be produced and exuded by rice roots, we hypothesized that they might play an important role in plant-nematode interactions, and particularly in defense against phytoparasitic nematodes. • Methods: We used transcriptome analysis on rice roots to analyze the effect of infection by the root-knot nematode Meloidogyne graminicola or treatment with resistance-inducing chemical stimuli on DP biosynthesis genes, and assessed the susceptibility of mutant rice lines impaired in DP biosynthesis to M. graminicola. Moreover, we grew these mutants and their wild type in field soil and used metabarcoding to assess the effect of impairment in DP biosynthesis on rhizosphere and root nematode communities. • Key results: We show that M. graminicola suppresses DP biosynthesis genes early in its invasion process, and conversely that resistance-inducing stimuli transiently induce the biosynthesis of DPs. Moreover, we show that loss of DPs increases susceptibility to M. graminicola. Metabarcoding on wild-type and DP-deficient plants grown in field soil reveals that DPs significantly alter the composition of rhizosphere and root nematode communities • Main conclusions: DPs are important players in basal and inducible defense against nematode pathogens of rice and help shape rice-associated nematode communities.