Ready for battle: histone modifications shape rice intergenerational memory to protect against nematode attack

Accumulating scientific insights reveal the ecological and evolutionary implications of phenotypic plant plasticity in response to biotic and abiotic stress factors. This study confirms that root-knot nematode infection leads to intergenerational acquired resistance (IAR) in rice offspring. Genome-wide and targeted gene expression analyses demonstrated that offspring of nematode-infected rice plants are better prepared to fight against such attack through 'spring loading' of hormone-related plant defense genes. These genes are suppressed under basal conditions in IAR plants but show a more dramatic induction upon nematode attack. Here, ChIP-sequencing was executed on the offspring of IAR versus naive plants to investigate if histone modifications could be involved in the spring-loaded expression pattern. This revealed enrichment of H3K4me3 on defence related genes and H3K27me3 on development-related genes in roots of IAR plants. Detailed bio-informatic analyses pointed towards significant epigenetic changes to the ABA, ET and MAPK signalling pathways in the offspring of nematode-infected plants. A rice line with reduced activity for OsMPK5 was found to be deficient in defense spring loading and the IAR phenotype. Transmitting a memory of encountered stress factors to one's offspring is arguably an important asset for the adaptation of sessile plant communities to hostile environments.