Reduction of phytate by down-regulation of Arabidopsis thaliana MIPS and IPK1 genes alters susceptibility to beet cyst nematodes

Abstract

Phytates are mixed cationic salts of phytic acid formed by sequential phosphorylation of myo-inositol. Phytate is a phosphorus storage molecule essential for cellular and hormonal signalling in plants but exhibits anti-nutrient properties in animals. Low phytate plants have reduced basal resistance towards microbial pathogens and reduced tolerance to environmental stresses resulting in compromised yields. We report that three mutant lines of Arabidopsis thaliana, each with altered expression of myo-inositol-3-phosphate synthase (MIPS) isoforms, show altered susceptibility towards infection by the beet cyst nematode, Heterodera schachtii. Disruption of MIPS2 accompanied by increased MIPS1 expression results in reduced cyst nematode infection. Lack of MIPS3 resulted in a higher proportion of second-stage juveniles in the early phase of infection, suggesting delayed nematode development on mips3 mutants. Reduction in total phytate by down-regulation of the inositol polyphosphate kinase gene (IPK1) resulted in higher susceptibility to cyst nematode infection but a reduced average size of adult females. However, specific down-regulation of MIPS gene expression reduces susceptibility as myo-inositol is required to feed into the myo-inositol oxygenase pathway, which has an important role in development of the cyst nematode feeding site.