The role of flavonoids produced in response to cyst nematode infection of Arabidopsis thaliana

Flavonoids have diverse roles in plants, including defence against plant pathogens and regulation of local auxin transport. Flavonoids have been shown to be produced in feeding sites of root-knot nematodes induced in a leguminous plant, and it has previously been suggested that they may be responsible for manipulation of local auxin levels that underlie early feeding site development. Here we show that flavonoids are also produced in developing syncytia induced by Heterodera schachtii and in galls induced by Xiphinema diversicaudatum in a non-leguminous plant, Arabidopsis thaliana. We further investigated whether flavonoids are required for normal feeding site development by screening mutant lines of A. thaliana, defective in various parts of the flavonoid biosynthetic pathway, with H. schachtii. None of the lines showed a reduced capacity to support nematode infection and some showed a statistically significant increase in the numbers of female nematodes that developed. These data suggest that flavonoids are produced as part of the defence response to nematode infection rather than being an integral component of the mechanisms used by nematodes to induce feeding sites.