Light-dependent green gall formation induced by Meloidogyne incognita

Meloidogyne incognita is one of the most detrimental root-knot nematode pests in the world because of its wide range of hosts, infecting almost all plant species. Following infection, this nematode induces gall formation in the root. We have found that these induced galls turn green in tomato roots exposed to light. This gall greening was light-dependent and inhibited by auxin treatment. Chlorophyll was detected in these green galls, and chloroplasts were also observed in the root-knot region. Expression of the chlorophyll a/b-binding protein-4 gene was upregulated in the galls. These results indicate that light treatment induces chloroplast development in tomato plants infected with M. incognita during gall development.