Knocking down a DNA demethylase gene affects potato plant defense against a specialist insect herbivore.

DNA demethylase (DML) is involved in plant development and responses to biotic and abiotic stresses, however, its role in plant-herbivore interaction remains elusive. Here, we found that the potato tuber moth, Phthorimaea operculella's herbivory rapidly induced the genome-wide DNA methylation and accumulation of DML genes' transcripts in potato plants. Herbivory-induction of DMLs' transcripts was suppressed in jasmonate-deficient plants, whereas exogenous application of methyl jasmonate (MeJA) improved DMLs' transcripts, indicating that the induction of DMLs' transcripts by herbivory is associated with jasmonate signaling. Moreover, P. operculella larvae grew heavier on a DML gene (StDML2)-knocked-down plants than on wildtype plants, and the decreased biosynthesis of jasmonates in the former may be responsible for this difference, since the larvae feeding on these two genotypes supplemented with MeJA showed similar growth. In addition, P. operculella adult moth preferred to oviposit on StDML2-knocked-down plants than on wildtype plants, which was associated with the reduced emission of ß-caryophyllene in the former. And supplementing ß-caryophyllene to these two genotypes further disrupted moths' oviposit choice preference for them. Interestingly, in StDML2-knocked-down plants, hypermethylation was found at the promoter regions for the key genes StAOS and StAOC in jasmonate biosynthetic pathway, as well as for the key gene StTPS12 in ß-caryophyllene production. Our findings suggest that knocking down StDML2 can affect plant's herbivore defense via affecting jasmonate signaling and defense compound production in potato plants.