Effects of stolbur phytoplasma infection on DNA methylation processes in tomato plants

Abstract

DNA methylation was investigated as a possible mechanism for regulation of floral gene expression in stolbur phytoplasma‐infected tomato buds. Expression of methylase and demethylase genes was found to be globally down‐regulated in tomato plants infected with stolbur isolate PO, but not in those infected with isolate C. These results are consistent with the finding that SlDEF, a gene orthologous to arabidopsis APETALA3 which is involved in petal formation, was down‐regulated in stolbur PO‐infected buds and remained unaffected in stolbur C‐infected buds, and with the fact that the two stolbur phytoplasma isolates C and PO induce distinct symptoms. Because of variations between the different cell‐types of the flower buds, the DNA methylation status of SlDEF could not be clearly established. However, the finding that treatment of stolbur PO‐infected plants with 5‐azacytidine partially restored SlDEF gene expression strongly suggests that DNA methylation is involved in down‐regulation of floral development genes in stolbur PO‐infected tomatoes.