Stolbur phytoplasma-infected tomato showed alteration of SlDEF methylation status and deregulation of methyltransferase genes expression

Phytoplasmas are phloem-restricted plant pathogenic bacteria belonging to the class Mollicutes. In stolbur phytoplasma-infected tomato, flower abnormalities have been associated with changes in the expression of floral development genes. In particular, FALSIFLORA (FA) is up-regulated whereas SIDEFICIENS (SIDEF) is down-regulated. To determine whether methylation is involved in down-regulation of SIDEF, the effect of phytoplasma infection on CpG methylation status of SIDEF was studied, MSRE-PCR and bisulfite sequencing showed that SIDEF was hypermethylated in tomato infected with the stolbur strain PO. The chromomethyltransferase genes studied by RT-PCR were down-regulated. Moreover, PO-tomato treated with 5-Azacytidine showed flowers and fruits, suggesting that SIDEF was no more deregulated. These results suggest that the stolbur phytoplasma could be involved in the inhibition of the demethylation of SIDEF.