Isolation and characterization of a maintenance DNA-methyltransferase gene from peach (Prunus persica [L.] Batsch): transcript localization in vegetative and reproductive meristems of triple buds

A cDNA coding for a DNA (cytosine-5)-methyltransferase(METase) was isolated from peach (Prunuspersica [L.] Batsch) and the corresponding genedesignated as PpMETI. The latter encoded a predictedpolypeptide of 1564 amino acid residues andharboured all the functional domains conserved inthe maintenance METases group type I. PpMETI wasa single copy in the cultivar Chiripa which was usedas a model in the present study. Expression analysesrevealed that PpMETI transcripts were more abundantin tissues with actively proliferating cells such as apicaltips, uncurled leaves, elongating herbaceousstems, and small immature fruits. Peach plants bearbud clusters (triads or triple buds), consisting of twolateral and one central bud with ¯oral and vegetativefates, respectively. PpMETI in situ hybridization wasperformed in triple buds during their entire developmentalcycle. High and low levels of PpMETI transcriptwere related to burst and quiescence ofvegetative growth, respectively. Message localizationdistinguished lateral from central buds during themeristem switch to the ¯oral phase. In fact, thePpMETI message was abundant in the L1 layer ofprotruding domes, a morphological trait marking thebeginning of ¯oral transition. The PpMETI transcriptwas also monitored during organ ¯ower formation.Altogether, these data suggest a relationshipbetween DNA replication and PpMETI gene expression.