Cytosine methylation at CG and CNG sites is differential during the development of triploid black poplar

Abstract

It has been widely shown that polyploidization can result in changes in cytosine methylation. However, little is known regarding how cytosine methylation changes in polyploids development, especially in polyploid trees. In this study, we investigated drifting changes of DNA methylation status at 5′-CCGG sites in the apical bud, young and mature leaf tissues of triploid black poplar (Populus. euramericana) with methylation-sensitive amplification polymorphism (MSAP) and assessed the expression of multiple DNA methyltransferases (MTases) and DNA demethylase during different developmental stages. MSAP analysis detected methylation levels at CG and CNG sites of diploid tissues reduced during development from bud to leaves, while for the triploid, methylation at CNG sites increased during development, but levels of methylation at CG sites first decreased in young leaves before increasing in mature leaves. MTase genes related to CG or CNG methylation were respectively preferential in different triploid tissues with high CG or CNG methylation levels. High expression of DNA demethylase was observed in tissue with high demethylation trends. These finding suggest CG and CNG methylation and their related enzymes are involved with different biological functions and networks of gene regulation in different developmental stages of triploid.