Ma, Kaifeng

PHOTOSYNTHETIC RESPONSE TO GENOME METHYLATION MAY AFFECTS THE GROWTH OF CHINESE WHITE POPLAR

Genome methylation plays a key role in regulating gene expression but; however, there is limited knowledge exists concerning the link between DNA methylation and economic traits in forest trees. We measured photosynthetic characteristics and growth traits in 130 intraspecific hybrids of Chinese white poplar (Populus tomentosa Carr.) and detected their genomelevels of DNA methylation. The phenotypic data were normally distributed, and each trait had a significant difference among the hybrids. The netNet photosynthetic rate (Pn, 14.83　± 3.76 μmol m–2 s–1), stomatal conductance (Gs, 0.29　± 0.09 mol m–2　 s–1), and intercellular CO2 concentration (Ci, 264.50　± 30.94 μmol mol–1) showed similar trends. Positive correlations were found between Pn and height (H, 133.59　± 50.44 cm) and basal diameter (D, 16.29　± 5.20 mm), respectively. Using methylation-sensitive amplification polymorphism (MSAP) analysis, 32 primer-pair combinations generated 1,512 bands, 715 of which were polymorphic markers. Positive correlations between photosynthetic characteristics, such as Pn and Gs, and total relative methylation level and relative hemi-methylation (CNG relative methylation) relative level were investigated. Eighty -one candidate markers were associated with Pn, Gs, and/or Ci, 13 of which were also associated with growth traits using single MSAP molecular marker association. Sequencing and BLAST analysis showed that , selected from polymorphic markers using single MSAP molecular marker association, were associated with Pn, Gs, and/or Ci. Thirteen of these candidate markers were also associated with growth traits. candidate markers were linked to geness encoding protochlorophyllide reductase and proteins of cytochrome P450 CYP4/CYP19/CYP26 subfamilies, and linked to genes taking part in, e.g., photosystem II. Therefore, the regions defined by the these MSAP candidate markers are may linked to contain genes that are essential for photosynthetic characteristics that respond to DNA methylation and subsequently affect growth traits.

Keywords: Photosynthesis • DNA methylation • Growth trait • Methylation-sensitive amplification polymorphism (MSAP) • Candidate markers

Tree Genetics & Genomes, 1; Vol