Identification and expression analysis based on RNA-Seq of the pectin methylesterase gene family in Ziziphus jujuba

  Objective  Pectin is a major component and structural polysaccharide of the cell walls of plants. Pectin methylesterase (PME) is a key enzyme that modifies pectin, and thereby regulates cell wall rigidity and elasticity, playing a significant role in the plant development. The purpose of this study was to investigate the basic information and characteristics of ZjPMEs, which could serve as a foundation for further elucidation of the functions of ZjPME genes and screening of genes closely related to fruit texture.

  Method  We identified the family genes in the ‘Dongzao’ genome using bioinformatics softwares.The characteristics and expression patterns of the genes were analyzed based on RNA-seq data.

  Result  46 PME genes were identified in the jujube genome, including 29 Type- ⅠZjPMEs and 17 Type-ⅡZjPMEs, which were classified into four subfamilies (Ⅰ −Ⅳ) and unevenly distributed across 10 chromosomes. Within each subfamily, the genes shared conserved gene structure and motif compositions. Expression analysis revealed that most of the genes were expressed highly in flowers, indicating the important function of PME genes in the reproductive developmental process. Furthermore, by analyzing the expression patterns of the ZjPMEs during the fruit development between ‘Dongzao’ (crisp) and ‘P15’ (firm), and between ‘Dongzao’ (consumed freshly) and ‘Junzao’ (consumed as dry fruit), we found ZjPME18 might be closely related to fruit texture. ZjPME18 showed higher expression in ‘Junzao’ and ‘P15’.

  Conclusion  The ZjPMEs have specific structure characteristics and expression patterns, and the expression and regulation of ZjPME18 may be closely related to the fruit texture.