Genome-Wide Identification and Expression Analysis of CesA Gene Family in Corymbia citriodora

The CesA proteins are key players in cellulose synthesis. Eucalyptus is well-known for cellulose synthesis, although the mechanism of cellulose synthesis is largely unknown. In this study, 11 CcCesA genes were identified by comprehensive bioinformatics analysis in Corymbia citriodora, a eucalypt species. CcCesA genes were generally conserved in each subfamily. Among them, four genes lacked a transmembrane domain in the N-terminal. We showed that genes of CesA2, 4, 5, and 8 may regulate the synthesis of secondary cell walls (SCWs) through phylogenetic trees analysis. Two pairs of segmental duplication and one pair of tandem duplication were detected in CcCesAs. Analysis of Ka/Ks ratios revealed that the duplicated genes were under negative or purifying selection. Numerous cis-acting elements related to plant hormones and light reactions were identified in the promoters of CcCesAs. Expression analysis confirmed that genes of CesA2, 4, and 8 regulate the synthesis of SCWs, and CesA8, in particular, had the highest expression compared with other genes. The results will help us understand the complexity of the CcCesAs in different diameters at breast height and provide valuable information for future functional characterization of specific genes in C. citriodora.