Identification and Expression Analysis of D-type Cyclin Genes in Early Developing Fruit of Cucumber (Cucumis sativus L.)

Plant D-type cyclin genes (CYCDs) are important regulators of cell division. However, little is known on their participation during the early developmental stage of cucumber fruit. In this study, cucumber CYCD genes were identified and characterized. The expression levels of these genes during early fruit development were assessed from 0 to 8 days after anthesis (DAA). The results revealed the presence of 13 different CYCD genes, which were named according to identity percentages of the corresponding orthologs in Arabidopsis thaliana and poplar. The genomic organization of each subgroup CYCD was similar to their orthologs in A. thaliana and poplar. The expression levels of CsCYCD genes were analyzed in cucumber fruits under different treatments including natural parthenocarpic fruit, pollinated fruit, and N-(2-chloro-4-pyidyl)-N′-phenyurea (CPPU)-induced parthenocarpic fruit. The highest expression levels of most CsCYCDs genes were at four DAA in natural parthenocarpic and pollinated fruits. Interestingly, the expression patterns of 8 of 13 CsCYCD genes in natural parthenocarpic fruit were similar to those in pollinated fruit, but different from those in CPPU-induced parthenocarpic fruit. Collectively, the results of this study provide insights on the CYCDs involved in cucumber parthenocarpic fruit development.