RNA-Seq analysis of gynoecious and weak female cucumber revealing the cell cycle pathway may regulate sex determination in cucumber

Abstract

This study aims to investigate key genes involved in molecular regulatory networks of cucumber sex determination. Genome-wide high-throughput RNA sequencing was performed for young apical buds of gynoecious and weak female cucumber at three growth stages (one-leaf one-bud, three-leaf one-bud, and five-leaf one-bud). Seven comparisons from the same cultivar at three different stages and at the same stage between the two cultivars were analyzed, and the results revealed that compared with differentially expressed genes (DEGs) in weak female cucumber, more genes were upregulated at the one-leaf one-bud stage and downregulated at the three-leaf one-bud stage in gynoecious cucumber. In addition, there were four kinds of gene expression trends (0, 1, 6, and 7), which were significantly enriched in gynoecious cucumber, while only two kinds of gene expression trends (5 and 6) were significantly enriched in weak female cucumber. Together with the data of the Gene Ontology (GO), pathway, gene expression trends and qRT-PCR, nine genes were identified and considered as candidate genes that may be involved in sex differentiation regulation in cucumber. These genes included Cs-MCM6, Cs-ACT3, Cs-XRCC4, Cs-MCM2, Cs-CDC45, Cs-Dpri, Cs-H2B, Cs-CDC20 and Cs-CNGC1. Among these genes, five genes (Cs-MCM6, Cs-MCM2, Cs-CDC45, Cs-Dpri, and Cs-CDC20) were involved in the cell cycle pathway, suggesting that the cell cycle pathway may play an important role in sex determination in cucumber.