Transcriptome profiling of differentially expressed genes of male and female inflorescences in spinach (Spinacia oleracea L.).

Spinach (Spinacia oleracea L.) is commonly considered a dioecious plant with heterogametic (XY) and homogametic (XX) sex chromosomes. The characteristic is also utilized for the production of spinach hybrid seeds. However, the molecular mechanisms of sex determination in spinach are still unclear because of a lack of genomic and transcriptomic information. In this study, RNA sequencing (RNA-seq) was performed in male and female inflorescences to provide insight into the molecular basis of sex determination in spinach. Comparative transcriptome analyses showed that 2278 differentially expressed genes (DEGs) were identified between male and female inflorescences. A high correlation between the RNA-Seq and qRT-PCR validation for DEGs was observed. Among these, 182 DEGs were annotated to transcription factors including the MYB family protein, bHLH family, and MADS family, suggesting these factors might play a vital role in sex determination. Moreover, 26 DEGs related to flower development, including nine ABCE class genes, were detected. Expression analyses of hormone pathways showed that brassinosteroids may be key hormones related to sex determination in spinach. Overall, this study provides a large amount of DEGs related to sexual expression and lays a foundation for unraveling the regulatory mechanism of sex determination in spinach.