Identification of genes associated with sex expression and sex determination in hemp (Cannabis sativa L.).

Dioecy in flowering plants has evolved independently many different times, and thus the genetic mechanisms underlying sex determination are diverse. In hemp (Cannabis sativa), sex is controlled by a pair of sex chromosomes (XX for females and XY for males). In an attempt to understand the molecular mechanism responsible for sex expression in hemp plants, we carried out RNA-Seq of male and female plants at different developmental stages. Using a pipeline involving differential gene expression analysis and weighted gene co-expression network analysis, we identified genes important for male and female flower development. We also demonstrate that sex-biased expression is already established at very early vegetative stages, before the onset of reproductive development, and several genes encoding transcription factors of the REM, bZIP and MADS family as candidate sex determination genes in hemp. Our findings demonstrate that the gene regulatory networks governing male and female development in hemp diverge already at a very early stage, leading to profound morphological differences in male and female hemp plants.