Differential gene expression analysis reveals transcription factors that control flower initiation and development in Cannabis sativa

RNA-Seq and differential gene expression analysis were employed to identify transcription factors (TF) that are specifically expressed in developing buds, and potentially control flower timing and organ development in C. sativa. We found 199 TFs that were upregulated and 140 TFs that were downregulated in floral buds compared to young leaves. Of these, 16 exhibited strong homology to MADS Box type TFs that control flower timing and pattern development in other plants. For proof of concept, we assessed the in planta roles of two SEPALLATA-type TFs through the stable overexpression of these genes in Arabidopsis thaliana plants. Transgenic plants overexpressing csSEP3 grew at a slower rate compared to wild-type plants during the early growth stages, but they caught up to wild-type plants after 20 days of growth. On the other hand, transgenic plants overexpressing csSEP1 exhibited stunted growth, and produced floral buds about 10 days earlier than the wild-type controls. At the time of bolting, these plants had 8.5 ± 0.2 rosette leaves, while transgenic plants overexpressing csSEP3 and the wild-type plants had 31.8 ± 3.9 and 38.4 ± 2.9 leaves, respectively. Flower pattern development was not affected in either of the transgenic plants. Not surprisingly, production of the floral scent constituents (monoterpenes) was not affected in either transgenic plant. The differentially expressed genes (in particular TFs) highlighted in this study represent a valuable resource for further investigating the molecular basis of flower development in C. sativa.