Transcriptomic analysis of CDL-gated photoperiodic flowering mechanisms in cannabis and their responsiveness to R: FR...

While discrete regulatory mechanisms have been identified, a unified model for the transcriptional activation of photoperiodic flowering in short-day (SD) plants has not been delineated. Although the GIGANTEA-CONSTANS-FLOWERING LOCUS T (GI-CO-FT) pathway appears to be highly conserved, each species may differ in its blueprint for activation of FT and floral meristem identity. In cannabis, an SD plant, PSEUDO-RESPONSE-REGULATOR 37 (PRR37) has a causal effect in determining photoperiod sensitivity. This study identifies a network of WITH NO LYSINE (K) kinases (WNK) which may be regulating the PRR proteins and downstream genes, including florigen (FT). CO-like genes have been identified in cannabis, but their function in regulating FT has not been determined. This study shows that in cannabis, CO is critically-day-length-gated (CDL) and down-regulated by short days, likely to act as a repressor of FT. We demonstrate that CDL-gated gene expression can be manipulated in cannabis horticulture through modifying the R:FR ratio of LED lighting, where increased expression of COL5 in response to light treatment is inversely related with expression of FT. Building on these insights, we propose a model for the CDL-gated regulation of FT expression in cannabis.