Transcriptomic analysis and review of CDL-gated photoperiodic flowering mechanisms in C. sativa and their responsiveness to R:FR ratios in controlled environment agriculture

While single mechanisms have been identified, a comprehensive 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, pseudo-response-regulator 37 (PRR37) has been shown to have a causal effect in determining photoperiod sensitivity. This study identifies a network of WNK-kinases (WNK) which may be regulating the PRR genes and those downstream of it. 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. It is also likely to act as a repressor of FT, as its increased expression is associated with decreased expression of FT. Furthermore, we demonstrate the manipulation of gene expression through modified horticultural light wavelengths.