Cannabinoids are synthesized in glandular stalked trichomes on the female flowers of Cannabis sativa (cannabis). The regulation of glandular trichome development has not been characterized in cannabis. We recently identified an R2R3-MYB transcription factor, CsMIXTA, which could be involved in trichome morphogenesis in cannabis. Some homologous genes of CsMIXTA are known to function in glandular trichome initiation in other plant species. CsMIXTA is highly expressed in flower tissue compared to vegetative tissues. Interestingly, CsMIXTA is also highly expressed in trichomes isolated from female flower tissue. In addition, CsMIXTA is upregulated during the peak stages of female flower maturation in correlation with some cannabinoid biosynthetic genes. Transient expression in Nicotiana benthamiana showed that CsMIXTA is localized in the nucleus. Furthermore, yeast transcriptional activation assay demonstrated that CsMIXTA has transactivation activity. Overexpression of CsMIXTA in Nicotiana tabacum resulted in higher trichome density, larger trichome size, and more branching on stalked glandular trichomes. The results indicate that CsMIXTA not only promotes glandular trichome initiation in epidermal cells, but also regulates trichome development in tobacco leaves. In this report, we characterized the novel function of the first cannabis transcription factor that may be critical for glandular trichome morphogenesis.

Cannabis is a short day (SD) plant whose inflorescences produce valuable medicines. By studying the mechanisms of photoperiodic flowering initiation in cannabis, we may develop new methods of improving cultivation. In SD plants, CONSTANS, which is enhanced by CDL gated proteins that are expressed during short days, acts as a bifunctional regulator of flower inhibition or genesis via FT (florigen). These genes are downstream of phytochrome, which may be activated by horticultural lighting conditions like red (R, 660nm) to far red (FR, 700+nm) wavelength ratios. This study demonstrates that gene expression can be manipulated using high and low R:FR ratios, and characterizes the expression levels of CONSTANS, FT, PRR37, and SOC1 in cannabis over the first 14 short days. It also demonstrates the resulting effect on cannabinoid production and biomass yields.