A Smoky Genome
Despite progress in genome sequencing and genome assembly, cannabis lacks a high-quality reference genome. In addition, inconsistencies in the publicly available genomes creates an unique challenge for comparative analysis.
Here, at TAGC, we are working on developing a high-quality synthetic reference genome with a minimal gaps.
Sex Matter
Cannabis is an annual dioecious species with separate male (XY) and female (XX) plants. In cannabis, sexual dimorphism occurs in a late stage of plant development (i.e., flowering) accompanied by a morphological dimorphism. In general, females produce compact and rarely lax inflorescence with flowers on the main shoot and short lateral branches, while males produce an inflorescence in the form of loose terminal and axillary panicles. It is considered that cannabis has one of the most complicated mechanisms of sex determination and sex inheritance among dioecious plants. While the genetic determinism of sex in cannabis is considered an important heritable trait for genetic improvement, its sexuality is not well known, is plastic and can be changed. In addition to environmental factors, application of exogenous plant growth regulators or inhibitors can modify or reverse sex morphology in cannabis.
To date, different types of monoecious, dioecious, and hermaphrodite varieties have been reported in cannabis. In general, unfertilized female plants are preferred for cannabinoid production (e.g., THC, CBD) as their inflorescences are significantly richer in cannabinoid content and monoecious plants for seed and fiber production. Different genetic models have been proposed to explain sex determination in cannabis, but cannabis sex can be altered during development to express the opposite sex without changing their genotype.
Here, at TAGC, we think that epigenetic mechanisms are most likely implicated in mediating sex expression and sex change in cannabis, as the sex is not determined by particular chromosomes, but by the whole genome, and by the gene and chromosome interactions. Thus, all individuals are able to express one or the other sex. As a result, the fundamental question arising here is “how genetic and epigenetic factors interact and regulate sex expression in cannabis?” Therefore, here we are trying to understand the biology of sex in cannabis and its application for genetic improvement.