From dawn ‘til dusk: daytime progression regulates primary and secondary metabolism in Cannabis glandular trichomes

Cannabis sativa L. glandular trichomes (GTs) synthesise large amounts of specialised secondary metabolites, predominantly cannabinoids and terpenoids. The associated demand for carbon and energy makes GTs strong sink tissues and there is indication that their secondary metabolism is coupled to the availability of photoassimilates. Many metabolites, including secondary metabolites, show diurnal patterns of flux but it is unknown whether cannabinoids and terpenoids are regulated by time of day. We quantified cannabinoids, terpenoids and the GT proteome over a 12-hour light period in flowers of Hindu Kush, a high-tetrahydrocannabinol (THC) cultivar. Major cannabinoids showed significant changes over the course of day, resulting in an increase in total measured cannabinoids. Major terpenoids also showed changes, with sesquiterpenes generally decreasing with day progression. While monoterpenes generally did not decrease, the second most abundant, a-pinene, increased. The GT proteome changed the most within the first six hours of the day and analysis of differentially abundant proteins indicated upregulation of primary metabolism. Surprisingly, key cannabinoid biosynthetic enzymes decreased with daytime progression despite increases in cannabinoid content, which might indicate that daytime increases of photoassimilates are the main driver of cannabinoid regulation. This first reporting of variability of cannabinoid and terpenoid biosynthesis over the course of the day has implications for Cannabis research and production.

大麻（Cannabis sativa L.）的腺毛（glandular trichomes, GTs）可合成大量特化次生代谢产物，主要成分为大麻素与萜类化合物。此类代谢过程所需的大量碳源与能量，使得腺毛成为强库组织；同时有研究表明，其次生代谢与光合产物的可获得性紧密关联。诸多代谢产物（含次生代谢产物）均表现出昼夜波动模式，但目前尚不明确大麻素与萜类化合物的合成是否受昼夜时段调控。本研究针对高四氢大麻酚（THC）品种兴都库什（Hindu Kush）的花组织，在12小时光照周期内对大麻素、萜类化合物及腺毛蛋白质组进行了定量分析。结果显示，主要大麻素类物质在日间呈现显著变化，最终导致总检测大麻素含量升高；主要萜类化合物同样存在动态变化，其中倍半萜类物质随日间推进整体呈下降趋势。单萜类物质整体未出现下降，但丰度排名第二的α-蒎烯含量有所升高。腺毛蛋白质组在日间前6小时内变化最为剧烈，差异丰度蛋白分析结果表明初级代谢通路被上调激活。令人意外的是，尽管大麻素含量随日间升高，但关键大麻素生物合成酶的表达量却随日间推进而下降，这一现象或提示光合产物的日间累积是大麻素调控的主要驱动因素。本研究首次报道了大麻素与萜类化合物生物合成的日间动态变化，该发现对大麻研究与产业生产均具有重要参考价值。