UV photomorphogenesis : gene expression in cannabis in response to UV exposure : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Horticultural Science at Massey University, Manawatū, New Zealand
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2022
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Massey University
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Globally, changes in legislation have led to a significant increase in large scale commercial cultivation of Cannabis sativa (cannabis). For commercial growers, both yield and the concentration of cannabinoids in the harvested flower are key metrics for determining the value of a crop. In cannabis, the concentration of cannabinoids is determined both by underlying cultivar genetics and environmental factors. Ultraviolet (UV) radiation is already known to impact the growth and development of crop plants and has shown potential for use in beneficially controlling agronomically desirable outcomes, including improved disease resistance, increased yields, and greater accumulation of flavonoids in a range of crops. There are few historical studies on the impact of UV light on cannabis, however, preliminary research from BioLumic Limited – a New Zealand biotechnology company, has shown that short duration UV light treatments of young plants could be used to increase the yield and the content of commercially valuable cannabinoids THC and CBD. Little is known about the underlying molecular-level responses of cannabis to UV and extending this knowledge may reveal gene expression diagnostic targets that could be used in increasing the speed and impact of commercial UV light treatment development. In this study, a series of trials were carried out, where young cannabis clonal plants from a range of cannabis genetics were exposed to a number of proprietary UV light treatments. Plants were removed on a timeseries throughout the UV treatment regimens and were assayed via RT-qPCR to provide a timeseries of the expression of genes known to be involved in either UV signalling response, or cannabinoid biosynthesis. UV treatment induced several significant timepoint-based changes in relative expression of UV-response genes CHS and HY5, but induced limited expression-based change in the cannabinoid biosynthesis genes CBDAS and THCAS. Study results also indicated that plants displaying (pre-UV treatment) stress symptoms may be primed to respond more strongly to UV treatments, as indicated by higher levels of initial CHS gene expression. This study also showed that clone plants originating from different mother plants from the same variety (or 'strain') of cannabis, exhibited differences in gene expression when exposed to the same UV treatment. Future work will further explore the response of cannabis to UV treatments, including the expression of genes that may be used as markers for increasing the speed of commercially valuable UV treatment development.
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Figures 1.2 (=Yin & Ulm, 2017 Fig 2) and 1.3 (=Jenkins, 2017 Fig 1) have been removed for copyright reasons.