MYC2 influences rubber and sesquiterpene lactones synthesis in Taraxacum species

Main conclusion: This study showed that MYC2 transcriptionally regulates valuable metabolites in Taraxacum spp. through direct interaction with specific target gene promoters. Abstract: The Russian dandelion (Taraxacum kok-saghyz) represents a promising alternative species, capable of producing several high-added-value compounds, including natural rubber. Nevertheless, further enhancements are required for its optimal utilization by the industry. Here, we explored the role of the bHLH transcription factor TksMYC2, homolog of AtMYC2, in the regulation of the biosynthesis of specialized metabolites and free fatty acids and in the control of natural rubber production. Metabolic analyses of Taraxacum kok-saghyz plants showed that the overexpression of TksMYC2 significantly affected the accumulation of metabolites in roots and leaves, such as sesquiterpene lactones, phenylpropanoids, and free fatty acids. Moreover, overexpressing plants presented a significant increase in natural rubber production in both Taraxacum kok-saghyz and its related species Taraxacum brevicorniculatum. The direct interaction of TksMYC2 with the regulatory regions of cis-prenyltransferase 2 (CPT2), small rubber particle proteins (SRPP1, SRPP3, and SRPP4), involved in the biosynthesis of natural rubber, and with the germacrene A oxidase (GAO), involved in the biosynthesis of sesquiterpenes, was demonstrated by chromatin immunoprecipitation coupled with quantitative PCR. Additionally, these genes were highly induced in the lines overexpressing TksMYC2. Our findings suggest that TksMYC2 and its downstream components may be valid targets for breeding programmes to increase the production of valuable metabolites, including natural rubber.