Comparative transcriptome analysis to reveal putative genes responsible for high theacrine content in Kucha (Camellia kucha (Chang et Wang) Chang)

Abstract Background: The purine alkaloid theacrine, synthesized in a high amount in Kucha (Camellia kucha (Chang et Wang) Chang), has shown multiple pharmacological effects such as anti-depression, dehydration and hypnotic activities. It is critical to better understand the theacrine metabolism at the molecular level for future breeding programs. Results: In this study, we carried out comparative transcriptome analysis of Kucha (Kucha-6 and Kucha-11) and conventional varieties (Yinghong 9 and Qingxin 1). HPLC showed that Kucha synthesized more than 27-fold theacrine in comparison to conventional varieties. A total of ~ 671.61 million high quality clean reads were yield, and 71.42 ~ 76.87% of these were aligned to the reference genome for each library. Among the 19,095 differentially expressed genes (DEGs) identified by a pairwise comparison approach, a pool of 1,142 common DEGs between Kucha and conventional varieties were screened. Functional annotation allowed the identified of 20 oxidoreductase (OR) genes and seven methyltransferase (MT) genes with enhanced expression in Kucha, which might be associated with theacrine diversity in the examined materials. Particularly, two N-methyltransferase-encoding genes (TEA010054 and TEA022559) may catalyze the final methylation step during theacrine synthesis in Kucha. Conclusion: The current study focused on screening genes of theacrine formation in tea plant, which contributes to the elucidation of candidate genes and breeding tea plant with high theacrine content.