Purine alkaloids in tea plants: component, biosynthetic mechanism and genetic variation

The purine alkaloids, including caffeine, theobromine, and theacrine, are one of the most important quality and functional components of tea plants and commercial teas. In this paper, we review the component, biosynthetic mechanism and genetic variation of purine alkaloids in tea plants. The content of caffeine and theobromine in 403 accessions Chinese tea germplasms core collection preserved in the National Germplasm Hangzhou Tea Repository were analyzed using High Performance Liquid Chromatography (HPLC). The purine alkaloid profiles of different tea varieties, germplasm types, geographical origin, seasons, were highlighted. Some naturally low caffeine or caffeine-free, high theobromine or high theacrine germplasms were identified and the possible biosynthetic mechanism of hypernormal purine alkaloid content in tea plants were partially revealed. Some Cleaved Amplified Polymorphic Sequences (CAPS) DNA markers were developed for the identification of purine alkaloid content. The potential application of genetic engineering and DNA markers developed based on the low caffeine TCS1 (tea caffeine synthesis gene) alleles for marker assisted selection (MAS), and cocoa tea and kucha in low caffeine/high theacrine tea cultivar breeding programs were also reviewed.