Tea Polyphenols Biosynthesis And Genes Expression Control In Tea (Camellia Sinensis)

Great precision in rapid genetic improvement of crops (more targeted) requires clear understanding of the plant genomes before directing the improvement process. Therefore, understanding plant biological processes (pathways and pathway interactions) that determine productivity and/or quality is a prerequisite for effective and efficient plant improvement programs. Tea is an important crop whose consumption as a non-alcoholic beverage worldwide is unsurpassed by any other. Tea polyphenols generally referred to as catechins in this beverage have not only been largely associated with the sensory characteristics used for its commercial valuation but also health benefit. Quality is at the centre of most genetic improvement programs for this crop. However, genetic studies as in other perennial crops take a long time to accomplish due to the long reproductive cycle. Strategies aimed at generating tools for rapid genetic improvement of this crop are highly desirable to counter the emerging challenges to the crop and to address needs for development of novel products. The investigations under review were carried out to determine potential targets in the crop's biochemical synthetic pathway for genetic improvement of quality characteristics.In this report, the role of the tea polyphenols in plant protection was assessed. Using Arabidopsis, it was demonstrated that the tea polyphenols comprising mainly the catechins alleviate UV-B stress in plants. Tea polyphenols treated plants showed less damage over a 24 hour exposure to UV-B compared to the non-treated plants. The tea polyphenols suppressed expression of chalcone synthase; a basic enzyme in flavonoids synthesis pathway, in UV-B treated plants. Recovery from UV-B stress was enhanced in plants that were treated with tea polyphenols compared to control. From the results, it was inferred that tea polyphenols comprising of mainly the tea catechins are among the many plant components that are partially responsible for the mechanisms of protection of plants against UV-B.It was also observed those environmental factors; light and temperature play a significant role in expression of basic genes of the flavonoids synthesis pathway. Expression of phenylalanine ammonium lyase, chalcone synthase and dihydroflavonol 4-reductase genes is induced under low levels of white light. UV-B and white light showed synergistic expression of the basic genes than when either UV-B or white light was used. Within 15-30° C ranges, at least one chalcone synthase gene is expressed, however dihydroflavonol 4-reductase and phenylalanine ammonium lyase had optimum temperature conditions for expression. Expression patterns of basic genes in the tea polyphenols synthesis pathway were evaluated in leaves of tea at...