Understanding the biosyntheses and stress response mechanisms of aroma compounds in tea (Camellia sinensis) to safely and effectively improve tea aroma

Abstract

Metabolite formation is a biochemical and physiological feature of plants developed as an environmental response during the evolutionary process. These metabolites help defend plants against environmental stresses, but are also important quality components in crops. Utilizing the stress response to improve natural quality components in plants has attracted increasing research interest. Tea, which is processed by the tender shoots or leaves of tea plant (Camellia sinensis (L.) O. Kuntze), is the second most popular beverage worldwide after water. Aroma is an important factor affecting tea character and quality. The defense responses of tea leaves against various stresses during preharvest (tea growth process) and postharvest (tea manufacturing) processing can result in aroma formation. Herein, we summarize recent investigations into the biosyntheses of several characteristic aroma compounds prevalent in teas and derived from volatile fatty acid derivatives, terpenes, and phenylpropanoids/benzenoids. Several key aroma synthetic genes from tea leaves have been isolated, cloned, sequenced, and functionally characterized. Biotic stress (such as tea green leafhopper attack) and abiotic stress (such as light, temperature, and wounding) could enhance the expression of aroma synthetic genes, resulting in the abundant accumulation of characteristic aroma compounds in tea leaves. Understanding the specific relationships between characteristic aroma compounds and stresses is key to improving tea quality safely and effectively.

Keywords:

• Aroma
• biosynthesis; Camellia sinensis
• stress
• tea
• volatiles

Acknowledgements

This review is dedicated to the retirement memory of Prof. Dr. Naoharu Watanabe, whose pioneering research inspired several generations of tea researchers to pursue the study of tea aroma. We thank Dr. Jianlong Li at the Tea Research Institute, Guangdong Academy of Agricultural Sciences for kindly providing photos of tea green leafhoppers. Because of space limitations, we could not cite all publications in the field; we apologize to all colleagues whose work has not been mentioned.

Author contributions

Yang Z. constructed the manuscript outline. Zeng L. and Yang Z. wrote the manuscript. Yang Z., Zeng L., and Watanabe, N. contributed to the tea aroma-related research aspects done by the authors. All authors reviewed the manuscript.

Funding

A part of the research aspects done by the authors are supported by the financial supports from the National Natural Science Foundation of China (31670690, 31601787, and 31500244), the National Key Research and Development Program of China, the Guangdong Natural Science Foundation (2016A030313652, 2016A030306039, and 2014A030310131), the Guangdong Innovation Team of Modern Agricultural Industry Technology System (2017LM1143), and the Guangdong Special Support Plan for Training High-Level Talents (2016TQ03N617).