Recently, the Tea tree genetics and breeding team at the Tea Research Institute of the Chinese Academy of Agricultural Sciences (CAAS) made significant progress in understanding the mechanism of tea plant induced resistance to the gray tea looper (Ectropis grisescens). The research paper titled “(+)-Catechin, epicatechin and epigallocatechin are important inducible defensive compounds against Ectropis grisescens in tea plants” was published in the prestigious international journal Plant, Cell & Environment (IF = 7.228).

To defend against herbivorous insect damage, plants have evolved a complex defense system that includes constitutive and induced resistance. By recognizing herbivorous insect-associated elicitors and damage patterns, plants activate multiple signaling pathways such as jasmonic acid (JA), salicylic acid (SA), ethylene (ET), auxin (IAA), gibberellin (GA), cytokinin (CK), and abscisic acid (ABA), and numerous transcription factors, leading to systemic insect resistance responses. Catechins are key flavor substances and functional components in tea leaves. Previous studies on catechins in tea plants have mainly focused on their biosynthesis, response to abiotic stresses, and regulating the content of catechins in tea plants through abiotic stresses such as low temperature and shading to improve tea quality. Some results have confirmed that catechins are important induced antimicrobial components in poplar. However, whether catechins are induced anti-insect substances in plants has not been reported.

Damage by gray tea looper larvae in the field

The researchers focused on this aspect and systematically studied the effects of feeding damage by gray tea looper larvae on subsequent larval growth and development, catechin component content, and various plant hormone contents. Based on the clear differences in catechin components that significantly reduce the growth and development rate of gray tea looper larvae, they further explored the regulatory roles of multiple plant hormone signaling pathways. The results showed that feeding by gray tea looper larvae induces a significant accumulation of (+)-catechin, epicatechin, and epigallocatechin gallate in tea plants, leading to direct defense reactions. This process is jointly regulated by JA, ET, and IAA signaling pathways. This study not only established a standardized method for simulating feeding by gray tea looper larvae but also greatly enhanced our understanding of the interaction between tea plants and gray tea loopers.

Effects of three different plant hormones on the weight of gray tea looper larvae and catechin content in leaves

This study was supported by the Science and Technology Innovation Program of the Chinese Academy of Agricultural Sciences and the National Natural Science Foundation of China. Assistant Researcher Li Xiwang and Assistant Researcher Zhang Jin were co-first authors of the paper, and Professor Sun Xiaoling from the Tea Research Institute of CAAS was the corresponding author.