Phosphate deficiency induced by infection promotes synthesis of anthracnose-resistant anthocyanin-3-O-galactoside phytoalexins in the Camellia sinensis plant

Abstract

Abstract Tea (Camellia sinensis) is a well-known beverage crop rich in polyphenols with health benefits for humans. Understanding how tea polyphenols participate in plant resistance is beneficial to breeding resistant varieties and uncovering the resistance mechanisms. Here, we report that a Colletotrichum infection-induced ‘pink ring’ symptom appeared outside the lesion, which is highly likely to occur in resistant cultivars. By identifying morphological feature-specific metabolites in the pink ring and their association with disease resistance, and analysis of the association between metabolite and gene expression, the study revealed that the accumulation of anthocyanin-3-O-galactosides, red phytotoxin compounds resistant to anthracnose, plays a pivotal role in the hypersensitive response surrounding infection sites in tea plants. The results of genetic manipulation showed that the expression of CsF3Ha, CsANSa, CsUGT78A15, CsUGT75L43, and CsMYB113, which are involved in anthocyanin biosynthesis, is positively correlated with anthracnose-resistance and the formation of the pink ring. Further phosphorus quantification and fertilization experiments confirmed that phosphate deficiency caused by anthracnose is involved in the occurrence of the pink ring. Genetic manipulation studies indicated that altering the expression levels of Pi transporter proteins (CsPHT2-1, CsPHT4;4) and phosphate deprivation response transcription factors (CsWRKY75-1, CsWRKY75-2, CsMYB62-1) enhances resistance to anthracnose and the formation of the pink ring symptom in tea plants. This article provides the first evidence that anthocyanin-3-O-galactosides are the anthracnose-resistant phytoalexins among various polyphenols in tea plants, and this presents an approach for identifying resistance genes in tea plants, where genetic transformation is challenging.