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

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.

P1 of strawberry vein banding virus, a multilocalized protein, functions as a movement protein and interacts with the coat protein

Although the complete nucleotide sequence of strawberry vein banding virus(SVBV) has been determined and bioinformatic analysis has revealed that the SVBV genome could encode seven proteins, the precise function of each protein is unclear. This study provided evidence that the P1 protein of SVBV(SVBV-P1) possesses the following features. Bioinformatic and subcellular localization analyses showed that SVBV-P1 is localized in the cytoplasm and cell walls of epidermal cells in Nicotiana benthamiana, and it forms inclusion bodies associated with microtubules and the endoplasmic reticulum. Dilution experiments demonstrated that SVBV-P1 could move from the original agro-infiltrated cells to adjacent cells in N. benthamiana leaves. Further trans-complementation experiments demonstrated that SVBV-P1 could facilitate the intercellular movement of a movement-deficient potato virus X mutant in N. benthamiana leaves. Finally, yeast twohybrid and bimolecular fluorescence complementation assays revealed that SVBV-P1 could interact with the SVBV coat protein, which is a major component of Caulimovirus virions. Results of the electrophoretic mobility shift assay indicated that SVBV-P1 lacks DNA-binding capability. In summary, the results suggest that SVBV-P1 is probably a movement protein of SVBV, providing new insights into the function of movement proteins of the Caulimovirus genus.

Complete genome sequence of two strawberry vein banding virus isolates from China

It was rarely reported about strawberry vein banding virus(SVBV)genome sequence in China and most countries worldwide.In this work,we determined the complete genome sequences of two SVBV isolates in China,designated SVBV-AH and SVBV-BJ,that were obtained from naturally infected strawberry samples from Anhui province and Beijing city of China,respectively.The complete genomes of SVBV-AH and SVBV-BJ were 7,862 nucleotides(nts)and 7,863 nts long,respectively,and both constituted with seven genes typical of the caulimoviruses.Alignment of complete nucleotide sequences showed that SVBV-AH and SVBV-BJ shared a significant nucleotide sequence identity of 97.7%of each other and had 85.7%and 86.0%sequence identity related to SVBV from the United States(SVBV-US),respectively.Phylogenetic trees,based on the alignment of complete nucleotide sequences and amino acid sequences of Coat Protein(CP),both showed that SVBV-AH and SVBV-BJ clustered into one branch with all the other SVBV isolates,and other species of caulimoviruses clustered into another tree branch.It illustrated that all the SVBV isolates had an extremely high relationship but had a distant relationship with other species of caulimoviruses.We further confirmed that SVBV-AH infectious clone could cause similar symptoms to SVBVinfected in strawberry under natural conditions.Taken together,our study provided valuable information to elucidate the origin and dissemination of SVBV Chinese isolates,meanwhile providing the necessary vector for studying the gene functions of strawberry.