Enhancing virus-induced gene silencing efficiency in tea plants ( Camellia sinensis L.) and the functional analysis of CsPDS

Virus-induced gene silencing (VIGS) is an effective technology for gene functional analysis in tea plants, yet its efficiency needs enhancement, particularly in the Qiancha 1 (QC1) cultivar of Camellia sinensis. Employing pTRV1/pTRV2-CsPDS as a vector and leaf albinism rate as a silencing index, this study optimized the VIGS system by examining the effects of vacuum treatment duration, pressure, injection method, and cutting size on silencing efficiency. The results indicate that both injection and vacuum infiltration methods are viable in QC1, with the vacuum method exhibiting superior efficiency. The optimal vacuum infiltration conditions were determined to be 0.8 kPa for approximately 5 min. Phenotypic analysis showed that silencing the CsPDS gene resulted in leaves yellowing to varying degrees. Transcriptome analysis revealed disruptions in various pathways in these tea cuttings with differing levels of coloration, particularly in photosynthetic pigment biosynthesis and nitrogen metabolism. Interestingly, the content of theanine was higher in the cuttings with lower chlorophyll content. Analysis of differential gene expression profile and quantitative real-time PCR confirms that theanine accumulation is primarily due to increased synthesis and reduced degradation. These findings deepen our understanding of the metabolic and molecular mechanisms behind leaf coloration in tea plants.