A single gene may shape the taste of tea

Tea (Camellia sinensis) is one of the most widely consumed beverages in the world, and the size of the young buds directly affects both yield and quality. Larger buds can increase leaf mass, while different teas require specific bud to leaf ratios to meet processing standards. However, the genetic regulators that control bud size remain poorly understood, limiting breeding progress.

Previous studies indicate that shoot development is dependent on networks of transcription factors, including KNOX regulatory pathways, but their functions in tea are not fully understood. Due to these problems, in-depth research is needed to identify the key genes regulating tea bud size.

Researchers from the Tea Research Institute of the Chinese Academy of Agricultural Sciences conducted a comprehensive study using digital phenotyping, genome-wide association analysis and comparative transcriptomics. The conclusions were published February 20, 2025, at Horticulture Research. The team studied 280 different tea samples and identified the class I KNOX gene, CsKNOX6, as a major negative regulator of bud size. Overexpression of CsKNOX6 in Arabidopsis thaliana significantly reduced leaf area, supporting its role in limiting organ growth.

Using image-based phenotyping, the researchers quantified the length, width, perimeter and area of ​​buds from 280 tea germplasm samples. These traits showed continuous variation and high heritability, indicating strong genetic control. Comparative transcriptomic analysis of samples with extreme kidney size identified four class I KNOX candidates. transcription factors with significantly higher expression in varieties with small buds.

Among them, genome-wide association mapping identified CsKNOX6 as the most likely key regulatory gene. CsKNOX6 is located on chromosome 10, and its sequence suggests a nuclear localization consistent with transcriptional regulatory activity.

To confirm its function, the team overexpressed CsKNOX6 in Arabidopsis thaliana. The transgenic plants exhibited abnormal shoot development and noticeably smaller leaves, with leaf area reduced to only 13% of wild-type levels. These functional data support the conclusion that CsKNOX6 acts as a negative regulator of bud and leaf size.

“Bud size is a critical trait for both agronomic productivity and market quality of tea. Identification of CsKNOX6 provides a direct genetic target for selective breedingincluding improvement with markers,” the researchers emphasized.

“Although functional testing in Arabidopsis provides strong support, future gene editing or transgenic testing of tea plants will be important to confirm regulatory mechanisms in perennial woody species. This discovery lays the foundation for precision breeding strategies to improve the yield, uniformity and suitability of tea varieties.”

The identification of CsKNOX6 opens new opportunities for the development of tea varieties with optimized bud size for various production purposes, such as premium hand-picked tea or high-yield mechanically harvested tea. The gene can be integrated into molecular breeding programs through SNP marker selection or gene editing approaches to fine-tune developmental growth. In addition, the digital phenotyping methods used in this study provide an efficient basis for assessing shoot characteristics in large germplasm collections.

Ultimately, this work advances genetic improvement strategies that can improve tea yield, processing quality, and economic value.