Integration of digital phenotyping, GWAS, and transcriptomic analysis revealed a key gene for bud size in tea plant (Camellia sinensis)

Abstract

Tea plant (Camellia sinensis) is among the most significant beverage crops globally. The size of tea buds not only directly affects the yield and quality of fresh leaves, but also plays a key role in determining the suitability of different types of tea. Analyzing the genetic regulation mechanism of tea bud size is crucial for enhancing tea cultivars and boosting tea yield. In this study, a digital phenotyping technology was utilized to collected morphological characteristics of the apical buds of 280 tea accessions of representative germplasm at the ‘two and a bud’ stage. Genetic diversity analysis revealed that the length, width, perimeter, and area of tea buds followed a normal distribution and exhibited considerable variation across natural population of tea plants. Comparative transcriptomic analysis of phenotypic extreme materials revealed a strong negative correlation between the expression levels of four KNOX genes and tea bud size. A key candidate gene, CsKNOX6, was confirmed by further genome-wide association studies (GWAS). Its function was preliminarily characterized by heterologous transformation of Arabidopsis thaliana. Overexpression of CsKNOX6 reduced the leaf area in transgenic plants, which initially determined that it is a key gene negatively regulating bud size. These findings enhance our understanding of the role of KNOX genes in tea plants and provide some references for uncovering the genetic regulatory mechanisms behind tea bud size.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (U22A20500, 32202553), the Guangxi Key Research and Development Program (AB23026086), the Earmarked Fund for China Agriculture Research System of MOF and MARA (CARS-19), Jiangxi Province Talent Plan (jxsq2023102020), the Major Project of Agricultural Science and Technology in Breeding of Tea Plant Variety in Zhejiang Province (2021C02067) and the Fundamental Research Fund for Tea Research Institute of the Chinese Academy of Agricultural Sciences (1610212023003).

Author contributions

L.C. and J.C. conceived and designed the experiments. S.Z., S.C., Z.F., F.L., and Q.C. performed the experiments. S.Z., S.C., J.M., and J.C. analyzed the data. S.Z., S.C., and J.C. wrote the manuscript. All authors discussed the results and reviewed the final manuscript.

Data availability

The clean sequencing data for this study can be found in the CNCB (www.cncb.ac.cn) Genome Sequence Archive (GSA) under the BioProject accession no. PRJCA031997.

Conflict of interests

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Supplementary data

Supplementary data is available at Horticulture Research online.

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