Young leaves and buds of Camellia sinensis are the principal raw materials used to produce tea, and their size and shape influence harvesting, grading, processing, flavor, and appearance. Cytokinins are plant hormones known to coordinate cell division, cell expansion, shoot meristem activity, and leaf growth. Their abundance is controlled partly by isopentenyltransferases, which promote cytokinin biosynthesis, and cytokinin oxidases/dehydrogenases, which irreversibly degrade the hormones. Although these pathways have been investigated in several model and crop plants, their contribution to leaf development in tea remains poorly understood. Moreover, constitutive manipulation of cytokinin-related genes may disrupt roots and other organs, creating a need for tissue-specific regulatory systems that modify leaves without causing widespread developmental abnormalities.
A study (DOI: 10.48130/bpr-0026-0016) published in Beverage Plant Research on 31 August 2026 by Suzhen Niu's & Xiaojing Wang's team, Guizhou University, reports that targeted expression of these two genes raises or lowers cytokinin accumulation, respectively, thereby producing contrasting changes in leaf cell structure and overall leaf size.
The researchers first searched the genomes of 22 tea cultivars and identified 216 IPT and 204 CKX family genes. Phylogenetic and transcriptomic analyses revealed their evolutionary relationships and organ-specific expression patterns, while expression profiling in the ‘Shuchazao’ cultivar highlighted CsIPT3 and CsCKX5 as candidates associated with above-ground tissues and leaf development. Fluorescent-protein assays further localized both encoded proteins to the nucleus and plasma membrane. To develop a targeted expression system, the team examined four promoters from shoot-enriched CsLhc genes. Reporter assays in tobacco leaves showed that the CsLhc11 promoter had the strongest activity, comparable to that of the widely used constitutive CaMV 35S promoter. The researchers then used this promoter to drive CsIPT3 or CsCKX5 expression in transgenic A. thaliana. Ultra-performance liquid chromatography-tandem mass spectrometry showed that total cytokinin content increased by 35.74% in CsIPT3-expressing plants but decreased by 62.18% in CsCKX5-expressing plants relative to wild-type controls. Correspondingly, CsIPT3 expression increased leaf length by 29.75% and width by 19.56%, whereas CsCKX5 expression reduced these dimensions by 22.46% and 19.90%, respectively. Scanning electron microscopy revealed larger, more loosely arranged cells and wider intercellular spaces in CsIPT3-expressing leaves, while CsCKX5-expressing leaves contained smaller, tightly packed cells. Six cytokinin-responsive genes related to cell division and expansion were also upregulated by CsIPT3 and downregulated by CsCKX5. Importantly, the shoot-specific treatments altered leaf growth without producing visible abnormalities in overall plant development.
Together, the results establish a functional connection between two tea genes, cytokinin homeostasis, cellular architecture, and leaf morphology. The strong shoot-associated CsLhc11 promoter may also provide a useful tool for directing gene expression toward aerial tissues while limiting unwanted effects elsewhere. Because functional validation was conducted in transgenic A. thaliana rather than genetically transformed tea plants, further studies are needed to confirm these mechanisms directly in tea. Nevertheless, the work supplies candidate genes and a targeted regulatory strategy for future improvement of tea leaf traits and for investigating possible links between cytokinin levels and quality-related compounds such as catechins, theanine, and caffeine.
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References
DOI
10.48130/bpr-0026-0016
Original Source URL
https://doi.org/10.48130/bpr-0026-0016
Funding information
This work was supported by the Guizhou Provincial Science and Technology Projects (Qiankehe Jichu-ZK [2022] General 111).
About Beverage Plant Research
Beverage Plant Research (e-ISSN 2769-2108) is the official journal of Tea Research Institute, Chinese Academy of Agricultural Sciences and China Tea Science Society. Beverage Plant Research is an open-access, online-only journal published by Maximum Academic Press. Beverage Plant Research publishes original research, methods, reviews, editorials, and perspectives that advance the biology, chemistry, processing, and health functions of tea and other important beverage plants.