Tea plants (Camellia sinensis) are perennial crops rich in health-promoting compounds, including amino acids like theanine. During early growth, seedlings rely on internal reserves of carbon and nitrogen to fuel development. However, the spatial dynamics of metabolite synthesis and distribution have remained largely unexplored. Conventional metabolomic methods often destroy tissue structures, making it hard to visualize these biochemical processes in situ. Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) offers a solution by preserving tissue architecture while mapping molecular distributions. Due to these limitations and the importance of nitrogen and sugar metabolism in tea development, a detailed in situ analysis of metabolite dynamics is urgently needed.
A research team from Anhui Agricultural University and South-Central Minzu University published a study (DOI: 10.1093/hr/uhae218) on August 3, 2024, in Horticulture Research, employing MALDI-MSI to visualize the spatial distribution of 1,234 metabolites in tea seedlings. Their findings reveal a central role for theanine in nitrogen transport and storage, and demonstrate the coordinated movement of sugars and amino acids that drive tissue differentiation during early development.
The researchers collected tea seedlings at different growth stages and sliced them for MALDI-MSI analysis, identifying 1,234 metabolites grouped into 24 categories. Among these, theanine stood out—accounting for over 80% of total free amino acids in roots and stems at key stages. It was synthesized rapidly during radicle germination and localized mainly in root meristem tissues before being transported to the shoot tip, indicating its role as a key nitrogen carrier. Interestingly, while glutamine and glutamate were also present, only theanine showed distinct spatiotemporal accumulation patterns.
In terms of carbon metabolism, the cotyledons stored carbohydrates like dextrin and 3-phosphoglyceraldehyde, which were gradually mobilized and converted to glucose and raffinose. These sugars were primarily found in actively growing regions such as root tips and apical meristems. The researchers also detected hormones like auxin and abscisic acid, though in low abundance, indicating their involvement in regulating germination and early root/shoot formation. Taken together, the study provides a comprehensive metabolic map and offers insights into how tea seedlings orchestrate nitrogen and carbon flows during early development.
“Our research offers the first tissue-level view of how tea seedlings manage nutrient flows during early development,” said Prof. Qi Chen, co-corresponding author of the study. “The dominance of theanine as a nitrogen form and its targeted distribution suggest that it may act not only as a nutrient but also as a signaling molecule. These findings deepen our understanding of tea biology and could have implications for improving seedling vigor and breeding strategies.”
This spatial metabolomic approach lays the foundation for precision breeding of tea plants. By revealing how theanine and other metabolites are synthesized, transported, and utilized, the study opens new avenues for enhancing seedling vigor and stress resilience. The clear visualization of key carbon and nitrogen compounds at specific developmental stages could help identify biomarkers for early selection of high-performance tea varieties. Moreover, the MALDI-MSI technique used here can be extended to other crops, offering a powerful tool to decode nutrient dynamics and support crop improvement across species.
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References
DOI
10.1093/hr/uhae218
Original Source URL
https://doi.org/10.1093/hr/uhae218
Funding information
The authors are grateful for financial support from the National Key Research and Development Program of China (2022YFF1003103) and the Scientific Research Projects of University in Anhui Province (2023AH051044).
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2023. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.