Abstract
Trichomes, which develop from epidermal cells, are regarded as one of the key features that are involved in the evaluation of tea quality and tea germplasm resources. The metabolites from trichomes have been well characterized in tea products. However, little is known regarding the metabolites in fresh tea trichomes and the molecular differences in trichomes and tea leaves per se. In this study, we developed a method to collect trichomes from tea plant tender shoots, and their main secondary metabolites, including catechins, caffeine, amino acids, and aroma compounds, were determined. We found that the majority of these compounds were significantly less abundant in trichomes than in tea leaves. RNA-Seq was used to investigate the differences in the molecular regulatory mechanism between trichomes and leaves to gain further insight into the differences in trichomes and tea leaves. In total, 52.96 Gb of clean data were generated, and 6560 differentially expressed genes (DEGs), including 4471 upregulated and 2089 downregulated genes, were identified in the trichomes vs. leaves comparison. Notably, the structural genes of the major metabolite biosynthesis pathways, transcription factors, and other key DEGs were identified and comparatively analyzed between trichomes and leaves, while trichome-specific genes were also identified. Our results provide new insights into the differences between tea trichomes and leaves at the metabolic and transcriptomic levels, and open up new doors to further recognize and re-evaluate the role of trichomes in tea quality formation and tea plant growth and development.
Highlights
Trichomes are developed from epidermal cells and they can be uni- or multicellular, glandular or non-glandular, branched or unbranched, and extensively distributed on plant tissues, playing critical roles in plant growth and the development and stress responses [1,2,3,4,5,6]
Threonine was not detected in trichomes, and serine was not detected in leaves
We found that most gene family members, such as cupin superfamily proteins, GDSL-type lipase/esterase, glutathione S-transferase (GST), cellulose synthase (CesA), terpene synthase (TPS), peroxidase, and pectinesterase, which are generally involved in cell wall synthesis and abiotic stress response, were significantly upregulated in trichomes (Figure 5)
Summary
Trichomes are developed from epidermal cells and they can be uni- or multicellular, glandular or non-glandular, branched or unbranched, and extensively distributed on plant tissues, playing critical roles in plant growth and the development and stress responses [1,2,3,4,5,6]. It has been well established that the most notable difference between glandular and non-glandular trichomes is that glandular trichomes have the capability to synthesize, store, and secrete a wide variety of metabolites, including polysaccharides, organic acids, proteins, terpenoids, alkaloids, and polyphenols [1,5,8,9], suggesting that tea trichomes may not have the capability to synthesize, store, or secrete these metabolites. Several previous studies showed that tea trichomes had a wide variety of metabolites, such as catechins, caffeine, amino acids, and aromatic compounds. Given that almost all tea plant cultivars or germplasm resources have trichomes on the tender shoot surfaces, if these trichomes do not synthesize metabolites, what is their function in the tea plant?
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
