Comparative transcriptome analysis reveals key pathways and genes involved in trichome development in tea plant (Camellia sinensis)

Authors: CHEN, LAN - Hunan Agricultural University; TIAN, NA - Hunan Agricultural University; HU, MENGQING - Hunan Academy Of Agricultural Sciences; Sandhu, Devinder; JIN, QIFANG - Hunan Agricultural University; GU, MEIYI - Hunan Agricultural University; ZHANG, XIANGQIN - Hunan Agricultural University; PENG, YING - Hunan Agricultural University; ZHANG, JIALI - Hunan Agricultural University; CHEN, ZHENYAN - Hunan Agricultural University; LIU, GUIZHI - Hunan Agricultural University; HUANG, MENGDI - Hunan Agricultural University; HUANG, JIANAN - Hunan Agricultural University; LIU, ZHOUNGHUA - Hunan Agricultural University; LIU, SHUOQUIAN - Hunan Agricultural University

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/19/2022
Publication Date: 9/23/2022
Citation: Chen, L., Tian, N., Hu, M., Sandhu, D., Jin, Q., Gu, M., Zhang, X., Peng, Y., Zhang, J., Chen, Z., Liu, G., Huang, M., Huang, J., Liu, Z., Liu, S. 2022. Comparative transcriptome analysis reveals key pathways and genes involved in trichome development in tea plant (Camellia sinensis). Frontiers in Plant Science. 13. Article 997778. https://doi.org/10.3389/fpls.2022.997778.
DOI: https://doi.org/10.3389/fpls.2022.997778

Interpretive Summary: Tea plants containing outgrowths on leaves called trichomes produce higher quality tea. Thus, developing tea cultivars with more trichomes is an important goal of breeding programs. However, the molecular mechanism regulating tea trichome morphogenesis is not well understood, thus limiting the use of genetic technologies to accelerate tea genetic improvement. This study conducted a genome-wide comparative transcriptome analysis between the hairless (few trichomes) ‘Chuyeqi’ and hairy ‘Budiaomao’ tea cultivars to understand functional genes and biological processes involved in trichome development. Trichomes in both ‘Chuyeqi’ and hairy ‘Budiaomao’ tea cultivars were unicellular, unbranched, straight, and soft type, with high trichome density in newly budded leaves and gradually decreased in the developed leaves. Sequence analysis identified more than 31,000 differentially expressed genes. Five of the differentially expressed genes encoding transcription factors were predicted as potential candidate genes involved in trichome development. A wide variety of genes contributed toward trichome development, including cell cycle, cytoskeleton biosynthesis, and cell wall material biosynthesis. This understanding may help breeders and geneticists develop new tea genotypes with high trichome counts that are tolerant to various biotic and abiotic stresses and produce high-quality tea products. This study may also lay a foundation for additional trichome studies in tea and other crop plants.

Technical Abstract: Trichomes, which develop from epidermal cells, are considered one of the important characteristics of the tea plant [Camellia sinensis (L.) O. Kuntze]. Many nutritional and metabolomic studies have indicated the important contributions of trichomes to tea products quality. However, understanding the regulation of trichome formation at the molecular level remains elusive in tea plants. Herein, we present a genome-wide comparative transcriptome analysis between the hairless Chuyeqi (CYQ) with fewer trichomes and the hairy Budiaomao (BDM) with more trichomes tea plant genotypes, toward the identification of biological processes and functional gene activities that occur during trichome development. In the present study, trichomes in both cultivars CYQ and BDM were unicellular, unbranched, straight, and soft-structured. The density of trichomes was the highest in the bud and tender leaf periods. Further, using the high-throughput sequencing method, we identified 48,856 unigenes, of which 31,574 were differentially expressed. In an analysis of 208 differentially expressed genes (DEGs) encoding transcription factors (TFs), five may involve in trichome development. In addition, on the basis of the Gene Ontology (GO) annotation and the weighted gene co-expression network analysis (WGCNA) results, we screened several DEGs that may contribute to trichome growth, including 66 DEGs related to plant resistance genes (PRGs), 172 DEGs related to cell wall biosynthesis pathway, 29 DEGs related to cell cycle pathway, and 45 DEGs related to cytoskeleton biosynthesis. Collectively, this study provided high-quality RNA-seq information to improve our understanding of the molecular regulatory mechanism of trichome development and lay a foundation for additional trichome studies in tea plants.