Background Trichomes play a key role in the development of plants and exist in a wide variety of species. Results In this paper, it was reviewed that the structure and morphology characteristics of trichomes, alongside the biological functions and classical regulatory mechanisms of trichome development in plants. The environment factors, hormones, transcription factor, non-coding RNA, etc., play important roles in regulating the initialization, branching, growth, and development of trichomes. In addition, it was further investigated the atypical regulation mechanism in a non-model plant, found that regulating the growth and development of tea (Camellia sinensis) trichome is mainly affected by hormones and the novel regulation factors. Conclusions This review further displayed the complex and differential regulatory networks in trichome initiation and development, provided a reference for basic and applied research on trichomes in plants.

In this study, we performed an association analysis of metabolomics and transcriptomics to reveal the anthocyanin biosynthesis mechanism in a new purple-leaf tea cultivar Zikui (Camellia sinensis cv. Zikui) (ZK). Three glycosylated anthocyanins were identified, including petunidin 3-O-glucoside, cyanidin 3-O-galactoside, and cyanidin 3-O-glucoside, and their contents were the highest in ZK leaves at 15 days. This is the first report on petunidin 3-O-glucoside in purple-leaf tea. Integrated analysis of the transcriptome and metabolome identified eleven dependent transcription factors, among which CsMYB90 had strong correlations with petunidin 3-O-glucoside, cyanidin 3-O-galactoside, and cyanidin 3-O-glucoside (PCC > 0.8). Furthermore, we also identified key correlated structural genes, including two positively correlated F3’H (flavonoid-3′-hydroxylase) genes, two positively correlated ANS (anthocyanin synthase) genes, and three negatively correlated PPO (polyphenol oxidase) genes. Overexpression of CsMYB90 in tobacco resulted in dark-purple transgenic calluses. These results showed that the increased accumulation of three anthocyanins in ZK may promote purple-leaf coloration because of changes in the expression levels of genes, including CsMYB90, F3’Hs, ANSs, and PPOs. These findings reveal new insight into the molecular mechanism of anthocyanin biosynthesis in purple-leaf tea plants and provide a series of candidate genes for the breeding of anthocyanin-rich cultivars.

Duyun Maojian tea is a famous tea in China. In this study, the specific-locus amplified fragment (SLAF) sequencing method was used to analyze the population structure and conduct a genome-wide association study (GWAS) of 2 leaf traits of 123 tea plants in Qiannan, China. A total of 462,019 SLAF tags and 11,362,041 single-nucleotide polymorphism (SNP) loci were obtained. The results of phylogenetic tree analysis, cluster analysis, and principal component analysis showed that 123 tea germplasms were clustered into three groups, and the heterozygosity rates for Groups I, II, and II were 0.206, 0.224, and 0.34, respectively. Generally, tea germplasms in a production area are clustered in a group, indicating that tea germplasms in different production areas have certain genetic diversity. The traditional Duyun Maojian tea core production areas, TS and DC-SJ, are clustered into Group I and Group II respectively, while the ZY production area is relatively independent in Group III. Furthermore, based on GWAS analysis, 11 candidate genes related to leaf apex and 7 candidate genes related to leaf shape were obtained. This study clarified the genetic relationship among eight Duyun Maojian tea production areas and obtained candidate genes related to leaf apex and leaf shape development. The results showed that population structure and candidate genes are an effective basis for the breeding of Duyun Maojian tea germplasm.

The ERF gene family is widely present in plants and has crucial regulatory importance in plant seed development, organ morphogenesis, the synthesis of secondary metabolites, and coping with abiotic stresses such as cold and drought. In this study, 90 members of CsERF were screened by bioinformatics tools analysis and named CsERF1–CsERF90. Their molecular characteristics and systematic evolution were studied, and the tissue expression characteristics of CSERF genes and the composition of promoter cis-acting elements were predicted. The results showed that 81 proteins encoded by CsERF genes had conserved motifs 1, 2, and 3, while 64 members possessed other motifs. The theoretical isoelectric point was between 4.49 and 10.24, and 85 members constituted unstable proteins, while the rest were stable proteins. Subcellular localization predicted that 77 members were in the nucleus, 8 were in the chloroplasts, and 5 were in the mitochondria. The promoter sequence of CsERFs was found to include not only cis-acting elements related to hormone regulation, such as gibberellin (41), methyl jasmonate (110), and abscisic acid (185), but also cis-acting elements involved in low-temperature response (56) and light response (22), indicating that CsERFs have a key role in plant growth and abiotic stress. Phylogenetic analysis of tea plant and Arabidopsis thaliana ERF gene families showed that the tea plant ERF gene families could be divided into six groups, with B3 having 29 members at most and B1 having only 3 members at least. The phylogenetic tree constructed using only the CsERF genes is also divided into six groups, with slightly different but minimal differences in members. Of the 90 tea plant ERF members, 85 were located on 15 chromosomes, whereas 5 were not located on chromosomes. The collinearity analysis showed that there were 41 homologous gene pairs among the CsERFs, and these homologous gene pairs may have the same function. According to the expression of CsERFs in cold-stressed tea plant and in different tissues, 90 CsERF genes played their respective roles in different tissues and stages to regulate plant growth, and some of them participated in the process of cold stress tolerance. This study provides a theoretical foundation for the study of tea plant growth and development and low-temperature resistance.

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