Tea (Camelliasinensis) is the world’s most widely consumed non-alcoholic beverage with essential economic and health benefits since it is an excellent source of polyphenols, catechins, amino acids, flavonoids, carotenoids, vitamins, and polysaccharides. The aim of this review is to summarize the main secondary metabolites in tea plants, and the content and distribution of these compounds in six different types of tea and different organs of tea plant were further investigated. The application of these secondary metabolites on food processing, cosmetics industry, and pharmaceutical industry was reviewed in this study. With the rapid advancements in biotechnology and sequencing technology, omics analyses, including genome, transcriptome, and metabolome, were widely used to detect the main secondary metabolites and their molecular regulatory mechanisms in tea plants. Numerous functional genes and regulatory factors have been discovered, studied, and applied to improve tea plants. Research advances, including secondary metabolites, applications, omics research, and functional gene mining, are comprehensively reviewed here. Further exploration and application trends are briefly described. This review provides a reference for basic and applied research on tea plants.

Heavy metal-associated isoprenylated plant proteins (HIPPs) are only distributed in vascular plants, and are essential for the detoxification and vascular transport of heavy metals in plants. However, the HIPP gene family has not been thoroughly explored in the tea plant (Camellia sinensis). In this study, we systematically identified 56C. sinensis CsHIPP genes from five groups and characterized their phylogeny, structures, and the features of the encoded proteins. The expression patterns of CsHIPP genes in various tissues of C. sinensis were investigated based on a previous RNA-seq data analysis. The expression patterns of CsHIPP genes were explored in cadmium (Cd)-treated C. sinensis roots using our RNA-seq data. Three CsHIPP genes (CsHIPP22, CsHIPP24, and CsHIPP36) with high expression levels in Cd-treated C. sinensis roots were selected as candidate genes associated with Cd tolerance. Overexpression of CsHIPP22, CsHIPP24, and CsHIPP36 in a yeast mutant (ycf1) rescued Cd-sensitive ycf1 yeast and increased the yeast resistance to Cd stress, implying that these three CsHIPPs might be involved in Cd tolerance. These findings will enable the roles of HIPPs in Cd absorption and detoxification to be better understood as well as improving our understanding of the Cd-resistance and Cd-accumulation mechanisms in tea plant.

The transcription factors (TFs) family known as the basic leucine zipper (bZIP) plays a vital role in a variety of biological processes. However, there is no investigation on the bZIP family in the major vegetable crop, eggplant. Here, a total of 71 SmbZIP genes were identified from the eggplant genome and compared with other 18 representative plants. According to the topology of the phylogenetic tree, as well as the categorization and nomenclature of bZIP genes in Arabidopsis and Solanum lycopersicum, the SmbZIP family was classified into 13 groups. Analysis of the chromosome location, motif composition and gene structure of the SmbZIP genes were also performed. Gene duplication analysis revealed that the expansion of the SmbZIP genes was mainly attributed to WGD/segmental duplication. Promoter analysis of the SmbZIP genes and examination of the expression patterns of SmbZIP genes under four abiotic pressures revealed that many SmbZIP genes are related to the control of abiotic stresses. Altogether, the identification, categorization, phylogenetic analysis, chromosome distribution, motif composition, and expression patterns of SmbZIPs were predicted and examined. Importantly, this investigation of SmbZIPs offers a wealth of information that will assist researchers in better understanding their function in eggplant.

Black spot, caused by Alternaria brassicicola (Ab), poses a serious threat to crucifer production, and knowledge of how plants respond to Ab infection is essential for black spot management. In the current study, combined transcriptomic and metabolic analysis was employed to investigate the response to Ab infection in two cabbage (Brassica oleracea var. capitata) genotypes, Bo257 (resistant to Ab) and Bo190 (susceptible to Ab). A total of 1100 and 7490 differentially expressed genes were identified in Bo257 (R_mock vs. R_Ab) and Bo190 (S_mock vs. S_Ab), respectively. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that “metabolic pathways”, “biosynthesis of secondary metabolites”, and “glucosinolate biosynthesis” were the top three enriched KEGG pathways in Bo257, while “metabolic pathways”, “biosynthesis of secondary metabolites”, and “carbon metabolism” were the top three enriched KEGG pathways in Bo190. Further analysis showed that genes involved in extracellular reactive oxygen species (ROS) production, jasmonic acid signaling pathway, and indolic glucosinolate biosynthesis pathway were differentially expressed in response to Ab infection. Notably, when infected with Ab, genes involved in extracellular ROS production were largely unchanged in Bo257, whereas most of these genes were upregulated in Bo190. Metabolic profiling revealed 24 and 56 differentially accumulated metabolites in Bo257 and Bo190, respectively, with the majority being primary metabolites. Further analysis revealed that dramatic accumulation of succinate was observed in Bo257 and Bo190, which may provide energy for resistance responses against Ab infection via the tricarboxylic acid cycle pathway. Collectively, this study provides comprehensive insights into the Ab–cabbage interactions and helps uncover targets for breeding Ab-resistant varieties in cabbage.