Artemisia argyi Levl. et Van is an important Asteraceae species with a high medicinal value. There are abundant A. argyi germplasm resources in Asia, especially in China, but the evolutionary relationships of these varieties and the systematic localization of A. argyi in the family Asteraceae are still unclear. In this study, the chloroplast (cp) genomes of 72 A. argyi varieties were systematically analyzed. The 72 varieties originated from 47 regions in China at different longitudes, latitudes and altitudes, and included both wild and cultivated varieties. The A. argyi cp genome was found to be ∼151 kb in size and to contain 114 genes, including 82 protein-coding, 28 tRNA, and 4 rRNA genes. The number of short sequence repeats (SSRs) in A. argyi cp genomes ranged from 35 to 42, and most of them were mononucleotide A/T repeats. A total of 196 polymorphic sites were detected in the cp genomes of the 72 varieties. Phylogenetic analysis demonstrated that the genetic relationship between A. argyi varieties had a weak relationship with their geographical distribution. Furthermore, inverted repeat (IR) boundaries of 10 Artemisia species were found to be significantly different. A sequence divergence analysis of Asteraceae cp genomes showed that the variable regions were mostly located in single-copy (SC) regions and that the coding regions were more conserved than the non-coding regions. A phylogenetic tree was constructed using 43 protein-coding genes common to 67 Asteraceae species. The resulting tree was consistent with the traditional classification system; Artemisia species were clustered into one group, and A. argyi was shown to be closely related to Artemisia lactiflora and Artemisia montana. In summary, this study systematically analyzed the cp genome characteristics of A. argyi and compared cp genomes of Asteraceae species. The results provide valuable information for the definitive identification of A. argyi varieties and for the understanding of the evolutionary relationships between Asteraceae species.

Tea is a popular beverage with characteristic functional and flavor qualities, known to be rich in bioactive metabolites such as tea polyphenols and theanine. Recently, tea varieties with variations in leaf color have been widely used in agriculture production due to their potential advantages in terms of tea quality. Numerous studies have used genome, transcriptome, metabolome, proteome, and lipidome methods to uncover the causes of leaf color variations and investigate their impacts on the accumulation of crucial bioactive metabolites in tea plants. Through a comprehensive review of various omics investigations, we note that decreased expression levels of critical genes in the biosynthesis of chlorophyll and carotenoids, activated chlorophyll degradation, and an impaired photosynthetic chain function are related to the chlorina phenotype in tea plants. For purple-leaf tea, increased expression levels of late biosynthetic genes in the flavonoid synthesis pathway and anthocyanin transport genes are the major and common causes of purple coloration. We have also summarized the influence of leaf color variation on amino acid, polyphenol, and lipid contents and put forward possible causes of these metabolic changes. Finally, this review further proposes the research demands in this field in the future.

Leaf senescence, an essential component of the plant life cycle, seriously affects the productivity of numerous commercial crops, with cytokinins serving as crucial regulators in delaying this process. Here, we observed that apple (Malus domestica) leaves exhibiting deficiencies in sorbitol synthesis due to antisense inhibition of ALOSE-6PHOSPHATE REDUCTASE (A6PR) presented an increase in cytokinin content and exhibited a delay in leaf senescence, in contrast to wild-type (WT) leaves. Transcriptome analysis indicated that the expression of cytokinin oxidase 7 (MdCKX7), encoding a key enzyme in the cytokinin degradation pathway, was significantly downregulated in the A6PR antisense lines. Functional verification confirmed that MdCKX7 facilitated the degradation of cytokinin and accelerated leaf senescence. Moreover, this leaf senescence phenotype was exacerbated by the co-expression of two DNA-binding One Zinc Finger (DOF) transcription factors, cycling DOF factor 3 (MdCDOF3) and MdDOF3.6, along with MdCKX7. Further biochemical and phenotypic analyses demonstrated that MdCDOF3 and MdDOF3.6 bind directly to the promoter region of MdCKX7, thereby transcriptionally activating its expression. Intriguingly, the expression of MdCDOF3, MdDOF3.6, and MdCKX7 is cooperatively induced by sorbitol. These findings demonstrate that the MdCDOF3/MdDOF3.6-MdCKX7 regulatory module orchestrates leaf senescence by facilitating cytokinin degradation in response to sorbitol signaling, revealing a mechanism by which sorbitol signaling modulates leaf senescence specifically through MdCKX7-mediated cytokinin degradation in apple plants.

Artemisia argyi Levl. et Van (A. argyi) is a traditional medicinal plant, which is widely used in health, food and medicine. Thujone is an important cyclic monoterpene derivative in the volatile oil of A. argyi leaves with multiple efficacy. Although the thujone synthetic pathway has been preliminarily analyzed in very few species, genes related to the thujone content in A. argyi leaves remain largely unknown. In this study, we identify candidate genes involved in the synthesis and regulation of thujone content in A. argyi leaves by the comparative transcriptome analysis of two group materials with high and low thujone content. A total of 89 candidate genes related to thujone content are identified including one gene involved in the mevalonate pathway, three genes involved in the methylerythritol phosphate pathway, 19 genes involved in the metabolic process from geranyl pyrophosphate to thujone (four b-terpene synthase, five cytochrome P450, five dehydrogenase, and five reductase-encoding genes) and 66 transcription factor-encoding genes. Taken together, our results provide valuable gene resources for further analyzing the synthetic and regulatory pathway of thujone in A. argyi.