Human activities, such as mining, industrialization, industrial waste emissions, and agricultural practices, have caused heavy metals to become widespread and excessively accumulated in soil. The high concentrations of heavy metals in soil can be toxic to plants, severely affecting crop yield and quality. Moreover, these heavy metals can also enter the food chain, affecting animals and humans and leading to various serious illnesses. Selenium (Se) is not only an essential element for animals and humans but is also beneficial for plants, as it promotes their ability to respond actively to biotic and abiotic stresses. The global issue of Se deficiency in diets has made plants the primary source for human Se supplementation. This paper comprehensively reviews the effects of heavy metal stress on plant growth and development, physiological responses of plants to such stress, and the intracellular transport processes of heavy metals within plants. It particularly focuses on the mechanisms by which Se alleviates heavy metal stress in plants. Additionally, the study delves into how Se significantly enhances plant tolerance mechanisms against typical heavy metals, such as cadmium (Cd), lead (Pb), and mercury (Hg). This integrative research not only expands the boundaries of research in the field of plant heavy metal stress and Se application but also provides new perspectives and solutions for understanding and addressing complex environmental heavy metal pollution issues. By integrating these aspects, this paper not only fills existing gaps in the literature but also offers comprehensive scientific basis and strategic recommendations for environmental protection and sustainable agriculture development.

Terpene trilactones (TTLs) are important secondary metabolites in ginkgo (Ginkgo biloba); however, their biosynthesis gene regulatory network remains unclear. Here, we isolated a G. biloba ethylene response factors 4 (GbERF4) involved in TTL synthesis. Overexpression of GbERF4 in tobacco (Nicotiana tabacum) significantly increased terpenoid content and upregulated the expression of key enzyme genes (3-hydroxy-3-methylglutaryl-CoA reductase (HMGR), 3-hydroxy-3-methylglutaryl-CoA synthase (HMGS), 1-deoxy-D-xylulose-5-phosphate reductoisomerase (DXR), 1-deoxy-D-xylulose-5-phosphate synthase (DXS), acetyl-CoA C-acetyltransferase (AACT), and geranylgeranyl diphosphate synthase (GGPPS)) in the terpenoid pathway in tobacco, suggesting that GbERF4 functions in regulating the synthesis of terpenoids. The expression pattern analysis and previous microRNA (miRNA) sequencing showed that gb-miR160 negatively regulates the biosynthesis of TTLs. Transgenic experiments showed that overexpression of gb-miR160 could significantly inhibit the accumulation of terpenoids in tobacco. Targeted inhibition and dual-luciferase reporter assays confirmed that gb-miR160 targets and negatively regulates GbERF4. Transient overexpression of GbERF4 increased TTL content in G. biloba, and further transcriptome analysis revealed that DXS, HMGS, CYPs, and transcription factor genes were upregulated. In addition, yeast one-hybrid and dual-luciferase reporter assays showed that GbERF4 could bind to the promoters of the HMGS1, AACT1, DXS1, levopimaradiene synthase (LPS2), and GGPPS2 genes in the TTL biosynthesis pathway and activate their expression. In summary, this study investigated the molecular mechanism of the gb-miR160-GbERF4 regulatory module in regulating the synthesis of TTLs. It provides information for enriching the understanding of the regulatory network of TTL biosynthesis and offers important gene resources for the genetic improvement of G. biloba with high contents of TTLs.

As a traditional spicy condiment, Zanthoxylum armatum var. novemfolius is of high economical and medicinal value. Despite the long history of human cultivation, the molecular mechanisms underlying flower development are still poorly understood in Z. armatum. In this study, we performed de novo transcriptome assembly and comparative analysis of female and male flowers in Z. armatum. A total of 94,771 unigenes were obtained, and 50,605 unigenes were successfully annotated against the public database. Transcriptome data showed that 20,431 annotated unigenes were differentially expressed genes. KEGG enrichment analysis revealed that the most representative pathway was plant hormone signal transduction. Among them, 41, 16, 41, 27, 95, and 40 unigenes were involved in the biosynthesis and signaling of abscisic acid, ethylene, cytokinin, gibberellin, auxin, and jasmonic acid, respectively. Transcription factors also played crucial roles in flower development, such as AGL11, PMADS2, and NAC. These results provided an important basis for characterizing the potential mechanism of flower development and enriching the knowledge of reproduction genetics in Z. armatum.

Background: Ginkgo biloba, a typical dioecious plant, is a traditional medicinal plant widely planted. However, it has a long juvenile period, which severely affected the breeding and cultivation of superior ginkgo varieties. Results: In order to clarify the complex mechanism of sexual differentiation in G. biloba strobili. Here, a total of 3293 miRNAs were identified in buds and strobili of G. biloba, including 1085 known miRNAs and 2208 novel miRNAs using the three sequencing approaches of transcriptome, small RNA, and degradome. Comparative transcriptome analysis screened 4346 and 7087 differentially expressed genes (DEGs) in male buds (MB) _vs_ female buds (FB) and microstrobilus (MS) _vs_ ovulate strobilus (OS), respectively. A total of 6032 target genes were predicted for differentially expressed miRNA. The combined analysis of both small RNA and transcriptome datasets identified 51 miRNA-mRNA interaction pairs that may be involved in the process of G. biloba strobili sexual differentiation, of which 15 pairs were verified in the analysis of degradome sequencing. Conclusions: The comprehensive analysis of the small RNA, RNA and degradome sequencing data in this study provided candidate genes and clarified the regulatory mechanism of sexual differentiation of G. biloba strobili from multiple perspectives.

Ginkgo biloba is widely planted, and the extracts of leaves contain flavonoids, terpene esters and other medicinal active ingredients. WRKY proteins are a large transcription factor family in plants, which play an important role in the regulation of plant secondary metabolism and development, as well as the response to biotic and abiotic stress. In our study, we identified 40 genes with conserved WRKY motifs in the G. biloba genome and classified into groups I (groups I-N and -C), II (groups IIa, b, c, d, and e), and III, which include 12, 26, and 2 GbWRKY genes, respectively. Meanwhile, the expression patterns of 10 GbWRKY (GbWRKY2, GbWRKY3, GbWRKY5, GbWRKY7, GbWRKY11, GbWRKY15, GbWRKY23, GbWRKY29, GbWRKY31, GbWRKY32) under different tissue and abiotic stress conditions were analyzed. Under stress treatment, the expression patterns of 10 WRKY genes were changed. 10 ginkgo WRKY transcription factors were induced by ETH and SA, but there are two different induced response modes. The expression of 10 WRKY genes was inhibited under low temperature, high temperature and MeJA hormone induction. Most WRKY genes were up-regulated under the induction of high salt and ABA. GbWRKYs were differentially expressed in various tissues after abiotic stress and plant hormone treatments, thereby indicating their possible roles in biological processes and abiotic stress tolerance and adaptation. Our results provided insight into the genome-wide identification of GbWRKYs, as well as their differential responses to stresses and hormones. These data can also be utilized to identify potential molecular targets to confer tolerance to various stresses in G. biloba. ********* In press - Online First. Article has been peer reviewed, accepted for publication and published online without pagination. It will receive pagination when the issue will be ready for publishing as a complete number (Volume 47, Issue 4, 2019). The article is searchable and citable by Digital Object Identifier (DOI). DOI link will become active after the article will be included in the complete issue. *********

Cardamine violifolia is a significant Brassicaceae plant known for its high selenium (Se) accumulation capacity, serving as an essential source of Se for both humans and animals. WRKY transcription factors play crucial roles in plant responses to various biotic and abiotic stresses, including cadmium stress, iron deficiency, and Se tolerance. However, the molecular mechanism of CvWRKY in Se accumulation is not completely clear. In this study, 120 WRKYs with conserved domains were identified from C. violifolia and classified into three groups based on phylogenetic relationships, with Group II further subdivided into five subgroups. Gene structure analysis revealed WRKY variations and mutations within the CvWRKYs. Segmental duplication events were identified as the primary driving force behind the expansion of the CvWRKY family, with numerous stress-responsive cis-acting elements found in the promoters of CvWRKYs. Transcriptome analysis of plants treated with exogenous Se and determination of Se levels revealed a strong positive correlation between the expression levels of CvWRKY034 and the Se content. Moreover, CvWRKY021 and CvWRKY099 exhibited high homology with AtWRKY47, a gene involved in regulating Se accumulation in Arabidopsis thaliana. The WRKY domains of CvWRKY021 and AtWRKY47 were highly conserved, and transcriptome data analysis revealed that CvWRKY021 responded to Na2SeO4 induction, showing a positive correlation with the concentration of Na2SeO4 treatment. Under the induction of Na2SeO3, CvWRKY021 and CvWRKY034 were significantly upregulated in the roots but downregulated in the shoots, and the Se content in the roots increased significantly and was mainly concentrated in the roots. CvWRKY021 and CvWRKY034 may be involved in the accumulation of Se in roots. The results of this study elucidate the evolution of CvWRKYs in the C. violifolia genome and provide valuable resources for further understanding the functional characteristics of WRKYs related to Se hyperaccumulation in C. violifolia.