External application of brassinolide enhances cold resistance of tea plants (Camellia sinensis L.) by integrating calcium signals.

MAIN CONCLUSION: Exogenous brassinolide can activate the expression of key genes in the calcium signalling pathway to enhance cold resistance of tea plants. Brassinolide is an endogenous sterol phytohormone containing multiple hydroxyl groups that has the important function of improving plant cold resistance and alleviating freeze damage. To explore the molecular mechanism of how brassinolide improves the cold resistance of tea plants, "Qiancha 1" was used as the material, and the method of spraying brassinolide on the leaves was adopted to explore its effects on the tea plants under 4 °C low-temperature treatment. The results showed that brassinolide can significantly increase the protective enzyme activity of tea plants under cold stress and reduce cold damage. At the transcriptome level, brassinolide significantly enhanced the expression of key genes involved in calcium signal transduction, Calmodulin (CaM), Calcium-dependent protein kinase (CDPK), calcineurin B-like protein (CBL) and calmodulin-binding transcriptional activators (CAMTA), which then activated the downstream key genes transcriptional regulator CBF1 (CBF1) and transcription factor ICE1 (ICE1) during cold induction. Quantitative real-time PCR (qRT‒PCR) results showed that the expression of these genes was significantly induced after treatment with brassinolide, especially CaM and CBF1. When calcium signalling was inhibited, the upregulated expression of CBF1 and ICE1 disappeared, and when CAMTA was knocked down, the expression of other genes under cold stress was also significantly reduced. The above results indicate that brassinolide combined with the calcium signalling pathway can improve the cold resistance of tea plants. This study provides a new theoretical basis for the study of the cold resistance mechanism of brassinolide.

Effects of foliar applications of Brassinolide and Selenium on the accumulation of Arsenic and Cadmium in rice grains and an assessment of their health risk.

Arsenic and cadmium pose a potential health risk to human beings via rice grain consumption. In the current study, a pot experiment was conducted to evaluate the effect of Br (5 mM and 20 mM) and Se (1 mM) at rice tillering and filling stages on Cd and As accumulation in rice grain and their health risk indices. The results showed that Br or Se applications at different stages of rice improved the photosynthesis, reduce MDA content in flag leaves by 17.41%-38.65%, increased rice biomass and grain yield by 10.50%-29.94% and 10.50%-36.56%, and enhanced grain N and P uptake by 3.25%-34.90%, and 22.98%-72.05%, respectively. Applications of Br and Se effectively decreased Cd and As concentration in rice grain by 31.74%-86.97% and 16.42%-81.13% respectively. Compared to the individual treatment, combined 20 mM Br and 1 mM Se at the filling stage showed the lowest accumulation of As (0.149 mg·kg-1) and Cd (0.105 mg·kg-1) in grain, and its health risk index was below the acceptable limits (HRI < 1). This implies that application of Br and Se at the filling stage is a promising strategy for the safe production of rice in As and Cd co-contaminated regions.

In this study, foliar applications of Br and Se at the grain filling and tillering stage demonstrate their effect on As and Cd accumulation. The findings showed that Br and Se resulted in the Se concentration in grains reaching the Se-enriched level, and the accumulation of As and Cd was the lowest. Furthermore, the application of Br and Se decreased lipid peroxidation, promoted N and P uptake, and increased the rate of photosynthesis in the rice plants, which resulted in increasing rice growth and grain yield. The HRI of heavy metals was below the acceptable limits after application of Br and Se.

Transcriptome Analysis Reveals an Essential Role of Exogenous Brassinolide on the Alkaloid Biosynthesis Pathway in Pinellia Ternata.

Pinellia ternata (Thunb.) Druce is a traditional medicinal plant containing a variety of alkaloids, which are important active ingredients. Brassinolide (BR) is a plant hormone that regulates plant response to environmental stress and promotes the accumulation of secondary metabolites in plants. However, the regulatory mechanism of BR-induced alkaloid accumulation in P. ternata is not clear. In this study, we investigated the effects of BR and BR biosynthesis inhibitor (propiconazole, Pcz) treatments on alkaloid biosynthesis in the bulbil of P. ternata. The results showed that total alkaloid content and bulbil yield was enhanced by 90.87% and 29.67% under BR treatment, respectively, compared to the control. We identified 818 (476 up-regulated and 342 down-regulated) and 697 (389 up-regulated and 308 down-regulated) DEGs in the BR-treated and Pcz-treated groups, respectively. Through this annotated data and the Kyoto encyclopedia of genes and genomes (KEGG), the expression patterns of unigenes involved in the ephedrine alkaloid, tropane, piperidine, pyridine alkaloid, indole alkaloid, and isoquinoline alkaloid biosynthesis were observed under BR and Pcz treatments. We identified 11, 8, 2, and 13 unigenes in the ephedrine alkaloid, tropane, piperidine, and pyridine alkaloid, indole alkaloid, and isoquinoline alkaloid biosynthesis, respectively. The expression levels of these unigenes were increased by BR treatment and were decreased by Pcz treatment, compared to the control. The results provided molecular insight into the study of the molecular mechanism of BR-promoted alkaloid biosynthesis.

Physiological and Transcriptomic Analysis provide Molecular Insight into 24-Epibrassinolide mediated Cr(VI)-Toxicity Tolerance in Pepper Plants.

The ever-increasing industrial activities over the decades have generated high toxic metals such as chromium (Cr) that hampers plant growth and development. To counter Cr-toxicity, plants have evolved complex defensive systems including hormonal crosstalk with various signaling pathways. 24-epibrassinolide (24-EBR) lowers oxidative stress and alleviates Cr(VI)-toxicity in plants. In this study, the concealed BR-mediated influences on Cr(VI)-stress tolerance were explored by transcriptome analysis in the Capsicum annuum. Results revealed a linkage between plant development under Cr(VI)-stress and the mitigating effect of 24-epibrassinolide and brassinazole. Growth inhibition, chlorophyll degradation, and a significant rise of malondialdehyde (MDA) were observed after 40 mg/L Cr(VI) treatment in Brz supplemented seedlings, whereas 24-EBR supplemented seedlings exhibited commendatory effect. Comparative transcriptome analysis showed that the expression levels of 6687 genes changed (3846 up-regulated and 2841 downregulated) under Cr(VI)-stress with Brz supplementation. Whereas the expression levels of only 1872 genes changed under Cr(VI)-stress with 24-EBR supplementation (1223 up-regulated and 649 downregulated). The functional categories of the differentially expressed genes (DEGs) by gene ontology (GO) revealed that drug transport, defense responses, and drug catabolic process were the considerable enrichments between 24-EBR and Brz supplemented seedlings under Cr(VI)-stress. Furthermore, auxin signaling, glutathione metabolism, ABC transporters, MAPK pathway, and 36 heavy metal-related genes were significantly differentially expressed components between Cr(VI)-stress, 24-EBR, and Brz supplemented seedlings. Overall, our data demonstrate that employing 24-EBR can commendably act as a growth stimulant in plants subjected to Cr(VI)-stress by modulating the physiological and defense regulatory system.

Identification of differentially expressed miRNAs and their target genes in response to brassinolide treatment on flowering of tree peony (Paeonia ostii).

Tree peony is a famous flower plant in China, but the short and concentrated flowering period limits its ornamental value and economic value. Brassinolide (BR) plays an important role in plant growth and development including flowering. There have been a large number of reports on the molecular aspects of the flowering process, but the genetic mechanism that was responsible for miRNA-guided regulation of tree peony is almost unclear. In this study, the leaves of tree peony cultivar, 'Feng Dan', were sprayed with different concentrations of BR, and the obvious bloom delay was found at the treatment with BR 50 µg/L. The small RNA sequencing and transcriptome sequencing were performed on the petals of tree peony under an untreated control (CK) and the treatment with BR 50 µg/L during four consecutive flowering development stages. A total of 22 known miRNAs belonging to 12 families were identified and 84 novel miRNAs were predicted. Combined with transcriptome data, a total of 376 target genes were predicted for the 18 differentially expressed known miRNAs and 177 target genes were predicted for the 23 differentially expressed novel miRNAs. Additionally, the potential miRNAs and their target genes were identified, including miR156b targeting SPL, miR172a_4 targeting AP2 and four novel miRNAs targeting SPA1, and revealed that they might affect the flowering time in tree peony. Collectively, these results would provide a theoretical basis for further analysis of miRNA-guided regulation on flowering period in tree peony.

Phytoestrogens, phytosteroids and saponins in vegetables: Biosynthesis, functions, health effects and practical applications.

Phytoestrogens are non-steroidal secondary metabolites with similarities in structure and biological activities with human estrogens divided into various classes of compounds, including lignans, isoflavones, ellagitannins, coumestans and stilbenes. Similarly, phytosteroids are steroidal compounds of plant origin which have estrogenic effects and can act as agonists, antagonists, or have a mixed agonistic/antagonistic activity to animal steroid receptors. On the other hand, saponins are widely distributed plant glucosides divided into triterpenoid and steroidal saponins that contribute to plant defense mechanism against herbivores. They present a great variation from a structural point of view, including compounds from different classes. In this chapter, the main vegetable sources of these compounds will be presented, while details regarding their biosynthesis and plant functions will be also discussed. Moreover, considering the significant bioactive properties that these compounds exhibit, special focus will be given on their health effects, either beneficial or adverse. The practical applications of these compounds in agriculture and phytomedicine will be also demonstrated, as well as the future prospects for related research.

[Effect of exogenous brassinolide on morphological characters and contents of seven chemical constituents of Glycyrrhiza uralensis].

The transplants of the two-year-old Glycyrrhiza uralensis were subjected to four concentration of brassinolide (BR 0.1, 0.4, 0.7, 1.0 mg•L⁻¹) in July. The morphological characters ( plant height, stem diameter, nodes number, internode length and root length , root thick, root fresh weight and root dry weight ) were measured and seven kinds of chemical constituents (glycyrrhizic acid, liquiritin, isoliquiritin, liquiritigenin, isoliquiritigenin, liquiritin apioside, isoliquiritin apioside) were determined by HPLC with the aim of increasing sinter output and improving quality of G. uralensis. Then the long-term dynamic changes of these morphological characters and chemical compositions' content were analyzed. The results showed that morphological characters of plant height, stem diameter, root length , root thick, root fresh weight and root dry weight increased remarkably with the 0.7 mg•L⁻¹ BR stimulating 2 months later,the increase rates were： 15.09%,6.15%,16.52%,8.46%,21.90%,29.41%, respectively. The content of glycyrrhizic acid, liquiritin, isoliquiritin, liquiritigenin, liquiritin apioside, isoliquiritin apioside were increased 20.16%,45.31%,53.56%,27.66%,23.54%,8.46% with the 0.7 mg•L⁻¹ BR stimulating 2 months later. The best effects were achieved in 2 months after brassinolide stimulating. The conclusions prove that morphological characters and the main chemical constituents accumulation of G. uralensis could be effected by exogenous BR stimulation in certain case.

Effect of exogenous brassinolide on morphological characters and contents of seven chemical constituents of Glycyrrhiza uralensis / 中国中药杂志

The transplants of the two-year-old Glycyrrhiza uralensis were subjected to four concentration of brassinolide (BR 0.1, 0.4, 0.7, 1.0 mg•L⁻¹) in July. The morphological characters ( plant height, stem diameter, nodes number, internode length and root length , root thick, root fresh weight and root dry weight ) were measured and seven kinds of chemical constituents (glycyrrhizic acid, liquiritin, isoliquiritin, liquiritigenin, isoliquiritigenin, liquiritin apioside, isoliquiritin apioside) were determined by HPLC with the aim of increasing sinter output and improving quality of G. uralensis. Then the long-term dynamic changes of these morphological characters and chemical compositions' content were analyzed. The results showed that morphological characters of plant height, stem diameter, root length , root thick, root fresh weight and root dry weight increased remarkably with the 0.7 mg•L⁻¹ BR stimulating 2 months later,the increase rates were： 15.09%,6.15%,16.52%,8.46%,21.90%,29.41%, respectively. The content of glycyrrhizic acid, liquiritin, isoliquiritin, liquiritigenin, liquiritin apioside, isoliquiritin apioside were increased 20.16%,45.31%,53.56%,27.66%,23.54%,8.46% with the 0.7 mg•L⁻¹ BR stimulating 2 months later. The best effects were achieved in 2 months after brassinolide stimulating. The conclusions prove that morphological characters and the main chemical constituents accumulation of G. uralensis could be effected by exogenous BR stimulation in certain case.