Co-expression of GbMYB1 and GbMYC1 induces anthocyanin accumulation in roots of cultured Gynura bicolor DC. plantlet on methyl jasmonate treatment

Advances in functional studies of plant MYC transcription factors

Myelocytomatosis (MYC) transcription factors (TFs) belong to the basic helix-loop-helix (bHLH) family in plants and play a central role in governing a wide range of physiological processes. These processes encompass plant growth, development, adaptation to biotic and abiotic stresses, as well as secondary metabolism. In recent decades, significant strides have been made in comprehending the multifaceted regulatory functions of MYCs. This advancement has been achieved through the cloning of MYCs and the characterization of plants with MYC deficiencies or overexpression, employing comprehensive genome-wide 'omics' and protein-protein interaction technologies. MYCs act as pivotal components in integrating signals from various phytohormones' transcriptional regulators to orchestrate genome-wide transcriptional reprogramming. In this review, we have compiled current research on the role of MYCs as molecular switches that modulate signal transduction pathways mediated by phytohormones and phytochromes. This comprehensive overview allows us to address lingering questions regarding the interplay of signals in response to environmental cues and developmental shift. It also sheds light on the potential implications for enhancing plant resistance to diverse biotic and abiotic stresses through genetic improvements achieved by plant breeding and synthetic biology efforts.

Combined application of sucrose and 1-MCP alleviated the senescence of Gynura bicolor DC through regulating hexose accumulation

As a leaf vegetable, Gynura bicolor DC (G. bicolor) experiences a rapid deterioration after harvest including insufficient supply of sugar and destruction of cell membranes. In this research, four treatments were experimented on G. bicolor including the control (CK), 12% (g/g) sucrose (ST), 10 μL L-1 1-MCP (MT), and the combination of sucrose and 1-MCP (SMT). The results showed that three treated groups reduced respiratory rate, inhibited hexose consumption and promoted the decrease of starch and sucrose, which was converted into hexose including glucose and fructose to maintain cell membrane integrity. Meanwhile, the activities of AI, NI, SS-C, amylase, and corresponding gene expression levels were significantly up-regulated in three treated groups at 1 d, among which AI played a crucial role in regulating the accumulation of hexose. Furthermore, ST exerted a pronounced effect on hexose accumulation at the beginning while MT reduced hexose consumption through lowered respiratory metabolism during storage. Notably, SMT exhibited an optimum preservation effect on inhibited respiratory metabolism, maintaining cell membrane integrity, enhancing the retention of hexose, indicating that a synergistic effect of ST and MT were developed during storage.

Effect of postharvest 1-methylcyclopropene application on reactive oxygen species scavenging and sucrose metabolism in Gynura bicolor DC

After harvest, the metabolism of Gynura bicolor DC (G. bicolor) is vigorous, resulting in sugar scarcity and reactive oxygen species (ROS) accumulation, thus aggravating the quality deterioration. 1-Methylcyclopropene (1-MCP) shows crucial effect in alleviating the postharvest metabolism of vegetables and fruits. This research aimed to evaluate the effect of 1-MCP on ROS scavenging and sucrose metabolism in G. bicolor. In this research, G. bicolor was treated with 10 μL L^-1 1-MCP for 12 h, followed by storage at 20 ± 2 °C and 90 ± 5% relative humidity in darkness for 7 days. During storage, the increases in the respiration rate, electrolytic leakage, weight loss rate, ROS levels, and membrane lipid oxidation were effectively inhibited by 1-MCP. Moreover, starch and hexose degradation was decreased in the 1-MCP group, as were sucrose synthesis and catabolism. Correlation analysis indicated that sugar starvation was associated with respiration, activities regulation of CAT, SOD, and enzymes involved in sucrose metabolism were associated with the levels of hydrogen peroxide at the early storage. In conclusion, 1-MCP delayed postharvest quality deterioration of G. bicolor by alleviating respiration, inducing oxidative stress to enhance ROS scavenging, and inhibiting sucrose metabolism.

AcMYB1 Interacts With AcbHLH1 to Regulate Anthocyanin Biosynthesis in Aglaonema commutatum

Aglaonema commutatum is one of the most popular foliage plants with abundant leaf phenotypes; therefore, anthocyanin coloration is a vital economic trait in A. commutatum. However, the molecular mechanisms underlying anthocyanin biosynthesis and its regulation remain unclear. In this study, AcMYB1 and AcbHLH1, transcription factor genes related to an R2R3-myeloblast (MYB) and a basic helix-loop-helix (bHLH), respectively, were isolated from A. commutatum "Red Valentine" and functionally characterized. AcMYB1 and AcbHLH1 were found to interact by Y2H and BiFC assay. AcMYB1 was grouped into the AN2 subgroup and shared high homology with the known regulators of anthocyanin biosynthesis. Gene expression analysis showed that both AcMYB1 and AcbHLH1 have similar expression patterns to anthocyanin structural genes and correlate with anthocyanin distribution in different tissues of A. commutatum. Light strongly promoted anthocyanin accumulation by upregulating the expression of anthocyanin-related genes in A. commutatum leaves. Ectopic expression of AcMYB1 in tobacco remarkably increased anthocyanin accumulation in both vegetative and reproductive tissues at various developmental stages. These results provide insights into the regulation of anthocyanin biosynthesis in A. commutatum and are useful for breeding new A. commutatum cultivars with enhanced ornamental value.

The basic helix-loop-helix transcription factor TabHLH1 increases chlorogenic acid and luteolin biosynthesis in Taraxacum antungense Kitag

Polyphenols are the main active components of the anti-inflammatory compounds in dandelion, and chlorogenic acid (CGA) is one of the primary polyphenols. However, the molecular mechanism underlying the transcriptional regulation of CGA biosynthesis remains unclear. Hydroxycinnamoyl-CoA:quinate hydroxycinnamoyl transferase (HQT2) is the last rate-limiting enzyme in chlorogenic acid biosynthesis in Taraxacum antungense. Therefore, using the TaHQT2 gene promoter as a probe, a yeast one-hybrid library was performed, and a basic helix-loop-helix (bHLH) transcription factor, TabHLH1, was identified that shared substantial homology with Gynura bicolor DC bHLH1. The TabHLH1 transcript was highly induced by salt stress, and the TabHLH1 protein was localized in the nucleus. CGA and luteolin concentrations in TabHLH1-overexpression transgenic lines were significantly higher than those in the wild type, while CGA and luteolin concentrations in TabHLH1-RNA interference (RNAi) transgenic lines were significantly lower. Quantitative real-time polymerase chain reaction demonstrated that overexpression and RNAi of TabHLH1 in T. antungense significantly affected CGA and luteolin concentrations by upregulating or downregulating CGA and luteolin biosynthesis pathway genes, especially TaHQT2, 4-coumarate-CoA ligase (Ta4CL), chalcone isomerase (TaCHI), and flavonoid-3'-hydroxylase (TaF3'H). Dual-luciferase, yeast one-hybrid, and electrophoretic mobility shift assays indicated that TabHLH1 directly bound to the bHLH-binding motifs of proTaHQT2 and proTa4CL. This study suggests that TabHLH1 participates in the regulatory network of CGA and luteolin biosynthesis in T. antungense and might be useful for metabolic engineering to promote plant polyphenol biosynthesis.

Integrated metabolomics and transcriptome analysis on flavonoid biosynthesis in safflower (Carthamus tinctorius L.) under MeJA treatment

BACKGROUND

Safflower (Carthamus tinctorius L.) is an important cash crop, of which the dried tube flower is not only an important raw material for dyes and cosmetics but also an important herb widely used in traditional Chinese medicine. The pigment and bioactive compounds are composed of flavonoids (mainly quinone chalcones), and studies have reported that MeJA can promote the biosynthesis of quinone chalcones, but the mechanism underlying the effect of MeJA in safflower remains unclear. Here, we attempt to use metabolomics and transcriptome technologies to analyse the molecular mechanism of flavonoid biosynthesis under MeJA treatment in safflower.

RESULTS

Based on a UHPLC-ESI-MS/MS detection platform and a self-built database (including hydroxysafflor yellow A, HSYA), a total of 209 flavonoid metabolites were detected, and 35 metabolites were significantly different after treatment with MeJA. Among them, 24 metabolites were upregulated upon MeJA treatment, especially HSYA. Eleven metabolites were downregulated after MeJA treatment. Integrated metabolomics and transcriptome analysis showed that MeJA might upregulate the expression of upstream genes in the flavonoid biosynthesis pathway (such as CHSs, CHIs and HCTs) and downregulate the expression of downstream genes (such as F3Ms, ANRs and ANSs), thus promoting the biosynthesis of quinone chalcones, such as HSYA. The transcription expressions of these genes were validated by real-time PCR. In addition, the promoters of two genes (CtCHI and CtHCT) that were significantly upregulated under MeJA treatment were cloned and analysed. 7 and 3 MeJA response elements were found in the promoters, respectively.

CONCLUSIONS

MeJA might upregulate the expression of the upstream genes in the flavonoid biosynthesis pathway and downregulate the expression of the downstream genes, thus promoting the biosynthesis of quinone chalcones. Our results provide insights and basic data for the molecular mechanism analysis of flavonoid synthesis in safflower under MeJA treatment.

Upland Italian Potato Quality—A Perspective

Upland potatoes satisfies consumer demand for high quality foods linked to traditional areas of origin and for new specialties and niche products endowed with added nutritional value, as it is commonly thought that the crop and environment synergy improves the potential beneficial properties of the tuber and gives it a special taste and a renowned quality. Herein, we report considerations on Italian germplasm and the effect of altitude on the sensorial and nutritional value of potato tubers, and investigate the possibility of addressing the nutritional challenge through mountain, eco-friendly, and social agriculture. Finally, we discuss the molecular and biochemical results concerning the impact of altitude on the compositional quality of the tuber, in order to justify promotional claims.

Phytochemical profile, antioxidative and anti-inflammatory potentials of Gynura bicolor DC

BACKGROUND

The phytochemical composition of aqueous and ethanol extracts from Gynura bicolor DC., a vegetable, was determined. Human umbilical vein endothelial (HUVE) cells were used to examine the antioxidative and anti-inflammatory potentials of these extracts at 1, 2 or 4% (v/v) against high-glucose-induced injury.

RESULTS

Both aqueous and ethanol extracts contained phenolic acids, flavonoids, carotenoids and anthocyanins in the ranges 1428-1569, 1934-2175, 921-1007 and 2135-2407 mg per 100 g dry weight respectively. Both extracts were rich in quercetin, lutein, malvidin and pelargonidin. Addition of these extracts at test doses decreased reactive oxygen species formation, preserved glutathione content and retained glutathione peroxide and catalase activities in high-glucose-treated HUVE cells (P < 0.05). Treatments with these extracts at 2 and 4% lowered interleukin-6, tumor necrosis factor-alpha and prostaglandin E2 production and reduced cyclooxygenase-2 activity (P < 0.05).

CONCLUSION

These findings suggest that this vegetable could be considered as a functional food and might provide antioxidative and anti-inflammatory protection.