Linking environmental signals to plant metabolism: The combination of field trials and environment simulators

Short-term high-light intensity and low temperature improve the quality and flavor of lettuce grown in plant factory

BACKGROUND

Lettuce holds a prominent position in the year-round supply of vegetables, offering a rich array of health-beneficial substances, such as dietary fiber, phenolic compounds, lactucopicrin and lactucin. As such, its flavor has garnered increasing attention. Balancing the enhancement of beneficial compounds with the reduction of undesirable taste is a key focus of scientific research. To investigate short-term management to improve the nutritional quality and flavor of lettuce, combinations of different light intensities (200, 500 and 800 μm ol m-2 s-1) and temperatures (10 and 22 °C) were applied separately to 'Lollo Rosso' and 'Little Butter Lettuce' for 7 days before harvest.

RESULTS

The results obtained showed that increasing light intensity at low temperatures decreased nitrate content and increased soluble sugar, soluble protein, anthocyanin and phenolic compound content. In the case of lettuce flavor, the bitterness-related metabolites such as lactucin and lactucopicrin were reduced with high light intensity at a low temperature of 10 °C. With this combination, the fructose and glucose contents increased, significantly improving lettuce flavor.

CONCLUSION

Higher light intensity combined with low temperature for 7 days before harvest effectively improved the nutritional quality and flavor of lettuce, suggesting its great potential for use in horticultural practices. © 2024 Society of Chemical Industry.

Genome-wide characterization of the bHLH gene family in Gynostemma pentaphyllum reveals its potential role in the regulation of gypenoside biosynthesis

BACKGROUND

Gynostemma pentaphyllum, an ancient Chinese herbal medicine, serves as a natural source of gypenosides with significant medicinal properties. Basic helix-loop-helix (bHLH) transcription factors play pivotal roles in numerous biological processes, especially in the regulation of secondary metabolism in plants. However, the characteristics and functions of the bHLH genes in G. pentaphyllum remain unexplored, and their regulatory role in gypenoside biosynthesis remains poorly elucidated.

RESULTS

This study identified a total of 111 bHLH members in G. pentaphyllum (GpbHLHs), categorizing them into 26 subgroups based on shared conserved motif compositions and gene structures. Collinearity analysis illustrated that segmental duplications predominately lead to the evolution of GpbHLHs, with most duplicated GpbHLH gene pairs undergoing purifying selection. Among the nine gypenoside-related GpbHLH genes, two GpbHLHs (GpbHLH15 and GpbHLH58) were selected for further investigation based on co-expression analysis and functional prediction. The expression of these two selected GpbHLHs was dramatically induced by methyl jasmonate, and their nuclear localization was confirmed. Furthermore, yeast one-hybrid and dual-luciferase assays demonstrated that GpbHLH15 and GpbHLH58 could bind to the promoters of the gypenoside biosynthesis pathway genes, such as GpFPS1, GpSS1, and GpOSC1, and activate their promoter activity to varying degrees.

CONCLUSIONS

In conclusion, our findings provide a detailed analysis of the bHLH family and valuable insights into the potential use of GpbHLHs to enhance the accumulation of gypenosides in G. pentaphyllum.

Untargeted metabolomics in Anectocillus roxburghii with habitat heterogeneity and the key abiotic factors affecting its active ingredients

Introduction

Anoectochilus roxburghii is a rare, endangered herb with diverse pharmacological properties. Understanding the main metabolite types and characteristics of wild A. roxburghii is important for efficiently utilizing resources and examining quality according to origin.

Methods

Samples were collected from the main production areas across five regions in Fujian Province, China. An untargeted metabolomics analysis was performed on the entire plants to explore their metabolic profiles. We utilized UPLC-MS/MS to specifically quantify eight targeted flavonoids in these samples. Subsequently, correlation analysis was conducted to investigate the relationships between the flavonoids content and both the biological characteristics and geographical features.

Results

A comprehensive analysis identified a total of 3,170 differential metabolites, with terpenoids and flavonoids being the most prevalent classes. A region-specific metabolite analysis revealed that the Yongchun (YC) region showed the highest diversity of unique metabolites, including tangeretin and oleanolic acid. Conversely, the Youxi (YX) region was found to have the smallest number of unique metabolites, with only one distinct compound identified. Further investigation through KEGG pathway enrichment analysis highlighted a significant enrichment in pathways related to flavonoid biosynthesis. Further examination of the flavonoid category showed that flavonols were the most differentially abundant. We quantified eight specific flavonoids, finding that, on average, the YX region exhibited higher levels of these compounds. Correlation analysis highlighted a significant association between flavonoids and habitat, especially temperature and humidity.

Discussion

Untargeted metabolomics via LC-MS was suitable for identifying region-specific metabolites and their influence via habitat heterogeneity. The results of this study serve as a new theoretical reference for unique markers exclusively present in a specific sample group.

Effects of long-term blue light irradiation on carotenoid biosynthesis and antioxidant activities in Chinese cabbage (Brassica rapa L. ssp. pekinensis)

The aim of this study was to investigate the impact of long-term exposure to blue light-emitting diodes (LEDs) on the accumulation of indolic glucosinolates and carotenoids, as well as the plant growth and antioxidant activities in both orange and common Chinese cabbage (Brassica rapa L. ssp. pekinensis). Blue light treatment also induced higher ferric-reducing antioxidant power and 2,2-diphenyl-1-picrylhydrazyl by 20.66 % and 30.82 % and antioxidant enzyme activities catalase, peroxidase, superoxide dismutase, and the accumulation of non-enzymatic antioxidant substances (total phenols and total flavonoids) in the orange Chinese cabbage. Furthermore, long-term exposure to blue light had negative effects on the net photosynthetic rate and chlorophyll fluorescence levels. Meanwhile, blue light promoted accumulation of Indol-3-ylmethyl glucosinolate (I3M), β-carotene, lutein and zeaxanthin due to the high expression of regulatory and biosynthetic genes of the above metabolic pathways. In particular, lycopene and β-carotene content in orange Chinese cabbage increased by 60.14 % and 65.33 % compared to the ones in common line. The accumulation of carotenoid and increasing antioxidant levels in the orange cabbage line was influenced by long-term blue light irradiation, leading to better tolerance to low temperature and drought stresses. The up-regulation of transcription factors such as BrHY5-2, BrPIF4 and BrMYB12 may also contribute to the increased tolerance in orange Chinese cabbage to extreme environmental stresses. The BrHY5-2 gene could activate carotenoid biosynthetic genes and induce the accumulation of carotenoids. These findings suggested that long-term blue light irradiation could be a promising technique for increasing the nutrition value and enhancing tolerance to low temperature and drought stresses in Chinese cabbage.

Light plays a critical role in the accumulation of chlorogenic acid in Lonicera macranthoides Hand.-Mazz

Light has important effects on plant metabolism. However, the relationship between the chlorogenic acid (CGA) content and light in plants remains unclear. Here, we investigated the effects of shading treatment on gene expression and CGA content in Lonicera macranthoides Hand.-Mazz. (LM), a widely used medicinal plant. A total of 1891 differentially expressed genes (DEGs) were obtained in flower buds and 819 in leaves in response to light in shading treatment compared to the control sample by RNA-Seq. After shading treatment, the content of CGA in LM leaves decreased significantly by 1.78-fold, the carotenoid content increased, and the soluble sugar and starch contents significantly decreased. WGCNA and the expression of related genes verified by qRT‒PCR revealed that CGA synthesis pathway enzyme genes form a co-expression network with genes for carbohydrate synthesis, photosynthesis, light signalling elements, and transcription factor genes (TFs) that affect the accumulation of CGA. Through a virus-induced gene silencing (VIGS) system and CGA assay in Nicotiana benthamiana (NB), we determined that downregulation of NbHY5 expression decreased the CGA content in NB leaves. In this study, we found that light provides energy and material for the accumulation of CGA in LM, and light affects the expression of CGA accumulation-related genes. Our results show that different light intensities have multiple effects on leaves and flower buds in LM and are able to coregulate LmHY5 expression and CGA synthesis.

Insights into accumulation of active ingredients and rhizosphere microorganisms between Salvia miltiorrhiza and S. castanea

Salvia miltiorrhiza is an important traditional herbal medicine, and its extracts could be used for treating cardiovascular disease. Although these medicinal compounds are functionally similar, their wild relative, S. castanea, produces significantly different concentrations of these compounds. The reason for their differences is still unknown. In a series of soil and plant-based analyses, we explored and compared the rhizosphere microbiome of S. miltiorrhiza and S. castanea. To further investigate the geographical distribution of S. castanea, MaxEnt models were used to predict the future suitable habitat areas of S. castanea in China. Results revealed the distributions and structure of the rhizosphere microbial community of S. miltiorrhiza and S. castanea at different times. In addition, differences in altitude and soil moisture resulting from changes in climate and geographical location are also critical environmental factors in the distribution of S. castanea. The findings of this study increase our understanding of plant adaptation to their geographical environment through secondary metabolites. It also highlights the complex interplay between rhizospheric factors and plant metabolism, which provides the theoretical basis for the cultivation of S. miltiorrhiza and the use of S. castanea resources.

Enrichment of health-promoting lutein and zeaxanthin in tomato fruit through metabolic engineering

Carotenoids constitute a large group of natural pigments widely distributed in nature. These compounds not only provide fruits and flowers with distinctive colors, but also have significant health benefits for humans. Lutein and zeaxanthin, both oxygen-containing carotenoids, are considered to play vital roles in promoting ocular development and maintaining eye health. However, humans and mammals cannot synthesize these carotenoid derivatives, which can only be taken from certain fruits or vegetables. Here, by introducing four endogenous synthetic genes, SlLCYE, SlLCYB, SlHYDB, and SlHYDE under fruit-specific promoters, we report the metabolic engineering of lutein/zeaxanthin biosynthesis in tomato fruit. Transgenic lines overexpression of one (SlLCYE), two (SlLCYE and SlLCYB; SlLCYB and SlHYDB), and all these four synthetic genes re-established the lutein/zeaxanthin biosynthetic pathways in the ripe tomato fruit and thus resulted in various types of carotenoid riched lines. Metabolic analyses of these engineered tomato fruits showed the strategy involved expression of SlLCYE tends to produce α-carotene and lutein, as well as a higher content of β-carotene and zeaxanthin was detected in lines overexpressing SlLCYB. In addition, the different combinations of engineered tomatoes with riched carotenoids showed higher antioxidant capacity and were associated with a significantly extended shelf life during postharvest storage. This work provides a successful example of accurate metabolic engineering in tomato fruit, suggesting the potential utility for synthetic biology to improve agronomic traits in crops. These biofortified tomato fruits could be also exploited as new research subjects for studying the health benefits of carotenoid derivatives.

Melatonin biosynthesis and signal transduction in plants in response to environmental conditions

Melatonin, the most widely distributed hormone in nature, plays important roles in plants. Many physiological processes in plants are linked to melatonin, including seed germination, anisotropic cell growth, and senescence. Compared with animals, different plants possess diverse melatonin biosynthetic pathways and regulatory networks. Whereas melatonin biosynthesis in animals is known to be regulated by ambient signals, little is known about how melatonin biosynthesis in plants responds to environmental signals. Plants are affected by numerous environmental factors, such as light, temperature, moisture, carbon dioxide, soil conditions, and nutrient availability at all stages of development and in different tissues. Melatonin content exhibits dynamic changes that affect plant growth and development. Melatonin plays various species-specific roles in plant responses to different environmental conditions. However, much remains to be learned, as not all environmental factors have been studied, and little is known about the mechanisms by which these factors influence melatonin biosynthesis. In this review, we provide a detailed, systematic description of melatonin biosynthesis and signaling and of the roles of melatonin in plant responses to different environmental factors, providing a reference for in-depth research on this important issue.

Transcriptome Analysis of Glutathione Response: RNA-Seq Provides Insights into Balance between Antioxidant Response and Glucosinolate Metabolism

When being stressed, plants require a balance between the resistance pathway and metabolism. Glucosinolates (GS) are secondary metabolics that widely exist in Brassicaceae. Glutathione (GSH) not only participates in plant processing reactive oxygen species (ROS) but also directly participates in GS synthesis as a sulfur donor. Therefore, we used transcriptomic to identify antioxidant and GS metabolism responses in GSH-treated pakchoi. Our study elucidated that GSH can be used as priming to improve oxidative resistance and preferentially stimulate the expression of resistance genes such as CAT1. The reduction in transcription factor expression inhibits the key steps of the GS synthesis pathway. When ROS returned to normal level, the resistance gene decreased and returned to normal level, while GSH restored the gene expression of GS biosynthesis. This work puts forward the mechanism of GSH in regulating the antioxidant system and glucosinolate metabolic pathway, which provides a basis for further study on the relationship between environmental signals and plant metabolism and provides ideas for follow-up research.

A review of approaches to control bacterial leaf blight in rice

The Gram-negative bacteria Xanthomonas oryzae pv. oryzae, the causative agent of bacterial leaf blight (BLB), received attention for being an economically damaging pathogen of rice worldwide. This damage prompted efforts to better understand the molecular mechanisms governing BLB disease progression. This research revealed numerous virulence factors that are employed by this vascular pathogen to invade the host, outcompete host defence mechanisms, and cause disease. In this review, we emphasize the virulence factors and molecular mechanisms that X. oryzae pv. oryzae uses to impair host defences, recent insights into the cellular and molecular mechanisms underlying host-pathogen interactions and components of pathogenicity, methods for developing X. oryzae pv. oryzae-resistant rice cultivars, strategies to mitigate disease outbreaks, and newly discovered genes and tools for disease management. We conclude that the implementation and application of cutting-edge technologies and tools are crucial to avoid yield losses from BLB and ensure food security.