Junheng Lv

Pepper is an important vegetable and widely cultivated across the world. Anthocyanins play a crucial role in determining the color and nutritional value of pepper. In this study, light effects on anthocyanins accumulation in purple peppers were analyzed via bagging and non-bagging treatments. Transcription factor CaWRKY44 was identified as playing a key role in anthocyanins synthesis according to the metabolome and transcriptome analysis. CaWRKY44 expression increased during the different pepper pericarp developmental stages and a promoter cis-element analysis identified light and hormone-responsive elements and protein-binding motifs. VIGS-mediated silencing of CaWRKY44 reduced anthocyanins accumulation, while transient overexpression enhanced pigment deposition. Furthermore, the silencing or overexpression of CaWRKY44 modulated the expression level of anthocyanins biosynthetic structural genes. Our results indicated that CaWRKY44 could directly bind to the W-box cis-element in the CaDFR promoter and activates its transcription, which subsequently drives anthocyanins biosynthesis. The results could lay the foundation of the regulatory mechanism controlling anthocyanins biosynthesis in pepper. The online version contains supplementary material available at 10.1186/s12870-026-08691-8.

The bHLH transcription factors play a crucial regulatory role in plant growth and development. In this study, the CcbHLH68 gene was cloned from the pepper cultivar ‘Shuanla’. Subsequent bioinformatics analysis, subcellular localization, expression pattern profiling, along with yeast one-hybrid and dual-luciferase reporter assays, were conducted to preliminarily elucidate its regulatory mechanism in capsaicinoid biosynthesis. The results revealed that the visualization of upstream cis-elements of CcbHLH68 suggests its potential regulation by hormones. Furthermore, subcellular localization experiments confirmed that the CcbHLH68 protein is localized in the nucleus. Expression analysis of CcbHLH68 across different tissues by qRT-PCR identified its predominant expression in the placenta at 30 days post-anthesis. Further experimental evidence from both gene silencing and transient overexpression assays demonstrated a positive correlation between CcbHLH68 and the expression of multiple capsaicinoid biosynthetic genes. When it was silenced or transiently overexpressed, the content of capsaicinoids decreased by 40.9% or increased by 113.7%, respectively. Yeast one-hybrid and dual-luciferase reporter assays confirmed that CcbHLH68 can directly bind to the CcCOMT promoter and activate its transcription. In summary, this study preliminarily reveals the molecular mechanism by which CcbHLH68 participates in capsaicinoid biosynthesis through regulating the expression of key genes in the biosynthetic pathway, thereby providing a theoretical foundation for enhancing capsaicinoid content via molecular breeding.

Pepper is a fruit, vegetable, and spice crop and is widely cultivated around the world. This study analyzed the transcriptomes and metabolomes of pepper fr

The MADS-box transcription factor family is involved in regulating plant root germination, flowering, fruit development, maturation, and the biosynthesis of secondary metabolites. To investigate the role of MADS-box transcription factors in anthocyanin biosynthesis, this study utilized the pepper cultivar ‘CS03’ as experimental material. A transcription factor, CaMADS1, was selected from our previous transcriptome data for cloning and bioinformatic analysis. The results revealed that the CaMADS1 protein is localized to the nucleus. Quantitative real-time PCR analysis demonstrated that CaMADS1 is predominantly expressed in leaves. In CaMADS1-silenced plants, anthocyanin accumulation in the leaves decreased, which was consistent with the downregulated expression of structural genes in the biosynthesis pathway. In CaMADS1-overexpressing plants, both anthocyanin accumulation and the expression of these structural genes were elevated. Yeast one-hybrid and Dual-luciferase assays confirmed the interaction between CaMADS1 and the promoter of CaC4H, which encodes a key enzyme in anthocyanin biosynthesis. These results demonstrate that CaMADS1 positively regulates anthocyanin biosynthesis in pepper by directly binding to the promoter of the CaC4H gene.

Pepper is an important vegetable and economic crop, and the MYB family is one of the most numerous transcription factor families in plants, extensively participating in various biological processes such as plant growth, development, and stress resistance. In this study, CcMYB330 is identified as a differentially expressed gene in the pepper fruit, and CcMYB330 is expressed with higher expression levels in the placenta and pericarp at different development stages of pepper fruit. Analysis of the promoter cis-elements revealed that this gene contains not only core elements but also environmental factor response elements and plant hormone response elements. The silencing of CcMYB330 could reduce the capsaicinoid accumulation in pepper fruit, while the overexpression of CcMYB330 could increase capsaicinoid accumulation. Additionally, silencing or overexpressing CcMYB330 could regulate the expression of structural genes involved in capsaicinoid biosynthesis. In addition, through yeast one-hybrid experiments, we identified an interaction between CcMYB330 and the capsaicinoid biosynthesis structural gene CcPAL. Further evidence from EMSA experiments and dual luciferase assays confirmed that CcMYB330 can bind to the cis-element ACCAACAACCAAA in the CcPAL promoter. These results indicate that CcMYB330 may regulate the synthesis of capsaicinoids by modulating structural genes in the capsaicinoid biosynthesis pathway, providing new insights into the regulatory mechanisms of capsaicinoid synthesis.

Background: Millet peppers have rich and diverse germplasm resources. It is of great significance to characterize their phenotypes and physicochemical indicators. Methods: 30 millet germplasms were selected to measure the fruit length and width, flesh thickness, number of ventricles, fruit stalk length, and single fruit weight, and the texture characteristics of fruit such as hardness, cohesiveness, springiness, gumminess, and chewiness were determined by a texture analyzer. At the same time, high-performance liquid chromatography (HPLC) and gas chromatography (GC) were used to determine the fruit of capsaicin, dihydrocapsaicin, nordihydrocapsaicin, fatty acids, vitamin E (VE), total phenol, total sugar, and total dietary fiber. Results: M11 showed outstanding parameters in phenotype and texture. The coefficient of variation (CV) for VE was as high as 94.943% and the highest diversity index (H’) was total soluble solid, at 1.988%. M5 and M18 contained rich and diverse fatty acids. At the same time, the content of capsaicinoids in M18 also ranks among the top, second only to M27 (with a total capsaicin content of 5623.96 μg/g). PCA analysis using phenotypic data and physicochemical data showed that the classification results were different. Further hierarchical group analysis was carried out using all the index data. The results showed that 30 millet pepper germplasms were divided into three new categories: M5, M9, M18, and M24 formed one group (C1), M10, M14, M16, M19, M20, M22, M25, M26, M28, M29, and M30 formed another cluster (C2), and the remaining germplasms formed a third cluster (C3). Among them, the abundance of fatty acids in the C1 germplasm was higher than that in the other two groups. Conclusions: Our study showed that different germplasms had significant differences in morphological traits and nutritional metabolic components and were rich in genetic diversity. This study provides a theoretical basis for the improvement of millet varieties and the development of functional food.

Anthocyanins are important flavonoid compounds in plants that are associated with the color formation and antioxidant activity of flowers, fruits, and other organs. Ultraviolet B radiation (UV-B) is one of the key environmental factors that influence anthocyanin accumulation in plants and HY5 is involved in plant photomorphogenesis. However, the molecular mechanism of the signal network of UV-B regulating anthocyanin biosynthesis in capsicum via HY5 remains unclear. In this study, we identified the transcription factor CaHY5, which mediates UV-B signaling, and demonstrated its regulatory role in anthocyanin biosynthesis in purple pepper (Capsicum annuum L.). The results showed that there were photoresponsive and hormone-responsive elements on the CaHY5 promoter that responded to UV-B, indoleacetic acid, salicylic acid, 6-benzyladenine, abscisic acid, and melatonin treatments. UV-B treatment induced the expression of CaHY5 and anthocyanin structural genes. CaHY5 gene-silenced positive plants showed different degrees of the yellowing phenomenon, which affected the expression of the anthocyanin biosynthesis structural gene. The expression levels of anthocyanin biosynthesis-related genes in CaHY5-silenced positive plants increased considerably. This study provides insights into the role of CaHY5 in UV-B-induced anthocyanin biosynthesis in purple pepper.

In the post-genomic era, virus-induced gene silencing (VIGS) has played an important role in research on reverse genetics in plants. Commonly used Agrobacterium-mediated VIGS inoculation methods include stem scratching, leaf infiltration, use of agrodrench, and air-brush spraying. In this study, we developed a root wounding–immersion method in which 1/3 of the plant root (length) was cut and immersed in a tobacco rattle virus (TRV)1:TRV2 mixed solution for 30 min. We optimized the procedure in Nicotiana benthamiana and successfully silenced N. benthamiana, tomato (Solanum lycopersicum), pepper (Capsicum annuum L.), eggplant (Solanum melongena), and Arabidopsis thaliana phytoene desaturase (PDS), and we observed the movement of green fluorescent protein (GFP) from the roots to the stem and leaves. The silencing rate of PDS in N. benthamiana and tomato was 95–100%. In addition, we successfully silenced two disease-resistance genes, SITL5 and SITL6, to decrease disease resistance in tomatoes (CLN2037E). The root wounding–immersion method can be used to inoculate large batches of plants in a short time and with high efficiency, and fresh bacterial infusions can be reused several times. The most important aspect of the root wounding–immersion method is its application to plant species susceptible to root inoculation, as well as its ability to inoculate seedlings from early growth stages. This method offers a means to conduct large-scale functional genome screening in plants.