The role of phytochromes in regulating biosynthesis of sterol glycoalkaloid in eggplant leaves

Transcription factors SlNOR and SlNOR-like1 regulate steroidal glycoalkaloids biosynthesis in tomato fruit

Steroidal glycoalkaloids (SGAs) are specialized metabolites in Solanaceae that serve as defensive compounds and undergo significant compositional changes during fruit ripening. This study explored the roles of transcription factors SlNOR and SlNOR-like1 in SGAs biosynthesis during tomato fruit development. UPLC-MS/MS revealed dynamic changes in four major SGAs: tomatidine, β-tomatine, α-tomatine, and Esculeoside A. Transgenic studies with knockout and overexpression lines demonstrated that both SlNOR and SlNOR-like1 positively regulated SGAs accumulation. RT-qPCR analysis showed that these transcription factors modulated multiple GAME genes in the SGAs biosynthetic pathway. Through EMSA and DLR assays, we established that SlNOR and SlNOR-like1 directly bound to and activated GAME25 and GAME40 promoters, two key genes involved in tomatidine synthesis and α-tomatine conversion, respectively. These findings reveal a previously unknown regulatory mechanism of SGAs metabolism and suggest potential strategies for optimizing tomato fruit quality through molecular breeding.

Structural Impact of Steroidal Glycoalkaloids: Barrier Integrity, Permeability, Metabolism, and Uptake in Intestinal Cells

SCOPE

Potato tubers represent an essential food component all over the world and an important supplier of carbohydrates, fiber, and valuable proteins. However, besides their health promoting effects, potatoes contain α-solanine and α-chaconine, which are toxic steroidal glycoalkaloids (SGAs). Other solanaceous plants like eggplants and tomatoes produce SGAs as well, different in their chemical structure. This study aims to investigate toxic effects (cholinesterase inhibition, membrane, and barrier disruption), permeability, metabolism, and structure-activity relationships of SGAs.

METHODS AND RESULTS

α-solanine, α-chaconine, α-solasonine, α-solamargine, α-tomatine, and their respective aglycones solanidine, solasodine, and tomatidine are analyzed using Ellman assay, cellular impedance spectroscopy, cell extraction, and Caco-2 intestinal model. Additionally, metabolism is analyzed by HPLC-MS techniques. The study observes dependencies of barrier disrupting potential and cellular uptake on the carbohydrate moiety of SGAs, while permeability and acetylcholinesterase (AChE) inhibition are dominated by the steroid backbone. SGAs show low permeabilities across Caco-2 monolayers in subtoxic concentrations. In contrast, their respective aglycones reveal higher permeabilities, but are extensively metabolized.

CONCLUSION

Besides structure-activity relationships, this study provides new information on the overall effects of steroidal alkaloids on intestinal cells and closes a gap of knowledge for the metabolic pathway from oral uptake to final excretion.

Integrated Transcriptome and Metabolome Analysis to Identify Sugarcane Gene Defense against Fall Armyworm (Spodoptera frugiperda) Herbivory

Sugarcane is the most important sugar crop, contributing ≥80% to total sugar production around the world. Spodoptera frugiperda is one of the main pests of sugarcane, potentially causing severe yield and sugar loss. The identification of key defense factors against S. frugiperda herbivory can provide targets for improving sugarcane resistance to insect pests by molecular breeding. In this work, we used one of the main sugarcane pests, S. frugiperda, as the tested insect to attack sugarcane. Integrated transcriptome and metabolomic analyses were performed to explore the changes in gene expression and metabolic processes that occurred in sugarcane leaf after continuous herbivory by S. frugiperda larvae for 72 h. The transcriptome analysis demonstrated that sugarcane pest herbivory enhanced several herbivory-induced responses, including carbohydrate metabolism, secondary metabolites and amino acid metabolism, plant hormone signaling transduction, pathogen responses, and transcription factors. Further metabolome analysis verified the inducement of specific metabolites of amino acids and secondary metabolites by insect herbivory. Finally, association analysis of the transcriptome and metabolome by the Pearson correlation coefficient method brought into focus the target defense genes against insect herbivory in sugarcane. These genes include amidase and lipoxygenase in amino acid metabolism, peroxidase in phenylpropanoid biosynthesis, and pathogenesis-related protein 1 in plant hormone signal transduction. A putative regulatory model was proposed to illustrate the sugarcane defense mechanism against insect attack. This work will accelerate the dissection of the mechanism underlying insect herbivory in sugarcane and provide targets for improving sugarcane variety resistance to insect herbivory by molecular breeding.

He-Ne laser accelerates seed germination by modulating growth hormones and reprogramming metabolism in brinjal

A plant’s ability to maximize seed germination, growth, and photosynthetic productivity depends on its aptitude to sense, evaluate, and respond to the quality, quantity, and direction of the light. Among diverse colors of light possessing different wavelengths and red light shown to have a high impact on the photosynthetic and growth responses of the plants. The use of artificial light sources where the quality, intensity, and duration of exposure can be controlled would be an efficient method to increase the efficiency of the crop plants. The coherent, collimated, and monochromatic properties of laser light sources enabled as biostimulator compared to the normal light. The present study was attempted to use the potential role of the He–Ne laser as a bio-stimulator device to improve the germination and growth of brinjal and to investigate the possible interactions of plant and laser photons. A substantial enhancement was observed in germination index, germination time and seed vigor index of laser-irradiated than control groups. The enhanced germination rate was correlated with higher GA content and its biosynthetic genes whereas decreased ABA content and its catabolic genes and GA/ABA ratio were noted in laser-irradiated groups during seed germination than control groups. Further the expression of phytochrome gene transcripts, PhyA and PhyB1 were upregulated in laser-irradiated seedlings which correlate with enhanced seed germination than control. Elevated levels of primary metabolites were noted in the early stages of germination whereas modulation of secondary metabolites was observed in later growth. Consequently, significantly increased photosynthetic rate, stomatal conductance, and transpiration rate was perceived in laser-irradiated seedlings compare with control. The current study showed hormone and phytochrome-mediated mechanisms of seed germination in laser-irradiated groups along with the enhanced photosynthetic rate, primary and secondary metabolites.

Solanum steroidal glycoalkaloids: structural diversity, biological activities, and biosynthesis

Chemical structures of typical Solanum steroidal glycoalkaloids from eggplant, tomato, and potato.

Identification of WRKY gene family and characterization of cold stress-responsive WRKY genes in eggplant

BACKGROUND

WRKY proteins play a vital role in the plants response to different stresses, growth and development. Studies of WRKY proteins have been mainly focused on model plant Arabidopsis and a few other vegetable plants. However, the systematical study of eggplant WRKY transcription factor superfamily is scarce.

METHODS

Bioinformatics has been used to identify and characterize the eggplant WRKY gene family. For the exploration of the differentially expressed WRKY genes, two cultivars with different cold-tolerance were used. Finally, we performed a virus-induced gene silencing (VIGS) experiment to verify the functions of SmWRKY26 and SmWRKY32.

RESULTS

Fifty eight (58) genes encoding eggplant WRKY proteins were identified through searching the eggplant genome. Eggplant WRKY proteins could be classified into three groups or seven subgroups in accordance with other plants. WRKY variants were identified from the eggplant. Gene structure analysis showed that the number of intron in eggplant WRKY family was from 0 to 11, with an average of 4.4. Conserved motif analysis suggested that WRKY DNA-binding domain was conserved in eggplant WRKY proteins. Furthermore, RNA-seq data showed that WRKY genes were differentially expressed in eggplant response to cold stress. By using VIGS, the two differentially expressed genes-SmWRKY26 and SmWRKY32 were verified in response to cold stress.

DISCUSSIONS

This study provides a foundation for further exploring the functions of WRKY proteins in eggplant response to stresses and eggplant genetic improvement in stresses.

Oviposition by Spodoptera exigua on Solanum dulcamara Alters the Plant's Response to Herbivory and Impairs Larval Performance

Plant resistance traits against insect herbivores are extremely plastic. Plants respond not only to the herbivory itself, but also to oviposition by herbivorous insects. How prior oviposition affects plant responses to larval herbivory is largely unknown. Combining bioassays and defense protein activity assays with microarray analyses and metabolite profiling, we investigated the impact of preceding oviposition on the interaction of Solanum dulcamara with the generalist lepidopteran herbivore Spodoptera exigua at the levels of the plant’s resistance, transcriptome and metabolome. We found that oviposition increased plant resistance to the subsequent feeding larvae. While constitutive and feeding-induced levels of defensive protease inhibitor activity remained unaffected, pre-exposure to eggs altered S. dulcamara’s transcriptional and metabolic response to larval feeding in leaves local and systemic to oviposition. In particular, genes involved in phenylpropanoid metabolism were more strongly expressed in previously oviposited plants, which was reflected by reciprocal changes of primary metabolites upstream and within these pathways. Our data highlight that plants integrate signals from non-threatening life stages of their natural enemies to optimize their response when they become actually attacked. The observed transcriptional and metabolic reshaping of S. dulcamara’s response to S. exigua herbivory suggests a role of phenylpropanoids in oviposition-primed plant resistance.