Transcriptome analysis provides insights into lignin synthesis and MAPK signaling pathway that strengthen the resistance of bitter gourd (Momordica charantia) to Fusarium wilt

Metabolome Revealed the Potential Mechanism of Fusarium Wilt Resistance in Bitter Gourd (Momordica charantia) Based on Liquid Chromatography with Mass Spectrometry

Fusarium wilt fungus infection of bitter gourd, a major melon vegetable crop, results in massive yield reduction. Through extensive testing, some Fusarium wilt-resistant bitter melon varieties have been produced, but the molecular mechanism of their resistance to the fungus remains unknown. Importantly, after bitter melon plants are infected with Fusarium oxysporum f. sp. momordicae (FOM), apart from altering their gene expression levels, numerous metabolites are produced because of the interaction with the fungus. In the current study, an untargeted metabolomics analysis was performed to investigate the metabolic difference between resistant and susceptible bitter gourd varieties at various timepoints postinoculation with FOM based on liquid chromatography with mass spectrometry. A total of 1,595 positive ion mode and 922 negative ion mode metabolites were identified. Between the resistant and susceptible bitter gourd varieties, 213 unique differentially abundant metabolites (DAMs) were identified, and they were mainly enriched in the alpha-linolenic acid metabolism pathway. By comparing the postinoculation with preinoculation timepoints in the resistant and susceptible bitter gourd varieties, 93 and 159 DAMs were identified, respectively. These DAMs were mainly related to beta-alanine metabolism, among others. Multiple metabolites in the biosynthesis of the phenylpropanoid pathway showed greater variability in the susceptible than the resistant varieties, which may be related to senescence and mortality in the susceptible variety. These results provide new insights into the understanding of metabolite changes after FOM infection and a theoretical foundation for the elucidation of the bitter gourd disease resistance mechanism.

Transcriptomic and metabolomic analyses reveals keys genes and metabolic pathways in tea (Camellia sinensis) against six-spotted spider mite (Eotetranychus Sexmaculatus)

BACKGROUND

Six-spotted spider mite (Eotetranychus sexmaculatus) is one of the most damaging pests of tea (Camellia sinensis). E. sexmaculatus causes great economic loss and affects tea quality adversely. In response to pests, such as spider mites, tea plants have evolved resistance mechanisms, such as expression of defense-related genes and defense-related metabolites.

RESULTS

To evaluate the biochemical and molecular mechanisms of resistance in C. sinensis against spider mites, "Tianfu-5" (resistant to E. sexmaculatus) and "Fuding Dabai" (susceptible to E. sexmaculatus) were inoculated with spider mites. Transcriptomics and metabolomics based on RNA-Seq and liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) technology were used to analyze changes in gene expression and metabolite content, respectively. RNA-Seq data analysis revealed that 246 to 3,986 differentially expressed genes (DEGs) were identified in multiple compared groups, and these DEGs were significantly enriched in various pathways, such as phenylpropanoid and flavonoid biosynthesis, plant-pathogen interactions, MAPK signaling, and plant hormone signaling. Additionally, the metabolome data detected 2,220 metabolites, with 194 to 260 differentially abundant metabolites (DAMs) identified in multiple compared groups, including phenylalanine, lignin, salicylic acid, and jasmonic acid. The combined analysis of RNA-Seq and metabolomic data indicated that phenylpropanoid and flavonoid biosynthesis, MAPK signaling, and Ca2+-mediated PR-1 signaling pathways may contribute to spider mite resistance.

CONCLUSIONS

Our findings provide insights for identifying insect-induced genes and metabolites and form a basis for studies on mechanisms of host defense against spider mites in C. sinensis. The candidate genes and metabolites identified will be a valuable resource for tea breeding in response to biotic stress.