6-Pentyl-2H-pyran-2-one from Trichoderma erinaceum Is Fungicidal against Litchi Downy Blight Pathogen Peronophythora litchii and Preservation of Litchi.

The postharvest losses of litchi caused by litchi downy blight are considerably high. We identified a natural antifungal volatile pyrone, 6-pentyl-2H-pyran-2-one (6PP), synthesized by Trichoderma erinaceum LS019-2 and investigated as biocontrol for litchi downy blight and preservation. 6PP significantly inhibited the growth and sporangial germination of Peronophythora litchii, the causal agent of litchi downy blight, and caused severe cellular and intracellular destructions, as evidenced by electron microscopic analysis. Furthermore, in the treatment, the fruit kept better color, higher weight, and antioxidant activity, so it can maintain freshness and prolong shelf life. Metabolome analysis confirmed the decline of lipids and the accumulation of organic acids in litchi fruits in response to 6PP treatment. These effects from 6PP could alleviate disease effects and prolong the shelf life of litchi fruits. These findings suggested that 6PP could be a useful natural product to control downy blight disease and a new preservative of litchi fruits.

A New Insight into 6-Pentyl-2H-pyran-2-one against Peronophythora litchii via TOR Pathway.

The litchi downy blight disease of litchi caused by Peronophythora litchii accounts for severe losses in the field and during storage. While ample quantitative studies have shown that 6-pentyl-2H-pyran-2-one (6PP) possesses antifungal activities against multiple plant pathogenic fungi, the regulatory mechanisms of 6PP-mediated inhibition of fungal pathogenesis and growth are still unknown. Here, we investigated the potential molecular targets of 6PP in the phytopathogenic oomycetes P. litchii through integrated deployment of RNA-sequencing, functional genetics, and biochemical techniques to investigate the regulatory effects of 6PP against P. litchii. Previously we demonstrated that 6PP exerted significant oomyticidal activities. Also, comparative transcriptomic evaluation of P. litchii strains treated with 6PP Revealed significant up-regulations in the expression profile of TOR pathway-related genes, including PlCytochrome C and the transcription factors PlYY1. We also noticed that 6PP treatment down-regulated putative negative regulatory genes of the TOR pathway, including PlSpm1 and PlrhoH12 in P. litchii. Protein-ligand binding analyses revealed stable affinities between PlYY1, PlCytochrome C, PlSpm1, PlrhoH12 proteins, and the 6PP ligand. Phenotypic characterization of PlYY1 targeted gene deletion strains generated in this study using CRISPR/Cas9 and homologous recombination strategies significantly reduced the vegetative growth, sporangium, encystment, zoospore release, and pathogenicity of P. litchii. These findings suggest that 6PP-mediated activation of PlYY1 expression positively regulates TOR-related responses and significantly influences vegetative growth and the virulence of P. litchii. The current investigations revealed novel targets for 6PP and underscored the potential of deploying 6PP in developing management strategies for controlling the litchi downy blight pathogen.

Comparative Genomic-Based Study of Reproduction-Related Genes in Three Fruit Fly Species.

Zeugodacus cucurbitae (Coquillett), Bactrocera dorsalis (Hendel), and Ceratitis capitata (Wiedemann) are important pests of fruit and vegetable crops and are difficult to control because of their rapid reproduction rate and egg production. To investigate the key genes regulating reproduction in three fruit fly species, we selected genomic information of three fruit fly species, screened specific genes and single-copy homolog genes, and performed KEGG and GO enrichment analysis on specific genes and single-copy homolog genes of the strong positive select (SP); the results showed that Z. cucurbitae (Coquillett), B. dorsalis (Hendel), and C. capitata (Wiedemann) had seven, 11, and one Vitellogenin-related genes, respectively; Z. cucurbitae (Coquillett) had 84 specific genes enriched in immune system-related pathways; B. dorsalis (Hendel) had 1,121 specific genes enriched in signaling pathways related to cell growth and differentiation; C. capitata (Wiedemann) had 42 specific genes enriched in the degradation and metabolism pathways of exogenous organisms; Z. cucurbitae (Coquillett) may have a stronger immune system; B. dorsalis (Hendel) has a faster developmental and reproductive rate; and C. capitata (Wiedemann) has a higher detoxification capacity. Only one SP single-copy homolog gene (gene name: very long-chain specific acyl-CoA dehydrogenase, mitochondrial) is enriched in the fatty acid metabolic pathway in both Z. cucurbitae (Coquillett) and B. dorsalis (Hendel) as well as in Z. cucurbitae (Coquillett) and C. capitata (Wiedemann). This study provides a molecular basis for studying the reproductive mechanisms of three fruit fly species and provides a scientific basis for developing effective control strategies for fruit flies.