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

Abstract

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.

Uncovering the multifaceted properties of 6-pentyl-alpha-pyrone for control of plant pathogens

“…(B) 6-PP regulates production of mycotoxin in plant pathogens by downregulation of vel complex and fub10 genes, key players to regulate expression of the cluster Fub and synthesis of aflatoxin. ( Niehaus et al., 2014 ; Ismaiel and Ali, 2017 ; Hao et al., 2023 ) (C) 6-PP regulates the TOR signaling pathway, impacting different development process such as growth, sporangium formation, encystment, zoospore release and pathogenicity ( Wu et al., 2023 ). (D) Alteration of organic acids metabolism via the Krebs cycle may affect the physiology of plant pathogens.…”

“…Recent studies have also suggested the involvement of specific signaling transduction pathways in the interaction of 6-PP with fungi and oomycetes ( Xing et al., 2023 ). For instance, in P. litchii , 6-PP triggers the upregulation of genes associated with the Ser/Thr protein kinase target of the rapamycin (TOR) pathway, such as PlCytochrome C and the YinYang1 transcription factor, while concurrently downregulating potential negative regulators of this pathway like PlSpm1 and PlrhoH12 ( Wu et al., 2023 ). These findings imply that 6-PP might inhibit the vegetative growth, sporulation, cyst formation, and pathogenesis of P. litchii by modulating the activation of the TOR pathway ( Figure 3C ).…”

“…In fungi, the proteins equivalent to Na+, K+ATPases are the proton-ATPases involved in regulation of hypersensitivity to osmotic stresses, cell wall stressors and oxidative stress ( Mou et al., 2020 ; Deng et al., 2023 ). In fungi, 6-PP may also target other enzymes involved in critical metabolic pathways, such as glycolysis, the tricarboxylic acid (TCA) cycle, and fatty acid biosynthesis as well as key components associated with nutrients sensing such as TOR kinase signaling ( Jin et al., 2020 ; Lim et al., 2023 ; Liu et al., 2023 ; Wu et al., 2023 ). By inhibiting enzymes within these pathways, 6-PP disrupts the production of essential metabolites and intermediates, impairing the pathogen’s ability to generate energy and synthesize macromolecules necessary for growth and replication ( Jin et al., 2020 ).…”