Kalicharan, R. | bioRxiv Science

bioRxiv2025

Yeast as a platform to dissect poly(ADP-ribose) polymerase function from Magnaporthe oryzae and evaluate PARP inhibitors

Poly(ADP-ribose) polymerases (PARPs) regulate genome maintenance through NAD+-dependent ADP-ribosylation, yet PARP function in fungi remains poorly defined. Here, we reconstituted the activity of the Magnaporthe oryzae PARP1 homolog (MoPARP1) in Saccharomyces cerevisiae, a genetically tractable organism that lacks endogenous PARP enzymes. Galactose-induced expression of MoPARP1 reduced yeast growth, whereas a catalytically inactive mutant showed no defect, indicating that the growth phenotype depends on PARP catalytic activity. In a multidrug transporter-deficient background, the PARP inhibitor 3-aminobenzamide and the clinically used PARP inhibitor olaparib rescued the growth of MoPARP1-expressing strains, establishing a framework for inhibitor testing in vivo. Finally, MoPARP1-GFP localized to the nucleus independent of catalytic activity, supporting correct targeting in this heterologous system. Together, these findings establish yeast as a platform to dissect fungal PARP biology and evaluate chemical inhibition.

molecular biology↗

bioRxiv2025

Nutrient utilization and degradative enzyme activity of the dragon fruit canker pathogen, Neoscytalidium dimidiatum

Dragon fruit canker (DFC), caused by the pathogenic fungus Neoscytalidium dimidiatum, is a severe disease that threatens dragon fruit production worldwide. Current management efforts largely rely on fungicide applications and sanitation measures; however, the pathogens molecular genetic characterization, nutrient utilization preferences, and extracellular enzyme activities remain poorly understood. Using calcofluor white-based fluorescence microscopy, we demonstrate that nutrient limitation significantly restricts the growth and maturation of N. dimidiatum, impairing melanization and sporulation. Carbon utilization assays revealed a preference for maltose, suggesting reliance on starch-derived sugars. In addition, nitrogen utilization assays indicated efficient assimilation of complex organic nitrogen sources rich in peptides and amino acids. Finally, we experimentally validated extracellular enzymatic activities involved in host macromolecule degradation, including cellulase, amylase, pectinase, and protease activities. Collectively, these findings provide new insights into the physiology and pathogenic potential of N. dimidiatum and establish a foundation for developing improved strategies to mitigate DFC. Impact StatementNeoscytalidium dimidiatum is the causal agent of dragon fruit canker (DFC), one of the most devastating diseases affecting dragon fruit. Here, we investigated key features of N. dimidiatum biology relevant to disease development, including nutrient preferences and degradative enzyme activity. Our findings indicate that N. dimidiatum preferentially utilizes maltose as a carbon source, consistent with the use of starch-derived sugars, and grows efficiently on rich, complex organic nitrogen sources. Plate-based enzymatic assays aligned with these nutrient utilization patterns, revealing cellulase, amylase, pectinase, and protease activities. Collectively, this study provides new insights into N. dimidiatum physiology and establishes a foundation for future virulence studies that can ultimately support the development of improved DFC mitigation strategies.

microbiology↗