Rachel E. Kalicharan

Biological control strategies are increasingly being explored as sustainable alternatives for managing rice blast disease caused by Magnaporthe oryzae. In this study, we characterized three Bacillus pumilus isolates (DC01, DC09, and DC13) and evaluated their antifungal and plant-beneficial properties against M. oryzae. Whole-genome sequencing revealed multiple biosynthetic gene clusters associated with the production of antimicrobial metabolites. All three isolates inhibited fungal growth in dual-culture assays, whereas heat-stable diffusible antifungal activity was primarily associated with the cell-free supernatants of DC09 and DC13. Exposure to bacterial supernatants disrupted fungal development, inducing abnormal hyphal morphology in M. oryzae characterized by bulbous swelling, altered polarity, and increased branching. Volatile organic compound assays further revealed that the DC isolates suppress fungal growth in the absence of physical contact. The isolates additionally inhibited the growth of other phytopathogenic fungi and selected human bacterial pathogens. All strains exhibited plant growth-promoting traits, including indole-3-acetic acid production and osmotic stress tolerance, whereas DC09 also displayed phosphate-solubilizing activity. Importantly, soil inoculation with the DC isolates significantly reduced rice blast disease severity and induced expression of defense-associated genes involved in jasmonic acid/ethylene signaling and immune priming. Collectively, these findings identify the DC isolates, particularly DC09 and DC13, as promising multi-mechanistic biological control agents for sustainable rice blast management.

Dragon fruit canker (DFC), caused by Neoscytalidium dimidiatum , is a major disease affecting dragon fruit production. However, the pathogen’s nutrient utilization strategies and enzymatic activities remain poorly characterized. Using calcofluor white-based fluorescence microscopy, we show that nutrient limitation restricts fungal growth and development, impairing melanization and arthrosporulation. Carbon utilization assays revealed a preference for maltose, suggesting adaptation to starch-derived sugars. Nitrogen utilization assays indicated efficient assimilation of complex organic nitrogen sources. In addition, we experimentally validated extracellular enzymatic activities involved in host macromolecule degradation, including cellulase, amylase, pectinase and protease activities. Together, these findings provide insight into the physiological traits of N. dimidiatum associated with growth and development under varying nutrient conditions.

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. Upon galactose induction, expression of MoPARP1 reduced yeast growth, whereas a catalytically inactive mutant showed no defect, indicating that the growth phenotype depends on PARP catalytic activity. Consistent with this requirement, PARylation was detected in MoPARP1-expressing yeast cells but not in the catalytic mutant. 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.

Plant pathogens pose significant threats to global cereal crop production, particularly for essential crops such as rice and wheat, which are fundamental to global food security and provide nearly 40% of the global caloric intake. As the global population continues to rise, increasing agricultural production to meet food demands becomes even more critical. However, the production of these vital crops is constantly threatened by phytopathological diseases, especially those caused by fungal pathogens such as Magnaporthe oryzae, the causative agent of rice blast disease; Fusarium graminearum, responsible for Fusarium head blight in wheat; and Zymoseptoria tritici, the source of Septoria tritici blotch. All three pathogens are hemibiotrophic, initially colonizing the host through a biotrophic, symptomless lifestyle, followed by causing cell death through the necrotrophic phase. Additionally, they deploy a diverse range of effectors, including proteinaceous and non-proteinaceous molecules, to manipulate fundamental host cellular processes, evade immune responses, and promote disease progression. This review discusses recent advances in understanding the effector biology of these three pathogens, highlighting both the shared functionalities and unique molecular mechanisms they employ to regulate conserved elements of host pathways, such as directly manipulating gene transcription in host nuclei, disrupting reactive oxygen species signaling, interfering with protein stability, and undermining host structural integrity. By detailing these complex interactions, the review explores potential targets for innovative control measures and emphasizes the need for further research to develop effective strategies against these destructive pathogens in the face of evolving environmental and agricultural challenges. [ ] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

The purpose of this document is to increase awareness of rice blast disease by describing its lifestyle, symptoms, and current disease mitigation practices. Given that the Everglades Agricultural Area (EAA) plays a vital role in rice cultivation, this publication is also intended for Florida rice growers to be used as a diagnostic field guide in the identification and management of rice blast disease. Written by Nalleli Garcia, Rachel Kalicharan, and Jessie Fernandez Garcia, and published by the UF/IFAS Department of Microbiology and Cell Science, September 2024.

Identified over twenty years ago and distantly related to animal caspases are a group of cysteine proteases known as metacaspases. Throughout the years, much like caspase roles in metazoans, metacaspases have been shown to be involved in regulating cellular death in non-metazoan organisms. Yet, continued research on metacaspases describes these proteins as intricate and multifunctional, displaying striking diversity on distinct biological functions. In this review, we intend to describe the recent advances in our understanding of the divergence of metacaspase functionality in plants and fungi. We will dissect the duality of metacaspase activity in the context of plant-pathogen interactions, providing a unique lens from which to characterize metacaspases in the development, immunity, and stress responses of plants, and the development and virulence of fungi. Furthermore, we explore the evolutionary trajectory of fungal metacaspases to delineate their structure and function. Bridging the gap between metacaspase roles in immunity and pathogenicity of plant-pathogen interactions can enable more effective and targeted phytopathogen control efforts to increase production of globally important food crops. Therefore, the exploitation and manipulation of metacaspases in plants or fungi represent new potential avenues for developing mitigation strategies against plant pathogens.