Metabonomics analysis of postharvest citrus response to Penicillium digitatum infection

A secreted fungal laccase targets the receptor kinase OsSRF3 to inhibit OsBAK1-OsSRF3-mediated immunity in rice

The identification effector targets and characterization of their functions are crucial for understanding pathogen infection mechanisms and components of plant immunity. Here, we identify the effector UgsL, a ustilaginoidin synthetase with a key role in regulating virulence of the rice false smut fungus Ustilaginoidea virens. Heterologous expression of UgsL in rice (Oryza sativa) enhances plant susceptibility to multiple pathogens, and host-induced gene silencing of UgsL enhances plant resistance to U. virens, indicating that UgsL inhibits rice immunity. UgsL interacts with STRUBBELIG RECEPTOR KINASE 3 (OsSRF3). Genome editing and overexpression of OsSRF3 demonstrate that OsSRF3 plays a pivotal role in the resistance of rice to multiple pathogens. Remarkably, overexpressing OsSRF3 enhances resistance without adversely affecting plant growth or yield. We show that BRASSINOSTEROID RECEPTOR-ASSOCIATED KINASE 1 (OsBAK1) interacts with and phosphorylates OsSRF3 to activate pathogen-triggered immunity, inducing the mitogen-activated protein kinase cascade, a reactive oxygen species burst, callose deposition, and expression of defense-related genes. UgsL interferes with the phosphorylation of OsSRF3 by OsBAK1. Furthermore, UgsL mediates OsSRF3 degradation by facilitating its association with the ubiquitin-26S proteasome. Our results reveal that OsSRF3 positively regulates immunity in rice and that UgsL mediates its degradation, thereby inhibiting the activation of OsBAK1-OsSRF3-mediated immune pathways.

Metabolomics approach to understand molecular mechanisms involved in fungal pathogen-citrus pathosystems

Citrus is a crucial crop with a significant economic impact globally. However, postharvest decay caused by fungal pathogens poses a considerable threat, leading to substantial financial losses. Penicillium digitatum, Penicillium italicum, Geotrichum citri-aurantii and Phyllosticta citricarpa are the main fungal pathogens, causing green mold, blue mold, sour rot and citrus black spot diseases, respectively. The use of chemical fungicides as a control strategy in citrus raises concerns about food and environmental safety. Therefore, understanding the molecular basis of host-pathogen interactions is essential to find safer alternatives. This review highlights the potential of the metabolomics approach in the search for bioactive compounds involved in the pathogen-citrus interaction, and how the integration of metabolomics and genomics contributes to the understanding of secondary metabolites associated with fungal virulence and the fungal infection mechanisms. Our goal is to provide a pipeline combining metabolomics and genomics that can effectively guide researchers to perform studies aiming to contribute to the understanding of the fundamental chemical and biochemical aspects of pathogen-host interactions, in order to effectively develop new alternatives for fungal diseases in citrus cultivation. We intend to inspire the scientific community to question unexplored biological systems, and to employ diverse analytical approaches and metabolomics techniques to address outstanding questions about the non-studied pathosystems from a chemical biology perspective.

Isolation and Identification of Pathogens Causing Blue Mold of Lanzhou Lily during Postharvest Storage and Control of Disease and Mycotoxin Accumulation by Ozone Treatment

Blue mold (penicilliosis) is a common disease of Lanzhou lily (Lilium davidii var. willmottiae) during postharvest storage, which not only seriously affects the appearance and reduces the quality of lily bulbs, but also leads to the accumulation of mycotoxins in rotten lily tissues, seriously endangering human health. Therefore, it is of great significance to clarify the main isolates causing postharvest blue mold of fresh Lanzhou lily and put forward effective measures to control the disease caused by these pathogens. In this study, pathogens were isolated and purified from the naturally diseased blue-mold tissue of Lanzhou lily, and then morphological and molecular biology techniques were applied to identify the isolates, verify the pathogenicity, determine the disease index and disease incidence, and finally, to analyze the control effect of ozone treatment on the blue mold of lily scale and mycotoxin accumulation. The results indicated that the main isolates causing postharvest blue mold of lily were Talaromyces adpressus, Penicillium gladioli, T. calidominioluteus, and P. polonicum. The pathogenicity test showed that P. gladioli and P. polonicum had a higher disease index than T. calidominioluteus and T. adpressus. Ozone treatment significantly reduced the incidence of disease caused by P. gladioli and P. polonicum, and effectively controlled the accumulation of patulin. This study characterized the main pathogens causing blue mold of postharvest Lanzhou lily during storage, and confirmed ozone application has a significant inhibitory effect on blue mold development and patulin accumulation in Lanzhou lily, which could be helpful in commercially controlling blue mold of postharvest Lanzhou lily during storage.