The Necrotroph Botrytis cinerea BcSpd1 Plays a Key Role in Modulating Both Fungal Pathogenic Factors and Plant Disease Development

A LysM Effector Mediates Adhesion and Plant Immunity Suppression in the Necrotrophic Fungus Botrytis cinerea

LysM effectors are suppressors of chitin-triggered plant immunity in biotrophic and hemibiotrophic fungi. In necrotrophic fungi, LysM effectors might induce a mechanism to suppress host immunity during the short asymptomatic phase they establish before these fungi activate plant defenses and induce host cell death leading to necrosis. Here, we characterize a secreted LysM protein from a major necrotrophic fungus, Botrytis cinerea, called BcLysM1. Transcriptional induction of BcLysM1 gene was observed in multicellular appressoria, called infection cushions, in unicellular appressoria and in the early phase of infection on bean leaves. We confirmed that BcLysM1 protein binds chitin in the fungus cell wall and protects hyphae against degradation by external chitinases. This effector is also able to suppress the chitin-induced ROS burst in Arabidopsis thaliana, suggesting sequestration of chitooligosaccharides in apoplast during infection. Moreover, contribution of BcLysM1 in infection initiation and in adhesion to bean leaf surfaces were demonstrated. Our data show for the first time that a LysM effector can play a dual role in mycelial adhesion and suppression of chitin-triggered host immunity, both of which occur during the early asymptomatic phase of infection by necrotrophic fungi.

Role of Methyl thiobutyrate to Botrytis cinerea on cucumber

Introduction

Botrytis cinerea is a major agricultural pathogen that causes significant economic Q7 losses worldwide, affecting various crops, including cucumbers. Developing environmentally sustainable control strategies for this pathogen is crucial. Methyl thiobutyrate (MTB), a small organic molecule identified in the volatile organic compounds (VOCs) of biocontrol bacteria, has demonstrated potential in inhibiting B. cinerea both in vitro and in vivo.

Methods

In this study, the efficacy of MTB against cucumber gray mold disease was examined by assessing the in vitro and in vivo activities of MTB against B. cinerea and analyzing the transcriptomic data from MTB-treated cucumber leaves infected with B. cinerea.

Results and discussion

This study shows that a 2 mg/mL solution of MTB inhibits B. cinerea growth by 98.6% in vitro. In vivo, MTB effectively reduces B. cinerea infection in cucumbers, alleviates necrotic damage in leaf tissues, and significantly reduces disease severity. Transcriptomic analysis reveals that MTB activates the plant immune responses by modulating key MAPK cascade signaling genes and upregulating basal defense genes, including chitinase, pectinase, and lignin biosynthesis genes. Furthermore, MTB influences the signaling pathways of salicylic acid (SA), jasmonic acid (JA), and ethylene (ET), resulting in the upregulation of genes such as peroxidase (POD), phenylalanine ammonia-lyase (PAL), lipoxygenase (LOX), and ethyleneresponsive transcription factors (ERFs). These results demonstrate the potential of MTB as an effective biocontrol agent against B. cinerea and provide valuable insights into its underlying mechanisms of action.

The Good, the Bad, and the Fungus: Insights into the Relationship Between Plants, Fungi, and Oomycetes in Hydroponics

Hydroponic systems are examples of controlled environment agriculture (CEA) and present a promising alternative to traditional farming methods by increasing productivity, profitability, and sustainability. In hydroponic systems, crops are grown in the absence of soil and thus lack the native soil microbial community. This review focuses on fungi and oomycetes, both beneficial and pathogenic, that can colonize crops and persist in hydroponic systems. The symptomatology and mechanisms of pathogenesis for Botrytis, Colletotrichum, Fulvia, Fusarium, Phytophthora, Pythium, and Sclerotinia are explored for phytopathogenic fungi that target floral organs, leaves, roots, and vasculature of economically important hydroponic crops. Additionally, this review thoroughly explores the use of plant growth-promoting fungi (PGPF) to combat phytopathogens and increase hydroponic crop productivity; details of PGP strategies and mechanisms are discussed. The benefits of Aspergillus, Penicillium, Taloromyces, and Trichoderma to hydroponics systems are explored in detail. The culmination of these areas of research serves to improve the current understanding of the role of beneficial and pathogenic fungi, specifically in the hydroponic microbiome.

Pseudocercospora fijiensis Conidial Germination Is Dominated by Pathogenicity Factors and Effectors

Conidia play a vital role in the survival and rapid spread of fungi. Many biological processes of conidia, such as adhesion, signal transduction, the regulation of oxidative stress, and autophagy, have been well studied. In contrast, the contribution of pathogenicity factors during the development of conidia in fungal phytopathogens has been poorly investigated. To date, few reports have centered on the pathogenicity functions of fungal phytopathogen conidia. Pseudocercospora fijiensis is a hemibiotrophic fungus and the causal agent of the black Sigatoka disease in bananas and plantains. Here, a conidial transcriptome of P. fijiensis was characterized computationally. Carbohydrates, amino acids, and lipid metabolisms presented the highest number of annotations in Gene Ontology. Common conidial functions were found, but interestingly, pathogenicity factors and effectors were also identified. Upon analysis of the resulting proteins against the Pathogen-Host Interaction (PHI) database, 754 hits were identified. WideEffHunter and EffHunter effector predictors identified 618 effectors, 265 of them were shared with the PHI database. A total of 1107 conidial functions devoted to pathogenesis were found after our analysis. Regarding the conidial effectorome, it was found to comprise 40 canonical and 578 non-canonical effectors. Effectorome characterization revealed that RXLR, LysM, and Y/F/WxC are the largest effector families in the P. fijiensis conidial effectorome. Gene Ontology classification suggests that they are involved in many biological processes and metabolisms, expanding our current knowledge of fungal effectors.

Inhibition of chitin deacetylases to attenuate plant fungal diseases

Phytopathogenic fungi secrete chitin deacetylase (CDA) to escape the host's immunological defense during infection. Here, we showed that the deacetylation activity of CDA toward chitin is essential for fungal virulence. Five crystal structures of two representative and phylogenetically distant phytopathogenic fungal CDAs, VdPDA1 from Verticillium dahliae and Pst_13661 from Puccinia striiformis f. sp. tritici, were obtained in ligand-free and inhibitor-bound forms. These structures suggested that both CDAs have an identical substrate-binding pocket and an Asp-His-His triad for coordinating a transition metal ion. Based on the structural identities, four compounds with a benzohydroxamic acid (BHA) moiety were obtained as phytopathogenic fungal CDA inhibitors. BHA exhibited high effectiveness in attenuating fungal diseases in wheat, soybean, and cotton. Our findings revealed that phytopathogenic fungal CDAs share common structural features, and provided BHA as a lead compound for the design of CDA inhibitors aimed at attenuating crop fungal diseases.

One population, multiple lifestyles: Commensalism and pathogenesis in the human mycobiome

Candida auris and Candida albicans can result in invasive fungal diseases. And yet, these species can stably and asymptomatically colonize human skin and gastrointestinal tracts. To consider these disparate microbial lifestyles, we first review factors shown to influence the underlying microbiome. Structured by the damage response framework, we then consider the molecular mechanisms deployed by C. albicans to switch between commensal and pathogenic lifestyles. Next, we explore this framework with C. auris to highlight how host physiology, immunity, and/or antibiotic receipt are associated with progression from colonization to infection. While treatment with antibiotics increases the risk that an individual will succumb to invasive candidiasis, the underlying mechanisms remain unclear. Here, we describe several hypotheses that may explain this phenomenon. We conclude by highlighting future directions integrating genomics with immunology to advance our understanding of invasive candidiasis and human fungal disease.