Life Sciences Commons^™

Principles Of Carbon Catabolite Repression In The Rice Blast Fungus: Tps1, Nmr1-3, And A Mate–Family Pump Regulate Glucose Metabolism During Infection, Jessie Fernandez, Janet D. Wright, David E. Hartline, Cristian Fernando Quispe, Nandakumar Madayiputhiya, Richard A. Wilson

Fungal Molecular Plant-Microbe Interactions

Understanding the genetic pathways that regulate how pathogenic fungi respond to their environment is paramount to developing effective mitigation strategies against disease. Carbon catabolite repression (CCR) is a global regulatory mechanism found in a wide range of microbial organisms that ensures the preferential utilization of glucose over less favourable carbon sources, but little is known about the components of CCR in filamentous fungi. Here we report three new mediators of CCR in the devastating rice blast fungus Magnaporthe oryzae: the sugar sensor Tps1, the Nmr1-3 inhibitor proteins, and the multidrug and toxin extrusion (MATE)-family pump, Mdt1. Using simple plate …

Fungal Virulence And Development Is Regulated By Alternative Pre-Mrna 3′End Processing In Magnaporthe Oryzae, Marina Franceschetti, Emilio Bueno, Richard A. Wilson, Sara L. Tucker, Concepción Gómez-Mena, Grant Calder, Ane Sesma

Fungal Molecular Plant-Microbe Interactions

RNA-binding proteins play a central role in post-transcriptional mechanisms that control gene expression. Identification of novel RNA-binding proteins in fungi is essential to unravel post-transcriptional networks and cellular processes that confer identity to the fungal kingdom. Here, we carried out the functional characterisation of the filamentous fungus-specific RNAbinding protein RBP35 required for full virulence and development in the rice blast fungus. RBP35 contains an N-terminal RNA recognition motif (RRM) and six Arg-Gly-Gly tripeptide repeats. Immunoblots identified two RBP35 protein isoforms that show a steady-state nuclear localisation and bind RNA in vitro. RBP35 coimmunoprecipitates in vivo with Cleavage Factor I (CFI) …

The Sugar Sensor, Trehalose-6-Phosphate Synthase (Tps1), Regulates Primary And Secondary Metabolism During Infection By The Rice Blast Fungus: Will Magnaporthe Oryzae’S “Sweet Tooth” Become Its “Achilles’ Heel”?, Jessie Fernandez, Richard A. Wilson

Fungal Molecular Plant-Microbe Interactions

Rice blast disease is considered one of the most serious diseases of cultivated rice and is mediated by the causal agent, Magnaporthe oryzae. During infection, dome-shaped fungal cells, called appressoria, form on the surface of the leaf and generate turgor through the accumulation of glycerol. This enormous pressure is directed down onto a thin penetration hypha emerging from the base of the cell, forcing it through the surface of the rice leaf and allowing fungal colonization of the plant interior. The non-reducing disaccharide, trehalose, is present in conidia of M. oryzae and is mobilized during appressorium formation. The first step …

An Nadph-Dependent Genetic Switch Regulates Plant Infection By The Rice Blast Fungus, Richard A. Wilson, Robert P. Gibson, Cristian Quispe, Jennifer A. Littlechild, Nicholas J. Talbot

Fungal Molecular Plant-Microbe Interactions

To cause rice blast disease, the fungus Magnaporthe oryzae breaches the tough outer cuticle of the rice leaf by using specialized infection structures called appressoria. These cells allow the fungus to invade the host plant and proliferate rapidly within leaf tissue. Here, we show that a unique NADPH-dependent genetic switch regulates plant infection in response to the changing nutritional and redox conditions encountered by the pathogen. The biosynthetic enzyme trehalose-6-phosphate synthase (Tps1) integrates control of glucose-6-phosphate metabolism and nitrogen source utilization by regulating the oxidative pentose phosphate pathway, the generation of NADPH, and the activity of nitrate reductase. We report …

Oxygenase Coordination Is Required For Morphological Transition And The Host-Fungus Interaction Of Aspergillus Flavus, Sigal Horowitz Brown, James B. Scott, Jeyanthi Bhaheetharan, William C. Sharpee, Lane Milde, Richard A. Wilson

Fungal Molecular Plant-Microbe Interactions

Oxylipins, a class of oxygenase-derived unsaturated fatty acids, are important signal molecules in many biological systems. Recent characterization of an Aspergillus flavus lipoxygenase gene, lox, revealed its importance in maintaining a density-dependent morphology switch from sclerotia to conidia as population density increased. Here, we present evidence for the involvement of four more oxylipingenerating dioxygenases (PpoA, PpoB, PpoC, and PpoD) in A. flavus density-dependent phenomena and the effects of loss of these genes on aflatoxin production and seed colonization. Although several single mutants showed alterations in the sclerotia-to-conidia switch, the major effect was observed in a strain downregulated for all …

Under Pressure: Investigating The Biology Of Plant Infection By Magnaporthe Oryza, Nicholas J. Talbot, Richard A. Wilson

Fungal Molecular Plant-Microbe Interactions

The filamentous fungus Magnaporthe oryzae causes rice blast, the most serious disease of cultivated rice. Cellular differentiation of M. oryzae forms an infection structure called the appressorium, which generates enormous cellular turgor that is sufficient to rupture the plant cuticle. Here, we show how functional genomics approaches are providing new insight into the genetic control of plant infection by M. oryzae. We also look ahead to the key questions that need to be addressed to provide a better understanding of the molecular processes that lead to plant disease and the prospects for sustainable control of rice blast.

Fungal Physiology: A Future Perspective, Richard A. Wilson, Nicholas J. Talbot

Fungal Molecular Plant-Microbe Interactions

The study of fungal physiology is set to change dramatically in the next few years as highly scalable technologies are deployed allowing accurate measurement and identification of metabolites, proteins and transcripts within cells. The advent of next-generation DNA-sequencing technologies will also provide genome sequence information from large numbers of industrially relevant and pathogenic fungal species, and allow comparative genome analysis between strains and populations of fungi. When coupled with advances in gene functional analysis, protein-protein interaction studies, live cell imaging and mathematical modelling, this promises a step-change in our understanding of how fungal cells operate as integrated dynamic living systems

Fundamental Contribution Of Β-Oxidation To Polyketide Mycotoxin Production In Planta, Lori A. Maggio-Hall, Richard A. Wilson, Nancy P. Keller

Fungal Molecular Plant-Microbe Interactions

Seed contamination with polyketide mycotoxins, including aflatoxin (AF) and sterigmatocystin (ST) produced by Aspergillus spp., is an agricultural, economic, and medical issue worldwide. Acetyl-CoA, the fundamental building block of all known fungal polyketides, is generated by a large number of biochemical pathways, including β-oxidation of fatty acids and glycolysis of sugars. We present several lines of evidence to support a major role for seed fatty acids in formation of AF and ST in A. flavus, A. parasiticus, and A. nidulans. Aspergillus strains exhibiting canonical signs of oleic acid–induced peroxisome proliferation, including increased catalase activity, β-oxidation gene expression, and …

Deletion Of The Δ12-Oleic Acid Desaturase Gene Of A Nonaflatoxigenic Aspergillus Parasiticus Field Isolate Affects Conidiation And Sclerotial Development, Perng Kuang Chang, Richard A. Wilson, Nancy P. Keller, Thomas E. Cleveland

Fungal Molecular Plant-Microbe Interactions

Aims: To investigate how linoleic acid affects conidial production and sclerotial development in a strictly mitotic Aspergillus parasiticus field isolate as related to improving biocompetitivity of atoxigenic Aspergillus species.

Methods and Results: We disrupted A. parasiticus Δ12-oleic acid desaturase gene (odeA) responsible for the conversion of oleic acid to linoleic acid. We examined conidiation and sclerotial development of SRRC 2043 and three isogenic mutant strains deleted for the odeA gene (DodeA), either with or without supplementing linoleic acid, on one complex potato dextrose agar (PDA) medium and on two defined media: nitrate-containing Czapek agar (CZ) and Cove’s ammonium …

Two Δ9-Stearic Acid Desaturases Are Required For Aspergillus Nidulans Growth And Development, Richard A. Wilson, Perng-Kuang Chang, Agnieszka Dobrzyn, James B. Ntambi, Robert Zarnowski, Nancy P. Keller

Fungal Molecular Plant-Microbe Interactions

Unsaturated fatty acids are important constituents of all cell membranes and are required for normal growth. In the filamentous fungus Aspergillus nidulans, unsaturated fatty acids and their derivatives also influence asexual (conidial) and sexual (ascospore) sporulation processes. To investigate the relationship between fatty acid metabolism and fungal development, we disrupted the A. nidulans sdeA and sdeB genes, both encoding Δ9-stearic acid desaturases responsible for the conversion of palmitic acid (16:0) and stearic acid (18:0) to palmitoleic acid (16:1) and oleic acid (18:1). The effects of sdeA deletion on development were profound, such that growth, conidial and ascospore production were …

Characterization Of The Aspergillus Parasiticus Δ12-Desaturase Gene: A Role For Lipid Metabolism In The Aspergillus-Seed Interaction, Richard A. Wilson, Ana M. Calvo, Perng-Kuang Chang, Nancy P. Keller

Fungal Molecular Plant-Microbe Interactions

In the mycotoxigenic oilseed pathogens Aspergillus flavus and Aspergillus parasiticus and the model filamentous fungus Aspergillus nidulans, unsaturated fatty acids and their derivatives act as important developmental signals that affect asexual conidiospore, sexual ascospore and/or sclerotial development. To dissect the relationship between lipid metabolism and fungal development, an A. parasiticus Δ¹²-desaturase mutant that was unable to convert oleic acid to linoleic acid and was thus impaired in polyunsaturated fatty acid biosynthesis was generated. The Δ¹²-desaturase mutant demonstrates delayed spore germination, a twofold reduction in growth, a reduced level of conidiation and complete loss of sclerotial …

Relationship Between Secondary Metabolism And Fungal Development, Ana M. Calvo, Richard A. Wilson, Jin Woo Bok, Nancy P. Keller

Fungal Molecular Plant-Microbe Interactions

Details findings related to the relationship between secondary metabolism and fungal development.

Cultivar-Dependent Expression Of A Maize Lipoxygenase Responsive To Seed Infesting Fungi, Richard A. Wilson, Harold W. Gardner, Nancy P. Keller

Fungal Molecular Plant-Microbe Interactions

Maize kernels are highly susceptible to Aspergillus spp. infection and aflatoxin (AF) contamination. Fatty acid signaling molecules appear to mediate the plant–fungal interaction by affecting the growth, development, and AF production of the fungus. In particular, fatty acid derivatives of the plant lipoxygenase (LOX) pathway are implicated in the Aspergillus spp.-seed interaction. The 9(S)-hydroperoxide derivative of linoleic acid promotes transcription of AF genes, whereas the 13(S)-hydroperoxide derivative decreases AF gene expression and production; both are sporulation factors. Our goal was to identify LOX genes responsive to Aspergillus spp. colonization and determine their specificities, 9(S)- …

Mutational Analysis Of Area, A Transcriptional Activator Mediating Nitrogen Metabolite Repression In Aspergillus Nidulans And A Member Of The “Streetwise” Gata Family Of Transcription Factors, Richard A. Wilson, Herbert N. Arst Jr.

Fungal Molecular Plant-Microbe Interactions

Details a mutational analysis of AREA, a transcriptional activator mediating nitrogen metabolite repression in Aspergillus nidulans and a member of the “streetwise” GATA family of transcription factors.