Downregulation of the ypdA Gene Encoding an Intermediate of His-Asp Phosphorelay Signaling in Aspergillus nidulans Induces the Same Cellular Effects as the Phenylpyrrole Fungicide Fludioxonil

Many eukaryotic histidine-to-aspartate (His-Asp) phosphorelay systems consist of three types of signal transducers: a His-kinase (HK), a response regulator (RR), and a histidine-containing phosphotransfer intermediate (HPt). In general, the HPt acts as an intermediate between the HK and the RR and is indispensable for inducing appropriate responses to environmental stresses. In a previous study, we attempted but were unable to obtain deletion mutants of the ypdA gene in order to characterize its function in the filamentous fungus Aspergillus nidulans. In the present study, we constructed the CypdA strain in which ypdA expression is conditionally regulated by the A. nidulans alcA promoter. We constructed CypdA strains with RR gene disruptions (CypdA-sskAΔ, CypdA-srrAΔ, and CypdA-sskAΔsrrAΔ). Suppression of YpdA induced by ypdA downregulation activated the downstream HogA mitogen-activated protein kinase cascade. YpdA suppression caused severe growth defects and abnormal hyphae, with features such as enhanced septation, a decrease in number of nuclei, nuclear fragmentation, and hypertrophy of vacuoles, both regulated in an SskA–dependent manner. Fludioxonil treatment caused the same cellular responses as ypdA suppression. The growth-inhibitory effects of fludioxonil and the lethality caused by ypdA downregulation may be caused by the same or similar mechanisms and to be dependent on both the SskA and SrrA pathways.

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Whole-Genome Analysis of Two-Component Signal Transduction Genes in Fungal Pathogens

Eukaryotic Cell ◽

10.1128/ec.2.6.1151-1161.2003 ◽

2003 ◽

Vol 2 (6) ◽

pp. 1151-1161 ◽

Cited By ~ 200

Author(s):

Natalie L. Catlett ◽

Olen C. Yoder ◽

B. Gillian Turgeon

Keyword(s):

Fungal Pathogens ◽

Response Regulator ◽

Fusarium Verticillioides ◽

Mitogen Activated Protein Kinase ◽

Whole Genome Analysis ◽

Filamentous Ascomycete ◽

Two Component ◽

Mitogen Activated Protein ◽

Kinase Cascade ◽

Botryotinia Fuckeliana

ABSTRACT Two-component phosphorelay systems are minimally comprised of a histidine kinase (HK) component, which autophosphorylates in response to an environmental stimulus, and a response regulator (RR) component, which transmits the signal, resulting in an output such as activation of transcription, or of a mitogen-activated protein kinase cascade. The genomes of the yeasts Saccharomyces cerevisiae, Schizosaccharomyces pombe, and Candida albicans encode one, three, and three HKs, respectively. In contrast, the genome sequences of the filamentous ascomycetes Neurospora crassa, Cochliobolus heterostrophus (Bipolaris maydis), Gibberella moniliformis (Fusarium verticillioides), and Botryotinia fuckeliana (Botrytis cinerea) encode an extensive family of two-component signaling proteins. The putative HKs fall into 11 classes. Most of these classes are represented in each filamentous ascomycete species examined. A few of these classes are significantly more prevalent in the fungal pathogens than in the saprobe N. crassa, suggesting that these groups contain paralogs required for virulence. Despite the larger numbers of HKs in filamentous ascomycetes than in yeasts, all of the ascomycetes contain virtually the same downstream histidine phosphotransfer proteins and RR proteins, suggesting extensive cross talk or redundancy among HKs.

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ras2 Controls Morphogenesis, Pheromone Response, and Pathogenicity in the Fungal Pathogen Ustilago maydis

Eukaryotic Cell ◽

10.1128/ec.1.6.954-966.2002 ◽

2002 ◽

Vol 1 (6) ◽

pp. 954-966 ◽

Cited By ~ 78

Author(s):

Nancy Lee ◽

James W. Kronstad

Keyword(s):

Protein Kinase ◽

Map Kinase ◽

Ustilago Maydis ◽

Mitogen Activated Protein Kinase ◽

Gene Encoding ◽

Mitogen Activated Protein ◽

Kinase Cascade ◽

Map Kinase Pathway ◽

Altered Cell ◽

Kinase Pathway

ABSTRACT Ustilago maydis, a pathogen of maize, is a useful model for the analysis of mating, pathogenicity, and the morphological transition between budding and filamentous growth in fungi. As in other fungi, these processes are regulated by conserved signaling mechanisms, including the cyclic AMP (cAMP)/protein kinase A (PKA) pathway and at least one mitogen-activated protein kinase (MAP kinase) pathway. A current challenge is to identify additional factors that lie downstream of the cAMP pathway and that influence morphogenesis in U. maydis. In this study, we identified suppressor mutations that restored budding growth to a constitutively filamentous mutant with a defect in the gene encoding a catalytic subunit of PKA. Complementation of one suppressor mutation unexpectedly identified the ras2 gene, which is predicted to encode a member of the well-conserved ras family of small GTP-binding proteins. Deletion of the ras2 gene in haploid cells altered cell morphology, eliminated pathogenicity on maize seedlings, and revealed a role in the production of aerial hyphae during mating. We also used an activated ras2 allele to demonstrate that Ras2 promotes pseudohyphal growth via a MAP kinase cascade involving the MAP kinase kinase Fuz7 and the MAP kinase Ubc3. Overall, our results reveal an additional level of crosstalk between the cAMP signaling pathway and a MAP kinase pathway influenced by Ras2.

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Molecular cloning and characterization of human JNKK2, a novel Jun NH2-terminal kinase-specific kinase.

Molecular and Cellular Biology ◽

10.1128/mcb.17.12.7407 ◽

1997 ◽

Vol 17 (12) ◽

pp. 7407-7416 ◽

Cited By ~ 79

Author(s):

Z Wu ◽

J Wu ◽

E Jacinto ◽

M Karin

Keyword(s):

Expressed Sequence Tag ◽

Uv Light ◽

Osmotic Shock ◽

Mitogen Activated Protein Kinase ◽

Dependent Manner ◽

Gene Encoding ◽

Mapk Cascades ◽

Mitogen Activated Protein ◽

A Cell ◽

Jnk Cascade

At least three mitogen-activated protein kinase (MAPK) cascades were identified in mammals, each consisting of a well-defined three-kinase module composed of a MAPK, a MAPK kinase (MAPKK), and a MAPKK kinase (MAPKKK). These cascades play key roles in relaying various physiological, environmental, or pathological signals from the environment to the transcriptional machinery in the nucleus. One of these MAPKs, c-Jun N-terminal kinase (JNK), stimulates the transcriptional activity of c-Jun in response to growth factors, proinflammatory cytokines, and certain environmental stresses, such as short wavelength UV light or osmotic shock. The JNKs are directly activated by the MAPKK JNKK1/SEK1/MKK4. However, inactivation of the gene encoding this MAPKK by homologous recombination suggested the existence of at least one more JNK-activating kinase. Recently, the JNK cascade was found to be structurally and functionally conserved in Drosophila, where DJNK is activated by the MAPKK DJNKK (hep). By a database search, we identified an expressed sequence tag (EST) encoding a portion of human MAPKK that is highly related to DJNKK (hep). We used this EST to isolate a full-length cDNA clone encoding a human JNKK2. We show that JNKK2 is a highly specific JNK kinase. Unlike JNKK1, it does not activate the related MAPK, p38. Although the regulation of JNKK1 activities and that of JNKK2 activities could be very similar, the two kinases may play somewhat different regulatory roles in a cell-type-dependent manner.

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Differential Stabilities of Phosphorylated Response Regulator Domains Reflect Functional Roles of the Yeast Osmoregulatory SLN1 and SSK1 Proteins

Journal of Bacteriology ◽

10.1128/jb.181.2.411-417.1999 ◽

1999 ◽

Vol 181 (2) ◽

pp. 411-417 ◽

Cited By ~ 39

Author(s):

Fabiola Janiak-Spens ◽

Jeffrey M. Sparling ◽

Michael Gurfinkel ◽

Ann H. West

Keyword(s):

Response Regulator ◽

Anaerobic Respiration ◽

Bacterial Chemotaxis ◽

Signal Transduction Pathway ◽

Mitogen Activated Protein Kinase ◽

Functional Roles ◽

Regulatory Domains ◽

Mitogen Activated Protein ◽

Kinase Cascade

ABSTRACT Osmoregulation in Saccharomyces cerevisiae involves a multistep phosphorelay system requiring three proteins, SLN1, YPD1, and SSK1, that are related to bacterial two-component signaling proteins, in particular, those involved in regulating sporulation inBacillus subtilis and anaerobic respiration inEscherichia coli. The SLN1-YPD1-SSK1 phosphorelay regulates a downstream mitogen-activated protein kinase cascade which ultimately controls the concentration of glycerol within the cell under hyperosmotic stress conditions. The C-terminal response regulator domains of SLN1 and SSK1 and full-length YPD1 have been overexpressed and purified from E. coli. A heterologous system consisting of acetyl phosphate, the bacterial chemotaxis response regulator CheY, and YPD1 has been developed as an efficient means of phosphorylating SLN1 and SSK1 in vitro. The homologous regulatory domains of SLN1 and SSK1 exhibit remarkably different phosphorylated half-lives, a finding that provides insight into the distinct roles that these phosphorylation-dependent regulatory domains play in the yeast osmosensory signal transduction pathway.

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