Dr. James W. Kronstad

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We are interested in several aspects of fungal biology including pathogenesis, morphogenesis, infection-specific gene expression and self versus nonself recognition (mating). The fungal species that we are studying include the cereal pathogens Ustilago maydis and Ustilago hordei. These basidiomycete fungi are highly amenable to molecular genetic experimentation and cause dramatic diseases on maize and barley, respectively. We are also using the basidiomycete Cryptococcus neoformans to explore fungal pathogenesis. This fungus is an opportunistic pathogen of immunocompromised humans. The following projects are underway in the laboratory.

1. U. maydis and U. hordei have fascinating mating systems that involve genes at two genetic loci called a and b. The a locus encodes pheromones and pheromone receptors that mediate recognition between mating partners. The b locus encodes homeodomain proteins that control a switch from budding to filamentous growth. We are currently characterizing the b proteins and exploring the differences in the genomic organization of the mating type genes in the two species. The a and b genes are on separate chromosomes in U. maydis and they are linked together on the same chromosome to create a single MAT locus in U. hordei. Surprisingly, we have recently shown that the MAT locus is approximately 500 kb in size in U. hordei making it the largest mating-type locus characterized in fungi to date.

2. We have also been characterizing the role of the cAMP signal transduction pathway in the control of morphogenesis and pathogenesis for U. maydis and C. neoformans. For U. maydis, we have found that mutants defective in the cAMP pathway are altered in cell shape and virulence. For example, mutants defective in adenylate cyclase or in cAMP dependent protein kinase (PKA) no longer grow by budding and instead display constitutive filamentous growth. In contrast, cells defective in the regulatory subunit of PKA display a multiple budding phenotype. We are currently identifying genes encoding downstream targets of PKA; some of these genes are required for growth and sporulation in host tissue.

3. We have initiated a genome-wide analysis of gene expression in C. neoformans. This work is in collaboration with the Genome Sequence Centre in Vancouver and is supported by a Scholar Award from the Burroughs Wellcome Fund. We are employing the technique of serial analysis of gene expression (SAGE) to examine the transcriptomes of serotype A and D strains. Our initial experiments are focused on comparisons of transcipt profiles as a function of temperature (to examine thermotolerance) and as a function of growth in the host. The latter experiments will identify genes whose transcripts are up or down regulated during infection. This work will lead to a detailed view of gene expression during adaptation of the fungus to the host environment. To support the gene expression work, we have also participated in five genome sequencing projects for C. neoformans. We have contributed physical maps and we sequenced the genome of one strain in Vancouver (with funding from Genome Canada).

Hu, G., Cheng, P.-Y., Sham, A., Perfect, J. R. and Kronstad, J.W. Metabolic adaptation in Cryptococcus neoformans during early murine pulmonary infection. Mol. Microbiol . In Press. (2008).

Bartlett KH, Kidd SE, Kronstad JW. The Emergence of Cryptococcus gattii in British Columbia and the Pacific Northwest. Curr Infect Dis Rep 10(1):58-65. (2008).

Jung WH, Sham A, Lian T, Singh A, Kosman DJ, Kronstad JW. Iron source preference and regulation of iron uptake in Cryptococcus neoformans. PLoS Pathog 4(2):e45. (2008).

Jung WH, Kronstad JW. Iron and fungal pathogenesis: a case study with Cryptococcus neoformans. Cell Microbiol 10(2):277-84. (2008).

Hu G, Liu I, Sham A, Stajich JE, Dietrich FS, Kronstad JW. Comparative hybridization reveals extensive genome variation in the AIDS-associated pathogen Cryptococcus neoformans. Genome Biol 9(2):R41. (2008).

Xu J, Saunders CW, Hu P, Grant RA, Boekhout T, Kuramae EE, Kronstad JW, Deangelis YM, Reeder NL, Johnstone KR, Leland M, Fieno AM, Begley WM, Sun Y, Lacey MP, Chaudhary T, Keough T, Chu L, Sears R, Yuan B, Dawson TL. Dandruff-associated Malassezia genomes reveal convergent and divergent virulence traits shared with plant and human fungal pathogens. Proc Natl Acad Sci U S A 104(47):18730-5. (2007).

Kronstad JW. Self-fertility: the genetics of sex in lonely fungi. Curr Biol 17(19):R843-5. (2007).

Kidd SE, Chow Y, Mak S, Bach PJ, Chen H, Hingston AO, Kronstad JW, Bartlett KH. Characterization of environmental sources of the human and animal pathogen Cryptococcus gattii in British Columbia, Canada, and the Pacific Northwest of the United States. Appl Environ Microbiol 73(5):1433-43. (2007).

Hu G, Steen BR, Lian T, Sham AP, Tam N, Tangen KL, Kronstad JW. Transcriptional regulation by protein kinase A in Cryptococcus neoformans. PLoS Pathog 3(3):e42. (2007).

Tangen KL, Jung WH, Sham AP, Lian T, Kronstad JW. The iron- and cAMP-regulated gene SIT1 influences ferrioxamine B utilization, melanization and cell wall structure in Cryptococcus neoformans. Microbiology 15329-41. (2007).

Kidd SE, Bach PJ, Hingston AO, Mak S, Chow Y, MacDougall L, Kronstad JW, Bartlett KH. Cryptococcus gattii dispersal mechanisms, British Columbia, Canada. Emerg Infect Dis 13(1):51-7. (2007).

Klose J, Kronstad JW. The multifunctional beta-oxidation enzyme is required for full symptom development by the biotrophic maize pathogen Ustilago maydis. Eukaryot Cell 5(12):2047-61. (2006).

Kämper J, Kahmann R, Bölker M, Ma LJ, Brefort T, Saville BJ, Banuett F, Kronstad JW, Gold SE, Müller O, Perlin MH, Wösten HA, de Vries R, Ruiz-Herrera J, Reynaga-Peña CG, Snetselaar K, McCann M, Pérez-Martín J, Feldbrügge M, Basse CW, Steinberg G, Ibeas JI, Holloman W, Guzman P, Farman M, Stajich JE, Sentandreu R, González-Prieto JM, Kennell JC, Molina L, Schirawski J, Mendoza-Mendoza A, Greilinger D, Münch K, Rössel N, Scherer M, Vranes M, Ladendorf O, Vincon V, Fuchs U, Sandrock B, Meng S, Ho EC, Cahill MJ, Boyce KJ, Klose J, Klosterman SJ, Deelstra HJ, Ortiz-Castellanos L, Li W, Sanchez-Alonso P, Schreier PH, Häuser-Hahn I, Vaupel M, Koopmann E, Friedrich G, Voss H, Schlüter T, Margolis J, Platt D, Swimmer C, Gnirke A, Chen F, Vysotskaia V, Mannhaupt G, Güldener U, Münsterkötter M, Haase D, Oesterheld M, Mewes HW, Mauceli EW, DeCaprio D, Wade CM, Butler J, Young S, Jaffe DB, Calvo S, Nusbaum C, Galagan J, Birren BW. Insights from the genome of the biotrophic fungal plant pathogen Ustilago maydis. Nature 444(7115):97-101. (2006).

Jung WH, Sham A, White R, Kronstad JW. Iron regulation of the major virulence factors in the AIDS-associated pathogen Cryptococcus neoformans. PLoS Biol 4(12):e410. (2006).

Bakkeren G, Jiang G, Warren RL, Butterfield Y, Shin H, Chiu R, Linning R, Schein J, Lee N, Hu G, Kupfer DM, Tang Y, Roe BA, Jones S, Marra M, Kronstad JW. Mating factor linkage and genome evolution in basidiomycetous pathogens of cereals. Fungal Genet Biol 43(9):655-66. (2006).

Boyce KJ, Kretschmer M, Kronstad JW. The vtc4 gene influences polyphosphate storage, morphogenesis, and virulence in the maize pathogen Ustilago maydis. Eukaryot Cell 5(8):1399-409. (2006).

Lian T, Simmer MI, D'Souza CA, Steen BR, Zuyderduyn SD, Jones SJ, Marra MA, Kronstad JW. Iron-regulated transcription and capsule formation in the fungal pathogen Cryptococcus neoformans. Mol Microbiol. 55(5713):1452-1472. (2005).

Loftus BJ, Fung E, Roncaglia P, Rowley D, Amedeo P, Bruno D, Vamathevan J, Miranda M, Anderson IJ, Fraser JA, Allen JE, Bosdet IE, Brent MR, Chiu R, Doering TL, Donlin MJ, D'Souza CA, Fox DS, Grinberg V, Fu J, Fukushima M, Haas BJ, Huang JC, Janbon G, Jones SJ, Koo HL, Krzywinski MI, Kwon-Chung JK, Lengeler KB, Maiti R, Marra MA, Marra RE, Mathewson CA, Mitchell TG, Pertea M, Riggs FR, Salzberg SL, Schein JE, Shvartsbeyn A, Shin H, Shumway M, Specht CA, Suh BB, Tenney A, Utterback TR, Wickes BL, Wortman JR, Wye NH, Kronstad JW, Lodge JK, Heitman J, Davis RW, Fraser CM, Hyman RW. The genome of the basidiomycetous yeast and human pathogen Cryptococcus neoformans Science 307(5713):1321-1324. (2005).

Klose J, de Sá MM, Kronstad JW. Lipid-induced filamentous growth in Ustilago maydis. Mol Microbiol 52(3):823-35. (2004).

Linning R, Lin D, Lee N, Abdennadher M, Gaudet D, Thomas P, Mills D, Kronstad JW, Bakkeren G. Marker-based cloning of the region containing the UhAvr1 avirulence gene from the basidiomycete barley pathogen Ustilago hordei. Genetics 166(1):99-111. (2004).