title: Transcriptome Analysis of a Ustilago maydis ust1 Deletion Mutant Uncovers Involvement of Laccase and Polyketide Synthase Genes in Spore Development.
abstract: Ustilago maydis, causal agent of corn smut disease, is a dimorphic fungus alternating between a saprobic budding haploid and an obligate pathogenic filamentous dikaryon. Maize responds to U. maydis colonization by producing tumorous structures, and only within these does the fungus sporulate, producing melanized sexual teliospores. Previously we identified Ust1, an APSES (Asm1p, Phd1p, Sok2p, Efg1p, and StuAp) transcription factor, whose deletion led to filamentous haploid growth and the production of highly pigmented teliospore-like structures in culture. In this study, we analyzed the transcriptome of a ust1 deletion mutant and functionally characterized two highly upregulated genes with potential roles in melanin biosynthesis: um05361, encoding a putative laccase (lac1), and um06414, encoding a polyketide synthase (pks1). The Δlac1 mutant strains showed dramatically reduced virulence on maize seedlings and fewer, less-pigmented teliospores in adult plants. The Δpks1 mutant was unaffected in seedling virulence but adult plant tumors generated hyaline, nonmelanized teliospores. Thus, whereas pks1 appeared to be restricted to the synthesis of melanin, lac1 showed a broader role in virulence. In conclusion, the ust1 deletion mutant provided an in vitro model for sporulation in U. maydis, and functional analysis supports the efficacy of this in vitro mutant analysis for identification of genes involved in in planta teliosporogenesis.
authors.forename: Emir
authors.initials: E
authors.lastname: Islamovic
authors.forename: María D
authors.initials: MD
authors.lastname: García-Pedrajas
authors.forename: Nadia
authors.initials: N
authors.lastname: Chacko
authors.forename: David L
authors.initials: DL
authors.lastname: Andrews
authors.forename: Sarah F
authors.initials: SF
authors.lastname: Covert
authors.forename: Scott E
authors.initials: SE
authors.lastname: Gold
mesh_terms: D002473:Cell Wall / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D020869:Gene Expression Profiling; D042845:Laccase / Q000235:genetics* / Q000378:metabolism; D008954:Models, Biological; D020411:Oligonucleotide Array Sequence Analysis; D010858:Pigmentation; D010935:Plant Diseases / Q000382:microbiology*; D048630:Polyketide Synthases / Q000235:genetics* / Q000378:metabolism; D036226:Seedlings / Q000382:microbiology; D017384:Sequence Deletion; D013172:Spores, Fungal; D059467:Transcriptome; D014588:Ustilago / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity; D014774:Virulence; D003313:Zea mays / Q000382:microbiology*
chemical_list: D005656:Fungal Proteins; D048630:Polyketide Synthases; D042845:Laccase