The machinery for cell polarity, cell morphogenesis, and the cytoskeleton in the Basidiomycete fungus Ustilago maydis—A survey of the genome sequence☆

Abstract

Ustilago maydis, a Basidiomycete fungus that infects maize, exhibits two basic morphologies, a yeast-like and a filamentous form. The yeast-like cell is elongated, divides by budding, and the bud grows by tip extension. The filamentous form divides at the apical cell and grows by tip extension. The repertoire of morphologies is increased during interaction with its host, suggesting that plant signals play an important role in generation of additional morphologies. We have used S. cerevisiae and S. pombe genes known to play a role in cell polarity and morphogenesis, and in the cytoskeleton as probes to survey the U. maydis genome. We have found that most of the yeast machinery is conserved in U. maydis, albeit the degree of similarity varies from strong to weak. The U. maydis genome contains the machinery for recognition and interpretation of the budding yeast axial and bipolar landmarks; however, genes coding for some of the landmark proteins are absent. Genes coding for cell polarity establishment, exocytosis, actin and microtubule organization, microtubule plus-end associated proteins, kinesins, and myosins are also present. Genes not present in Saccharomyces cerevisiae and Schizosaccharomyces pombe include a homologue of mammalian Rac, a hybrid myosin-chitin synthase, and several kinesins that exhibit more similarity to their mammalian counterparts. We also used the U. maydis genes identified in this analysis to search other fungal and other eukaryotic genomes to identify the closest homologues. In most cases, not surprisingly, the closest homologue is among filamentous fungi, not the yeasts, and in some cases it is among mammals.

Hyphal and cytoskeleton polarization in Tuber melanosporum: A genomic and cellular analysis

“…Our knowledge of the molecular components involved in polarized growth in S. cerevisiae, S. pombe or A. nidulans and other filamentous fungi has improved rapidly over the past few years ( Banuett et al, 2008;Borkovich et al, 2004;Fischer et al, 2008;Seiler and Plamann, 2003, Steinberg, 2007aand Virag and Harris, 2006. Nevertheless, the comparison of mechanisms in different organisms shows that our understanding of the processes involved is not yet complete.…”

“…The signal from different Rho proteins in fact converges on the Bni1 formin, a polarisome component, to control actin organization ( Sheu et al, 1998). The components Bni1, Spa2, Bud6-Aip3 of the polarisome complex were found in the T. melanosporum genome, while Pea2 (present in S. cerevisiae, Pichia stipitis) was absent, as in Ustilago maydis ( Banuett et al, 2008), A. nidulans ( Harris and Momany, 2004) and N. crassa ( Borkovich et al, 2004).…”

“…Three groups have been identified: two genes encoding the tubulin α-chain and two genes encoding the tubulin β-chain, in addition to a tubulin γ-chain gene, exactly as in S. cerevisiae, A. nidulans and other filamentous fungi ( Oakley, 2004). Likewise, one tubulin α-chain, two tubulin β-chain and one γ-chain genes are present in U. maydis ( Banuett et al, 2008).…”

“…The aim of this paper was to explore the Tuber melanosporum genome sequence by searching for gene homologs known to play crucial roles in both morphogenesis and/or polarity establishing and maintenance in yeasts ( Drees et al, 2001) and in filamentous fungi ( Banuett et al, 2008 andBorkovich et al, 2004).…”

“…The examined gene/protein networks were divided on the bases of the roles of the single components, that are known in other fungi (S. cerevisiae, and other filamentous fungi; Banuett et al, 2008;Borkovich et al, 2004;Harris et al, 2009). …”