Ashbya gossypii

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Ashbya gossypii
Fluorescence microscope image of the mycelium of Ashbya gossypii (cell nuclei marked)

Fluorescence microscope image of the mycelium of Ashbya gossypii (cell nuclei marked)

Systematics
Subdivision : Saccharomycotina
Class : Saccharomycetes
Order : Real yeast (Saccharomycetales)
Family : Saccharomycetaceae
Genre : Eremothecium
Type : Ashbya gossypii
Scientific name of the  genus
Eremothecium
Borzì
Scientific name of the  species
Ashbya gossypii
( SF Ashby & W. Nowell ) Guillierm

Ashbya gossypii (also Eremothecium gossypii ) is a mold that isclosely relatedto baker's yeast . It was first described by Ashby and Nowell in 1926as a pathogen in cotton plants , in which itcauses what is known as stigmatomycosis . The disease affects the development of hair cells in the seed pods of cotton and can betransmittedto citrus fruits , which then dry out and collapse ( dry rot ). A. gossypii is a natural overproducer of riboflavin (vitamin B 2 ), which is why it became of industrial interest.

description

Growth, development and morphology

Development from spore to mature mycelium in A. gossypii. (With kind permission from Dr. Philipp Knechtle)
a) Non-germinating spore
b) Isotropic growth phase in the seminal vesicle
c) Unipolar seedling
d) Second germ tube appears
e) Side branches and creation of the septum
f) Apical branching in mature hyphae

The life cycle of A. gossypii begins with the uniform ( isotropy ) growth of the haploid spore on all sides , their germination. This is followed by apical growth, which produces two germ tubes one after the other on opposite sides of the germinal vesicle. Additional axes are formed when branching off laterally in young mycelium. Maturation is characterized by apical branches (splitting of tips) and a dramatic increase in growth rate (up to 200 μm / h at 30 ° C), which enables A. gossypii to fill an 8 cm diameter Petri dish in about 7 days. The sporulation is likely caused by food deprivation and leads to contraction of the septum , cytokinesis and subsequent secretion of the sporangia , which can contain up to eight haploid spores. The hyphae themselves are generally divided by septa, which initially appear as a ring that allows the transfer of nuclear material; later the appearance of the septa changes to a closed disc. Each hyphae compartment contains about eight cell nuclei .

Karyotype and genome

The genetic information of A. gossypii is in the cell nucleus in 7 autosomes and in the nucleus of the mitochondria . The genome of the ATCC 10895 strain was completely analyzed for the first time in 2004; it consists of 9 million base pairs and an estimated 4,750 genes . It is thus the smallest known genome of a free-living eukaryote . Ninety percent of the genes in A. gossypii are both homologous and in the same order ( syntany ) as in Saccharomyces cerevisiae . The ancestor of both organisms lived 100 million years ago. While A. gossypii changed only slightly, a gene duplication occurred in the subsequent evolution of baker's yeast .

pathology

A. gossypii and two other fungi that cause stigmatomycosis ( Eremothecium coryli , Aureobasidium pullulans ) made it almost impossible to cultivate cotton in some subtropical regions in the first half of the 20th century . Only the control of the spore-transmitting insect species Dysdercus suturellus and Antestia angulosa was able to prevent the cotton from becoming infected.

A. gossypii as a model organism

Due to its small and also haploid genome and existing efficient methods for gene targeting , A. gossypii is recognized as a model organism , especially for studying the growth of long and multinucleated fungal cells. It is widely believed that a better understanding of hyphae growth will enable the development of novel fungicides . Ashbya gossypii is particularly promising as a model organism due to the high degree of conservation of the gene sequence ( syntany ) between the genomes of A. gossypii and Saccharomyces cerevisiae .

Taxonomic position

In more recent works, the genera Ashbya , Holleya , and Nematospora are synonymous with Eremothecium . The four genera are characterized by needle-shaped ascospores that can be straight or curved. The taxa are pathogenic in various plant species and Ashbya and Eremothecium are used worldwide for the production of riboflavin. Phylogenetic analyzes of ribosomal RNA and DNA in the 1990s agree that the four species are congeners .

literature

  • P. Philippsen, A. Kaufmann, HP Schmitz: Homologues of yeast polarity genes control the development of multinucleated hyphae in Ashbya gossypii . In: Curr Opin Microbiol . tape 8 , no. 4 , 2005, p. 370-377 , doi : 10.1016 / j.mib.2005.06.021 , PMID 16023404 .
  • AS Gladfelter: Nuclear anarchy: asynchronous mitosis in multinucleated fungal hyphae. In: Curr Opin Microbiol . tape 9 , no. 6 , 2006, p. 547-552 , doi : 10.1016 / j.mib.2006.09.002 , PMID 17045513 .

Web links

Individual evidence

  1. ^ SF Ashby, W. Nowell: The Fungi of Stigmatomycosis. In: Ann Bot . os-40, no. 1 , 1926, pp. 69-84 ( oxfordjournals.org ).
  2. ↑ KP Stahmann, JL Revuelta, H. Seulberger: Three biotechnical processes using Ashbya gossypii, Candida famata, or Bacillus subtilis compete with chemical riboflavin production . In: Appl. Microbiol. Biotechnol. tape 53 , no. 5 , May 2000, pp. 509-516 , PMID 10855708 .
  3. ^ A. Kaufmann: Polarized growth and septation in the filamentous ascomycete "Ashbya gossypii" analyzed by live cell imaging. In: edoc.unibas.ch. Univ. Basel, February 13, 2009, accessed on February 13, 2011 (PhD Thesis, University of Basel, Faculty of Science).
  4. ^ NCBI entry Genome Project
  5. ↑ Integr8 entry
  6. ↑ a b FS Dietrich, S. Voegeli, S. Brachat, A. Lerch, K. Gates, S. Steiner, C. Mohr, R. Pohlmann, P. Luedi, S. Choi, RA Wing, A. Flavier, TD Gaffney, P. Philippsen: The Ashbya gossypii genome as a tool for mapping the ancient Saccharomyces cerevisiae genome. In: Science . tape 304 , no. 5668 , 2004, p. 304-307 , doi : 10.1126 / science.1095781 , PMID 15001715 .
  7. ^ LR Batra: Nematosporaceae (Hemiascomycetidae): taxonomy, pathogenicity, distribution, and vector relations . In: United States. Dept. of Agriculture (Ed.): Technical bulletin . tape 1469 , 1973.
  8. ^ CP Kurtzman, JW Fell: The yeasts: a taxonomic study . Elsevier, Amsterdam / New York 2000, ISBN 0-444-81312-8 , pp. 204-208 .
  9. ↑ CP Kurtzman: Relationships among the genera Ashbya, Eremothecium, Holleya and Nematospora determined from rDNA sequence divergence . In: Journal of Industrial Microbiology . tape 14 , no. 6 , June 1, 1995, pp. 523-530 , doi : 10.1007 / BF01573968 , PMID 7662294 .
  10. ↑ R. Messner, H. Prillinger, M. Ibl, G. Himmler: Sequences of ribosomal genes and internal transcribed spacers move three plant parasitic fungi, Eremothecium ashbyi, Ashbya gossypii, and Nematospora coryli, towards Saccharomyces cerevisiae . In: J Gen. Appl. Microbiol. tape 41 , no. 1 , 1995, p. 31-42 .