(also known as Ashbya gossypii
) is a filamentous
fungus or
mold closely related to
yeast, but growing exclusively in a filamentous way. It was originally isolated from
cotton as a
pathogen causing
stigmatomycosis
Stigmatomycosis is a fungal disease that occurs in a number of crops, such as cotton, soybean, pecan, pomegranate, citrus, and pistachio. It has been reported on pistachio in Greece, Iran, Russia, and is frequently a problem in California pistachi ...
by
Ashby Ashby may refer to:
People
* Ashby (surname)
* Alan la Zouche, 1st Baron la Zouche of Ashby (1267–1314), governor of Rockingham Castle and steward of Rockingham Forest, England
* Walter Ashby Plecker (1861–1947), American physician and publ ...
and
Nowell in 1926. This disease affects the development of
hair cells in cotton bolls and can be transmitted to citrus fruits, which thereupon dry out and collapse (dry rot disease). In the first part of the 20th century, and two other fungi causing stigmatomycosis (, ) made it virtually impossible to grow cotton in certain regions of the subtropics, causing severe economical losses. Control of the spore-transmitting insects
cotton stainer() and
- permitted full eradication of infections. was recognized as a natural overproducer of
riboflavin
Riboflavin, also known as vitamin B2, is a vitamin found in food and sold as a dietary supplement. It is essential to the formation of two major coenzymes, flavin mononucleotide and flavin adenine dinucleotide. These coenzymes are involved in ...
(vitamin B
2), which protects its spores against ultraviolet light. This made it an interesting organism for industries, where genetically modified strains are still used to produce this
vitamin.
as a model organism
A few years ago, became recognized as an attractive
model to study the growth of long and
multinucleate fungal cells (
hypha
A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium.
Structure
A hypha consists of one or ...
e) because of its small
genome,
haploid
Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respectively ...
nuclei, and efficient
gene targeting methods. It is generally assumed that a better understanding of filamentous fungal growth will greatly stimulate the development of novel
fungicide
Fungicides are biocidal chemical compounds or biological organisms used to kill parasitic fungi or their spores. A fungistatic inhibits their growth. Fungi can cause serious damage in agriculture, resulting in critical losses of yield, quality, ...
s. Its use as a
model organism
A model organism (often shortened to model) is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the model organism will provide insight into the workin ...
is particularly promising because of the high level of
gene order conservation (
synteny) between the
genomes of and the yeast .
Genome
The complete
sequencing
In genetics and biochemistry, sequencing means to determine the primary structure (sometimes incorrectly called the primary sequence) of an unbranched biopolymer. Sequencing results in a symbolic linear depiction known as a sequence which succ ...
and
annotation of the entire genome, as published in 2004, was initiated when a significant degree of
gene synteny was observed in preliminary studies in comparison to the genome of budding yeast, . This not only helped to improve gene annotation of , but also allowed the
reconstruction of the
evolutionary history of both organisms. and originated from a common
ancestor
An ancestor, also known as a forefather, fore-elder or a forebear, is a parent or (recursively) the parent of an antecedent (i.e., a grandparent, great-grandparent, great-great-grandparent and so forth). ''Ancestor'' is "any person from whom ...
which carried about 5000 genes.
Divergence of these two close relatives started some 100 million years ago. One branch of evolution involving up to 100 viable
genome rearrangements (
translocations
In genetics, chromosome translocation is a phenomenon that results in unusual rearrangement of chromosomes. This includes balanced and unbalanced translocation, with two main types: reciprocal-, and Robertsonian translocation. Reciprocal translo ...
and
inversions), a few million
base pair
A base pair (bp) is a fundamental unit of double-stranded nucleic acids consisting of two nucleobases bound to each other by hydrogen bonds. They form the building blocks of the DNA double helix and contribute to the folded structure of both DNA ...
changes, and a limited number of gene
deletions,
duplications and additions lead to modern with its 4718 protein-coding genes and 9.2 million base pairs (smallest genome of a free-living eukaryote yet characterized) spread over seven
chromosomes. The genome of underwent a more eventful evolution, which includes a whole-genome duplication.
Despite the long evolutionary history of the two organisms and fundamentally different ways of growth and development, the complete synteny map of both genomes reveals 95% of genes are
orthologs of genes, and 90% map within blocks of synteny (syntenic
homologs).
Growth, development and morphology
The
life cycle starts with the only known phase of
isotropic
Isotropy is uniformity in all orientations; it is derived . Precise definitions depend on the subject area. Exceptions, or inequalities, are frequently indicated by the prefix ' or ', hence ''anisotropy''. ''Anisotropy'' is also used to describe ...
growth in
wild type:
germination
Germination is the process by which an organism grows from a seed or spore. The term is applied to the sprouting of a seedling from a seed of an angiosperm or gymnosperm, the growth of a sporeling from a spore, such as the spores of fungi, fer ...
of the
haploid
Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respectively ...
spore
In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, f ...
to form a germ bubble. This is followed by
apical growth, extending two germ tubes in succession on opposing sites of the germ bubble. More axes of polarity are established with
lateral branch formation in young
mycelium. Maturation is characterized by apical branching (tip splitting) and a dramatic increase of growth speed (up to 200 μm/h at 30 °C), which enables it to cover an 8 cm
Petri dish
A Petri dish (alternatively known as a Petri plate or cell-culture dish) is a shallow transparent lidded dish that biologists use to hold growth medium in which cells can be cultured,R. C. Dubey (2014): ''A Textbook Of Biotechnology For Class- ...
of
full medium in about seven days.
Sporulation is thought to be induced by
nutrient
A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excret ...
deprivation, leading to contraction at the
septa,
cytokinesis and subsequent abscission of
sporangia which contain up to eight
haploid
Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respectively ...
spores.
Hypha
A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium.
Structure
A hypha consists of one or ...
e are compartmentalized by septa, which in young parts appear as rings that allow transfer of
nuclei and in older parts may appear as closed discs. Compartments typically contain around eight
nuclei.
References
External links
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{{Taxonbar, from=Q27061531
Saccharomycetes
Fungal plant pathogens and diseases
Cotton diseases
Fungal citrus diseases