Heterothallism in fungi
·
If fungi require 2 different strains mycelium to form zygospores
it is called heterothallic fungi.
Is
all fungi are heterothallic
- · No, there are basically 2 types of fungi.one heterothallic that needs different nature mycelium to produce zygospore.
- · And another is homothallic that do not need different nature mycelium.
- · The mycelium developed from single spore are compatible for each other.
- · They can make zygospores on hyphae of a single mycelium.
About
heterothallic fungi
·
The
2 different mycelium are morphological similar but physiological and sexual
different.
·
The
term + and – for two type of strains.
History
- · While studying mucorales- Blakeslee found that some species develop zygospores Independtly ,whereas some (like m.mucedo)produce zygospores in the presence of mass of mycelium.
- · The 2 mycellium of mucedo arising from different spores are nessery for the production of zygospores and also different in strains.
- · These mycelium were morphological similar but not physiological and sexual.
Further,
Work on heterothallism and homothallism by
raper proved there is
“no absolute
separation of sex”
4 type of mycellim in achlya bisexualis
are found by them-
1- Pure male
2- predominetly male(can make oogonia)
3- Pure female
4- Predominantly female ( can make
antherdia)
5- But none of them able to make
zygospores alone.
·
Each
needs one of three .
·
These
type of heterothallism called- gynandromictic.
Hormones
·
These
are some chemical that govern sexual process that are called hormones.
·
Raper
named them A, B, C, D.
·
One
of them is sirenin that is isolated from allomyces .
·
Sirenin
is responsible to attract male gametes.
Type of heterothallism
1-morphological heterothallism
2- Physiological heterothallism
Morphological heterothallism
·
When
one can distinguish the male and female sex organ by its structure or
morphology.
Physiological
heterothallism
- · Reproduction place by physiological different hyphae.
- · Also known as haploid incompatibility.
1. 2 allele
2. Multiple allele
2
allele heterothallism
- · Nuclei of both mating types are genetically different.
- · Sexual compatibility is controlled by genetic factor. “A” , “a”.
- · Both factors are present in different chromatid of chromosomes.
- · Due to dominance of “A” over “a” they also represented by “+” and “-“.
- · At meoisi they got seprate with chromatid.
- · Spores formed with on “+” allele and another spore formed of “–“ allele.
- · Spore with + allele give rise to + mycelium and – to – mycelium.
- · Only “+” and “-“ are compatible together.
To be continue…..
