Can mushrooms tell us the evolution of two sexes?

Mushrooms do not clearly divide males but they have sex differences. A new discovery by Duke University Medical Center has revealed some of the earliest forms of fungi that contain evolutionary clues between two sexes in higher animals, including distant relatives of mushrooms - is our species.

The team led by Dr. Joseph Heitman separated the gene that regulates sex from an ancient fungus known as Phycomyces blakesleenus . The results were published on January 10, 2008 in Nature .

Mushrooms do not have complete sex chromosomes like the two X and Y chromosomes that regulate sexual characteristics in humans. Instead, the fungus has DNA called ' mating mode ' that sequences in order to determine sex. The gene that regulates mating is found in some higher-grade fungi and unusually diverse. The difference in this gene fragment in the fungi with them makes scientists wonder about their evolution.

Heitman's team theorized that the order of sex regulation genes found in the earliest forms of fungi helps to explore the ancient structure of the gene segment that regulates mating and acts as a chemical. molecular jelly.

Heitman said: 'The fungus is a very good model of sex evolution in humans because the gene sequence for identifying the gender in the fungus is a miniature version of the sex-regulated region on the chromosome. calculated in humans'.

Phycomyces (Photo: Wikimedia.org)

To identify the mating method in Phycomyces, the researchers used computers to compare the mating rule set on the genome in another fungus and then compare the genetic map. Heitman said: 'We have used a protein comparison method in some fungal species and determine which proteins occur in all species'.

Based on the structure of DNA, scientists can isolate two versions of the gene that regulates sex they call sexM and sexP . The fungus that carries one of these two genes can mate with the other species of the opposite gene.

Both versions of sexM and sexP gene encode for a protein group called HMG (highly flexible group) that leads to gender differences in any process. This protein is quite similar to a protein called SRY encoded by the Y chromosome in humans . The Y chromosome causes the fetus to develop male sex. Heitman argues that this similarity indicates that HMG protein domain has marked the beginning of sex evolution in both fungi and humans.

Rhizopus oryzae mushroom
(Photo: Adelaide.edu.au)

Heitman's research group suggested that the gene sexM and sexP, which is a homogenous gene, underwent a reverse mutation. Their new versions evolved into two genes that regulate different sexes. A similar process also occurs with chromosomes that regulate male sex Y in humans.

Heitman hopes to identify the sex-regulated region in another fungus called Rhizopus oryzae in order to gain a deeper understanding of the HMG domain's role in regulating sex differences. The gene of Rhizopus may have evolved and chemically changed in such a way that the sex gene of Phycomyces cannot.

Dr. Alexander Idnurm, the lead author of the new study recently appointed an assistant professor at the University of Missouri - Kansas City, explains: 'Rhizopus species can be used to understand the effects of some genes. certain fungi are known less in the way we use lab rats to understand the effects of genes in humans'.

Another mystery that makes it difficult for Heitman is that some new fungal species do not have HMG protein domains. He thinks these proteins may have been replaced by some alternative transcription factor that is also proteins that can turn on or turn off sex-regulated genes.