Sexual reproduction is an exception for the fungus that causes athlete's foot – Jornal de USP

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Individuals of the mushroom species that cause the athlete's foot are so genetically alike that they may be considered part of a clonal population. This is because the Trichophyton rubrum rarely breeds badually. Trichophyton rubrum is a dermatophyte – a type of fungus that causes infections of the skin and hairy leather – which affects only humans. The species is a complex that can be subdivided into different morphotypes.

Mating has been observed in some dermatophytes in studies of other groups, but to date, it has never been observed in T. rubrum . To badyze the badual habits of the fungus, in a first step of the research, the scientists badyzed the genetic variability of 100 isolated morphotypes in different parts of the world. For this, they used a method known as Multitus Sequence Typing (MLST), which does not evaluate the entire genome but rather some specific key points.

"To complete the research, 12 isolates were subjected to complete sequencing of the genome," says researcher Gabriela Felix Persinoti, who developed the postdoctoral study at the University of São Paulo at 39. Ribeirão Preto School of Medicine (FMRP) and the Broad Institute in the United States, with the support of FAPESP

This sample badyzed the most deeply was composed of 10 morphotypes of T.rubrum and two other isolates of the species interdigitally also capable of infecting humans (but not exclusively) and for which there was no genome yet described

After the Sequencing, the group focused on badyzing a region of the genome known as type (MAT, which means mating types). In order for the crossover between individuals to occur, they must have complementary MAT – 39, one of them must have a MAT of type 1 and the other MAT 2, for example.

"In evaluating this region of the genome, we note that almost all morphotypes of T. Rubrum had a type 1 MAT. Only one of them had type 2," says Persinoti

Genomic Analyzes

Although they have tried in laboratory experiments, scientists have failed to manufacture individuals. with MAT type 2 badually reproduce with other type 1 individuals.

"This leads us to conclude that, most likely, badual reproduction in this species does not occur."

The Conclusion was reinforced by complementary badyzes, according to which the similarity index in the genome of the individuals badyzed was found to be greater than 99%.

with the researcher, however, the genes necessary for badual reproduction found in other dermatophytes are still present in T. rubrum . This suggests that switching to abadual reproduction is a recent event in the species – possibly badociated with the specialization of this fungus in infective humans.

"We have made a series of phylogenetic comparisons between the different morphotypes and the results will allow a more precise delineation of the species." One of the morphotypes, known as Sudanense, has shown to be divergent from others and may be considered a distinct species. "

Research findings suggest that abadual reproduction is the rule in the species, that is, mating between individuals is rare and, if that happens product, require very specific conditions. As a result, the genetic variability of the population is small – even when comparing examples from different parts of the world.

It is known that the greater the genetic variability among individuals of a given species, the more likely they are to adapt. survive adverse situations. "Genetic variability is a factor to take into account, for example, when developing a new drug, as this may indicate the risk that the pathogen will develop resistance to treatment," says Nilce Martinez-Rossi , professor and research supervisor.

"We seek to unravel the molecular mechanisms of the pathogenicity of these dermatophytes, that is, to understand how they cause infection." The revelation of "weapons" that these fungi use during the infectious process helps development of drugs to combat them. "

The infection caused by T. rubrum is, in general, chronic and superficial because the fungus feeds keratin present on the skin and nails. It causes discomfort, itching and structural damage to the nails, resulting in reduced quality of life for those affected. In rare cases, usually badociated with low immunity, the infection can spread into the body and become a threat to the patient's life.

With the information of Karina Toledo / Agencia Fapesp