The USP group studies the reproductive habits of the fungus that causes the athlete's foot

Karina Toledo | Agência FAPESP – The badual habits of Trichophyton rubrum – the fungus that causes athlete's foot and other types of fungus skin and nails – are the subject of research published by Brazilian scientists and collaborators from other countries in Genetics magazine

The results of the research suggest that abadual reproduction is the rule in the species, that is to say that mating between individuals is not common and, if it occurs, requires very specific conditions. As a result, the genetic variability of the population is low – even comparing examples from different parts of the world.

"We can conclude that it is a clonal population, that is to say that there is practically no crossbreeding between individuals. . Thus, few variations are generated in the genome, "said Gabriela Felix Persinoti, the first author of the article, conducted with a FAPESP postdoctoral fellowship

As explained by Nilce Martinez-Rossi, professor at the Faculty of Medicine of Ribeirão Preto of the University of São Paulo (FMRP-USP) and supervisor of research, understanding how these fungi reproduce is a knowledge of basic science, but without which one can not advance in terms applied research

"Genetic variability is a factor to consider, for example, when a new drug is being developed, as it may indicate the risk that the pathogen will develop resistance to treatment," said Martinez-Rossi

.individuals of a given species, the more likely they are to adapt and survive adverse situations.

The work of Persinoti int gre one of the lines of research coordinated by Martinez-Rossi at the USP, whose goal is to understand how dermatophyte fungi – able to cause infections on the skin, the fingernails of animals and humans – interact with their hosts. The other line coordinated by the researcher seeks to understand the mechanisms of drug resistance of this same group of microorganisms.

According to the professor, T. rubrum is a species of dermatophyte that exclusively infects humans. In general, it is a chronic and superficial infection, because the fungus feeds on the 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.

"We seek to discover the molecular mechanisms of the pathogenicity of these dermatophytes." The revelation of the "weapons" that these fungi use during the infectious process helps the development of drugs to combat them, "said Martinez-Rossi, who coordinates a thematic project funded by FAPESP

The research was conducted by Persinoti in the Christina Institute of the Broad Institute – related to the Mbadachusetts Institute of Technology (MIT) and Harvard University in the United States – during an internship abroad with the support of FAPESP

Genomic badyzes

As the authors explained in the article, the species Trichophyton rubrum is a complex which can be subdivided into different morphotypes In the first stage of the research, Persinoti and his colleagues badyzed the genetic variability of 100 isolated morphotypes in different world with a method known as multi-locus sequence typing (MLST), which does not evaluate the entire genome but rather some specific key points.

"To complete the search, 12 isolates were subjected to complete genome sequencing." The most deeply badyzed sample included 10 morphotypes of T.rubrum and two other T. interdigitale isolates, also capable of infecting humans (but not exclusively) and for which no genome was found. Had been described.

sequencing, the group focused on the badysis of a region of the genome known as the type of mating (MAT). In order for the crossing to occur between individuals, they must have complementary MAT – one of them must have MAT type 1 and other MAT type 2, for example.

Mating has already been observed in some dermatophytes "

" When we evaluated this region of the genome, we noticed that almost all T. rubrum morphotypes had type 1 MAT. of them presented type 2 "

Although they tried in laboratory experiments, scientists were unable to isolate with type 2 MAT badually reproduced 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 revealed 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, suggesting that the switch to abadual reproduction is a recent event in the species – possibly badociated with the specialization of this fungus in the infecting human

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

The entire genome badysis illustrates the overall structure of the clonal population of the ubiquitous dermatophyte pathogen Trichophyton rubrum, by Gabriela F. Persinoti, Nilce M. Martinez-Rossi, Diego A. Martinez and others, can be read at: www.genetics.org/content/208/4/1657.