A. Bernardo Carvalho

A. Bernardo Carvalho

Fellow: Awarded 2011

Field of Study: Organismic Biology & Ecology

Competition: Latin America & Caribbean

One of the world’s leading researchers on the evolution of Y chromosomes and an active participant in both the Drosophila and Rhodnius prolixus genome projects, Antonio Bernardo Carvalho is an Associate Professor in the Genetics Department at the Universidade Federal do Rio de Janeiro, Brazil (UFRJ), a position he has held since 1991. He was educated at UFRJ, receiving his bachelor’s degree in Biology in 1985 and his master’s (1989) and doctoral (1994) degrees in Genetics there, under the supervision of Dr. Louis Bernard Klaczko, and was appointed to its faculty before completing his Ph.D.

During the late 1990s, he, along with his students and his Ph.D. supervisor Dr. Klaczko, made two important research advances. They experimentally confirmed “Fisher’s Principle,” which postulated that natural selection would along time equalize the number of males and females in natural populations. They also devised an explanation for a non-neutral Y-polymorphism they found in two natural populations of Drosophila mediopunctata, in which up to 20 percent of the Y chromosomes are able to suppress the “killing effect” of SR chromosomes; at the time it was believed that Y chromosomes could only harbor neutral polymorphisms. Their findings were published in the scientific journals Genetics (1997, 1998) and Heredity (1997).

From 1998 to 2000, he worked in the lab of Andrew Clark at Penn State University under the aegis of a Pew Latin American Fellowship; only about ten Latin American biomedical researchers receive this fellowship annually. The original project for which he received the fellowship was to obtain a molecular marker that would facilitate the identification of Y chromosomes of D. mediopunctata that are able to suppress the killing effect of SR chromosomes. This work was partially hampered by the gigantic introns of the Drosophila Y-linked genes, which were discovered by other Drosophila researchers around that time. This nuisance led him to wonder why the introns of Y-linked genes in Drosophila are so large, and then to theorize and confirm that, as he explained, “large introns [persisted] in the Y because this chromosome does not recombine, and it is known that Natural Selection is much less efficient in the absence of recombination.” He and Andrew Clark published this finding in Nature (vol. 41, 1999). His work on the D. mediopunctata Y chromosome also raised his interest on the Y chromosome genes of Drosophila, about which very little was known. For example, even in the intensively studied model organism D. melanogaster, at that time only one protein-coding Y linked gene was known at the molecular level. The D. melanogaster genome sequence was announced in 2000, but surprisingly no additional Y-linked gene was found. Dr. Carvalho decided to hunt them, and quickly found that they were present in the D. melanogaster genome assembly, but were not identified because their sequence were scattered in many pieces, due to the abundance of repetitive DNA sequences. With other members of the Clark lab, he published two papers in Proceedings of the National Academy of Sciences (2000, 2001), detailing the computer program he developed that allowed them to identify eight new genes on the Y chromosome of D. melanogaster. Even after Dr. Carvalho returned to Brazil, he continued to work in collaboration with Dr. Clark, publishing jointly authored papers on various new findings about the D. melanogaster genome and the evolution of the Y chromosome in such top-tier journals as Molecular Biology and Evolution, Genetica, Science, and Nature.

On his return to UFRJ in 2000, with monies from his Pew Fellowship and support from the National Institutes of Health (NIH-FIRCA, USA) and the Brazilian agencies CNPq and FAPERJ, he was able to purchase the necessary equipment for his lab to continue and expand on the investigations on the Drosophila Y chromosome. He further refined his methods for identifying Y-linked genes; conducted studies that called into question the long-accepted theory that the Y chromosome always originated from the degeneration of the X chromosome, and, as detailed in his 2005 article in Science (coauthored with Andrew Clark), discovered that despite certain similarities between the D. pseudoobscura and D. melanogaster their Y chromosomes have nothing in common, lending further support to the hypothesis that the Y chromosome can appear de novo and not only from degeneration of the X. Dr. Carvalho's lab also participated in the “12 Drosophila genomes project,” where his Ph.D. student Leonardo Koerich investigated the Y chromosomes. They found that, in contrast to what is observed in mammals and other organisms (and believed to be a universal pattern), the gene content of the Drosophila Y is increasing. These findings were published in Nature (Koerich et al., 2008). Leonardo's thesis also won in 2009 the prestigious Larry Sandler Award, which is given by the Genetics Society of America for the best Drosophila dissertation of the preceding year. In the next year it won the “Grande Premio CAPES de Tese 2010” as the best Brazilian Ph.D. thesis in the Biological Sciences field.

During his Guggenheim Fellowship term, Dr. Carvalho will be continuing his research on the origin and evolution of Y chromosomes and refining current methods and developing new ones for identifying the Y-linked genes in Rhodnius prolixus and other species.

In addition to mentoring students in his lab, teaching Genetics, conducting research, and publishing his findings in some of the most important journals in his field, Antonio Bernardo Carvalho has also been an invited speaker at the Gordon Conference in Molecular Evolution (2006), the Congress of the Society for Molecular Biology and Evolution (2006), the Congress of the European Society of Evolutionary Biology (2007), and the XX International Congress of Genetics (2008) in Berlin.