Análise do conteúdo gênico e expressão diferencial de variantes do cromossomo B em Psalidodon (Teleostei, Characiformes)
Carregando...
Data
2022-02-21
Autores
Vidal, Mateus Rossetto [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
Cromossomos B são elementos supranumerários do genoma de eucariotos, com diversos aspectos ainda incógnitos. Apesar de sua composição pobre em genes codificadores de proteínas, a descrição de transcritos provenientes destes elementos vem alterando a visão de que são estruturas inertes no genoma. Dentre os peixes do gênero Psalidodon, uma grande diversidade desses elementos pode ser observada, com a ocorrência de micro a macro cromossomos B com diferentes morfologias. Estudos anteriores demonstram a ocorrência de pelo menos 21 genes nos cromossomos B de Psalidodon paranae e Psalidodon scabripinnis, sendo que ambas as espécies possuem maior presença de cromossomos B em fêmeas, o que sugere sua atuação nas vias de diferenciação do sexo. Desta forma, o presente estudo visou investigar o conteúdo gênico da variante BfMa de Psalidodon fasciatus para testar a hipótese de origem comum com outras variantes no gênero, bem como investigar se a presença de cromossomos B leva à expressão diferencial de genes da via de diferenciação do sexo em P. paranae. Para isso, foram coletados e analisados indivíduos de P. paranae e P. fasciatus e as análises de qPCR permitiram identificar oito genes codificadores de proteína na variante BfMa de P. fasciatus (amhr2, ccpg1, cia30, g2e3, msh4, nobox, nusap1, sbno2), sendo que seis destes já foram descritos na variante BfMb da mesma espécie. Dessa forma, é altamente provável que ambas as variantes possuam uma origem comum e se diversificaram ao ponto de perder ou adquirir genes exclusivos. Ainda, devido ao compartilhamento de cinco genes entre os cromossomos B de Psalidodon já analisados, pode-se concluir que a variante BfMa também compartilha de uma origem comum com as demais variantes do gênero ocorrida há cerca de 4 milhões de anos e que sua origem não se deu por hibridação interespecífica recente. As análises de RT-qPCR em gônadas de P. paranae mostraram a expressão diferencial de três genes em fêmeas (cyp19a1a, esr1 e nobox) e de dois em machos (dmrt1 e nobox). A subexpressão dos genes cyp19a1a e esr1 em fêmeas poderia ser reflexo de um processo de desregulação causado pelo cromossomo B, ou uma resposta do genoma A para neutralizar o genoma B, ou ainda um possível efeito funcional destes cromossomos, que levaria a uma distorção do período reprodutivo. A superexpressão do gene nobox poderia refletir a existência de um mecanismo de acúmulo destes cromossomos, determinando uma maior eficiência no processo de oogênese e um maior sucesso reprodutivo para fêmeas +B. Em machos, a superexpressão do gene dmrt1 poderia causar uma alteração do ciclo reprodutivo dos indivíduos, como já foi verificado ocorrer em P. scabripinnis por outros autores.
B chromosomes are supernumerary elements found in the genome of eukaryotes and have several aspects still unknown. Despite its poor composition in protein-coding genes, the description of transcripts from these elements has changed the view that they are inert structures in the genome. Among the fish of the genus Psalidodon, a great diversity of these elements can be observed, with the occurrence of micro to macro B chromosomes, with different morphologies. Previous studies have demonstrated the occurrence of at least 21 genes in the B chromosomes of Psalidodon paranae and Psalidodon scabripinnis, with both species having a greater presence of B chromosomes in females, which suggests their role in sex differentiation pathways. Thus, the present study aimed to investigate the gene content of the BfMa variant of Psalidodon fasciatus to test the hypothesis of a common origin with other variants in the genus, as well as to investigate whether the presence of B chromosomes leads to the different expression of genes in the differentiation pathway of the sex in P. paranae. For this, individuals of P. paranae and P. fasciatus were collected and analyzed and the qPCR analysis allowed the identification of eight protein-coding genes in the BfMa variant of P. fasciatus (amhr2, ccpg1, cia30, g2e3, msh4, nobox, nusap1, and sbno2), being that six of these have already been described in the BfMb variant of the same species. Thus, it is highly likely that both variants have a common origin and have diversified to the point of losing or acquiring unique genes. Still, due to the sharing of five genes between the B chromosomes of Psalidodon already analyzed, it can be supposed that the BfMa variant also shares a common origin with the other variants of the genus, in a process that occurred about 4 million years ago and that its origin was not due to recent interspecific hybridization. RT-qPCR analyzes in P. paranae gonads showed differential expression of three genes in females (cyp19a1a, esr1 and nobox), and two in males (dmrt1 and nobox). The under expression of the cyp19a1a and esr1 genes in females could reflect a dysregulation process caused by the B chromosome, or a response of the A genome to neutralize the B genome, or even a possible functional effect of these chromosomes, which would lead to a distortion of the reproductive period. The overexpression of the nobox gene could reflect the existence of a mechanism of accumulation involving these chromosomes, determining greater efficiency in the oogenesis process and greater reproductive success for +B females. In males, overexpression of the dmrt1 gene could cause an alteration in the reproductive cycle, as has already been observed before in P. scabripinnis.
B chromosomes are supernumerary elements found in the genome of eukaryotes and have several aspects still unknown. Despite its poor composition in protein-coding genes, the description of transcripts from these elements has changed the view that they are inert structures in the genome. Among the fish of the genus Psalidodon, a great diversity of these elements can be observed, with the occurrence of micro to macro B chromosomes, with different morphologies. Previous studies have demonstrated the occurrence of at least 21 genes in the B chromosomes of Psalidodon paranae and Psalidodon scabripinnis, with both species having a greater presence of B chromosomes in females, which suggests their role in sex differentiation pathways. Thus, the present study aimed to investigate the gene content of the BfMa variant of Psalidodon fasciatus to test the hypothesis of a common origin with other variants in the genus, as well as to investigate whether the presence of B chromosomes leads to the different expression of genes in the differentiation pathway of the sex in P. paranae. For this, individuals of P. paranae and P. fasciatus were collected and analyzed and the qPCR analysis allowed the identification of eight protein-coding genes in the BfMa variant of P. fasciatus (amhr2, ccpg1, cia30, g2e3, msh4, nobox, nusap1, and sbno2), being that six of these have already been described in the BfMb variant of the same species. Thus, it is highly likely that both variants have a common origin and have diversified to the point of losing or acquiring unique genes. Still, due to the sharing of five genes between the B chromosomes of Psalidodon already analyzed, it can be supposed that the BfMa variant also shares a common origin with the other variants of the genus, in a process that occurred about 4 million years ago and that its origin was not due to recent interspecific hybridization. RT-qPCR analyzes in P. paranae gonads showed differential expression of three genes in females (cyp19a1a, esr1 and nobox), and two in males (dmrt1 and nobox). The under expression of the cyp19a1a and esr1 genes in females could reflect a dysregulation process caused by the B chromosome, or a response of the A genome to neutralize the B genome, or even a possible functional effect of these chromosomes, which would lead to a distortion of the reproductive period. The overexpression of the nobox gene could reflect the existence of a mechanism of accumulation involving these chromosomes, determining greater efficiency in the oogenesis process and greater reproductive success for +B females. In males, overexpression of the dmrt1 gene could cause an alteration in the reproductive cycle, as has already been observed before in P. scabripinnis.
Descrição
Palavras-chave
Genômica, Citogenética, Astyanax, Cromossomos B, Genomics, Cytogenetics, B chromosome, Expressão gênica, Gene expression, Psalidodon