RESUMO
Biogeographic and evolutionary patterns in the North African portion of the Western Palaearctic are poorly known. A high fraction of undescribed diversity is expected in this region, especially in groups such as reptiles. Here we used mitochondrial (12S, 16S, cytb) and nuclear (pomc, rag2, cmos) markers and morphological data to investigate phyletic diversification and phylogeographical structure in the amphisbaenian Trogonophis wiegmanni endemic to the Maghreb. Phylogenetic and molecular dating analyses based on gene trees and species trees support three deeply divergent lineages of Pliocene origin, two in Morocco and one in central Algeria and Tunisia. Parapatry, reciprocal monophyly, high genetic divergence and limited morphological differentiation between them suggest that these lineages represent independent cryptic taxonomic units. Emerging lines of evidence from this study and from available literature on Maghreb taxa support (i) a major biogeographic break between western and eastern Maghreb and (ii) a role of the Atlas as a biogeographic divide within the western Maghreb (Morocco). The origin of these biogeographic units is probably associated with the evolutionary events prompted by the Late Miocene palaeogeographic setting and later by Plio-Pleistocene climatic changes and their interplay with prominent orographic barriers within North Africa.
Assuntos
Lagartos/classificação , África do Norte , Proteínas de Anfíbios/classificação , Proteínas de Anfíbios/genética , Proteínas de Anfíbios/metabolismo , Animais , Biodiversidade , Evolução Biológica , DNA Mitocondrial/química , DNA Mitocondrial/classificação , DNA Mitocondrial/genética , Proteínas de Ligação a DNA/classificação , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Lagartos/genética , Marrocos , Filogenia , Filogeografia , Pró-Opiomelanocortina/classificação , Pró-Opiomelanocortina/genética , Pró-Opiomelanocortina/metabolismo , RNA Ribossômico/química , RNA Ribossômico/classificação , RNA Ribossômico/genéticaRESUMO
The presence and role of the pro-opiomelanocortin (POMC) gene and encoded peptides in invertebrates are here summarized and discussed. Some of the POMC-derived peptides show a significant similarity regarding their functions, suggesting their appearance before the split of protostomian-deuterostomian lineages and their maintenance during evolution. The basic mechanisms that govern the exchange of information between cells are usually well conserved, and this could have also been for POMC-derived peptides, that are mainly involved in fundamental functions such as immune and neuroendocrine responses. However, the presence and functions that POMC-derived peptides exhibit in taxonomically distant models, are not always reflected by the expected gene homology, leaving the problem of POMC evolution in invertebrates in need of additional study.
Assuntos
Evolução Biológica , Invertebrados/genética , Pró-Opiomelanocortina/genética , Animais , Humanos , Neuropeptídeos/genética , Neuropeptídeos/metabolismo , Filogenia , Pró-Opiomelanocortina/classificação , Pró-Opiomelanocortina/metabolismo , Estresse FisiológicoRESUMO
Proopiomelanocortin (POMC) plays an essential role in the stress response of the hypothalamic-pituitary-adrenal axis, and is the precursor of biologically active peptides such as adrenocorticotropin (ACTH), alpha-melanocyte-stimulating hormone (alpha-MSH), beta-melanocyte-stimulation hormone (beta-MSH) and beta-endorphin. We have synthesized two different forms of POMC cDNA clones, POMC-I and POMC-II, from a pituitary cDNA library for Paralichthys olivaceus, or Japanese flounder. jfPOMC-I cDNA consists of 954bp and encodes a polypeptide of 216 amino acid residues, whereas jfPOMC-II consists of 971bp which encode a polypeptide of 194 amino acid residues. The high levels of jfPOMC-I and -II mRNAs detected in the pituitary tissue and moderate levels detected in the brain tissue plus our quantitative RT-PCR analysis, which showed there to be no significant difference between the levels of jfPOMC-I and -II mRNAs, indicate that there may be no functional separation between these two mRNAs in the flounder.
Assuntos
Pró-Opiomelanocortina/genética , Pró-Opiomelanocortina/metabolismo , RNA Mensageiro/genética , Sequência de Aminoácidos , Animais , Encéfalo/metabolismo , Clonagem Molecular , DNA Complementar/genética , Linguado , Dados de Sequência Molecular , Filogenia , Hipófise/metabolismo , Pró-Opiomelanocortina/química , Pró-Opiomelanocortina/classificação , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Homologia de Sequência de AminoácidosRESUMO
Characterization of a newly cloned proopiomelanocortin (POMC) gene in the teleost zebrafish, Danio rerio, is reported. This gene is formed by three exons and two introns, and its complete cDNA codes for a polypeptide of 222 amino acids. Zebrafish proopiomelanocortin (zfPOMC) contains the consensus sequences for ACTH, gamma-LPH, beta-MSH and beta-endorphin (beta-END). RT-PCR expression studies indicate that zfPOMC is selectively expressed in nervous tissue and in the pituitary gland. An homologous sequence to zfPOMC in the zebrafish genome is also presented. It is possible that this sequence represents part of a duplicate POMC, which might have appeared as a result of an extra genome duplication that have taken place in the cyprinidae family or even in all teleosts. Comparisons between the two zebrafish beta-endorphins and among these peptides and its homologues in other species are also presented.