Aspects of gene regulation in the diploid and tetraploid Odontophrynus americanus (Amphibia, Anura, Leptodactylidae)

Abstract

Erythropoietic and hemoglobin DNA transcriptional activities were analyzed in the diploid and the tetraploid Odontophrynus americanus. Flow cytometric analyses of DNA, RNA and mitochondrial contents showed increased genic activity in both diploid and tetraploid animals during erythropoiesis in vivo elicited by pretreatment phenylhydrazine. Generally, higher values were seen in immature tetraploid erythroid cells. On the 10th day of recovery from anemia, large amounts of messenger RNA were found in both specimens. Based on the mitochondrial content, the tetraploid cells had more intense energy metabolism than the diploid cells. Diploid O. americanus had about three times more erythroid cells than tetraploid specimens, indicating that there were differences in the regulatory mechanisms of erythroid cells. Hematological parameters showed that tetraploid cells had 30% more hemoglobin than the diploid, suggesting a regulatory mechanism of hemoglobin synthesis at the transcriptional level. Cytoplasmic inclusions resembling Heinz bodies were found in both types of cells. In the tetraploid cells they were previously found associated with RNA or RNP, suggesting that other regulatory system which controls the accumulation of nontranslated RNA transcribed in excess must be present. These differences at the physiological and molecular levels during erythropoiesis reinforce the hypothesis that speciation is occurring between diploid and tetraploid O. americanus.<br>A eritropoese e a atividade de transcrição de DNA de hemoglobina foram analisadas em Odontophrynus americanus diplóides e tetraplóides. Dados de conteúdo celular relativo de DNA, RNA e mitocôndrias obtidos por citometria de fluxo mostraram uma atividade gênica aumentada em ambos os animais durante a eritropoese in vivo estimulada por tratamento com fenilhidrazina, com valores maiores em eritrócitos tetraplóides imaturos. No décimo dia de recuperação da anemia foram encontradas grandes quantidades de RNA mensageiro em ambos espécimens. Com base no conteúdo mitocondrial, as células tetraplóides apresentaram um metabolismo energético mais intenso. O. americanus diplóides apresentaram três vezes mais células eritróides que os animais tetraplóides, caracterizando um mecanismo regulador da produção de células eritróides. Determinações hematológicas mostraram que as células tetraplóides contêm 30% mais hemoglobina que as células diplóides. Uma vez que 25-30% mais ribossomos estão presentes nas células tetraplóides, parece que um mecanismo regulador da síntese de hemoglobina esteja relacionado ao nível transcricional. Como as inclusões citoplasmáticas semelhantes a corpos de Heinz, porém associadas com RNA ou RNP, são encontradas em ambos os espécimens, é possível que outro mecanismo regulador esteja presente, similar ao das "hidden breaks" descritas em peixes poliplóides, acumulando rRNA transcrito em excesso e não traduzido. Estas diferenças em níveis fisiológicos e moleculares, detectadas durante a eritropoese, reforçam que divergências em nível de especiação estão em c...

Speciation Routes of Anurans

“…Duplication of genes allows that although variability of the species is maintained by two genes of each allele, the two remaining homologous genes are free to mutate and eventually be positively selected leading to advantageous diversification and expansion of niches occupied by the tetraploid species [16]. These results are coherent with the concept of evolution by gene duplication [17]; (3) that there is a lower hemoglobin content in the 4n as to the 2n animals [18]; (4) that the reduced gene expression in the 4n animals is caused by the repression of half of the rDNA cistrons [19]; (5) that there is an amphiplasty configuration characterized by diphasic stages of cell cycle revealed in the two halves of the 4n genome. It may point differences in the DNA replication time probably caused by methylation [4,20].…”

Review Polyploidy and epigenetic events in the evolution of Anura

“…This hypothesis was further supported by data on erythropoiesis and on the transcription of DNA coding for hemoglobin in 2n and 4n O. americanus, which revealed that the 4n cells have only 30% more hemoglobin and 25-30% more ribosomes than do 2n cells (Cianciarullo et al, 2000).…”

Proliferation following tetraploidization regulates the size and number of erythrocytes in the blood flow during medaka development, as revealed by the abnormal karyotype of erythrocytes in the medaka TFDP1 mutant

“…The size of erythrocytes increases when polyploidy occurs, with the advantage of an increased content of hemoglobin (Cianciarullo et al, 2000), supporting the possibility that medaka embryos having 4N erythrocytes maybe more resistant to hypoxia. Furthermore, we analyzed the relationship between the blood flow and erythropoiesis in medaka embryonic development, and investigated the proliferation of 4N erythrocytes in the blood flow.…”

“…In mice, there are 2 reports indicating the proliferation of erythrocytes in the blood flow in E11 embryos labeled with thymidine (De La Chapelle et al, 1969) or examined by cell-cycle analysis (Sangiorgi et al, 1990) with no further investigation. Our observations reveal the size regulation of erythrocytes in the phase transition of blood flow by cell cycle regulation in embryonic development.The size of erythrocytes increases when polyploidy occurs, with the advantage of an increased content of hemoglobin (Cianciarullo et al, 2000), supporting the possibility that medaka embryos having 4N erythrocytes maybe more resistant to hypoxia. Furthermore, we analyzed the relationship between the blood flow and erythropoiesis in medaka embryonic development, and investigated the proliferation of 4N erythrocytes in the blood flow.…”