Mitogenômica da ordem Scleractinia (Cnidaria, Anthozoa): relações entre evolução da ordem e mudanças climáticas
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Data
2020-01-24
Autores
Seiblitz, Isabela Galvão de Lossio e [UNIFESP]
Orientadores
Kitahara, Marcelo Visentini [UNIFESP]
Tipo
Dissertação de mestrado
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Os corais escleractíneos, metazoários não bilatérios pertencentes ao filo Cnidaria, encontram-se ameaçados pelo aumento da temperatura e acidificação dos oceanos. Essas mudanças podem levar à morte ou saída de algas endossimbiontes (zooxantelas) dos corais, assim como à dissolução do esqueleto carbonático desses metazoários. A ordem Scleractinia, à qual esses organismos pertencem, não teve ainda sua história evolutiva totalmente resolvida. A filogenia de suas subordens e mesmo seu monofiletismo são incertos e essa dificuldade se deve, principalmente, ao baixo número de táxons incluídos nas filogenias, principalmente espécies de corais azooxantelados. Além disso, o escasso número de marcadores moleculares pode também levar a uma variação entre as topologias das diferentes reconstruções evolutivas da ordem. Desse modo, o presente estudo tem como objetivo principal recuperar a história evolutiva de Scleractinia com base em genomas mitocondriais de espécies de corais zooxantelados e azooxantelados, que foram analisadas por sequenciamento de última geração (NGS) nas plataformas NextSeq500 e MiSeq (Illumina). Durante a preparação de bibliotecas para sequenciamento, modificações no protocolo foram feitas e seus resultados indicam que: 1) a integridade do DNA parece ser relevante, mas dependendo do quão íntegro o DNA se encontra, pode-se utilizar os parâmetros de fragmentação do protocolo ou uma adaptação; 2) a diluição dos adaptadores não é essencial para prevenir a formação de dímeros dos mesmos, mas o número de ciclos na amplificação da biblioteca parece ser. Comparações de protocolos de enriquecimento de DNA mitocondrial indicaram o sucesso apenas de um dos protocolos testados, enquanto tentativas de separação de zooxantelas do tecido do coral não foram bem sucedidas. Um total de 62 genomas mitocondriais foi determinado/montado com sucesso e um foi obtido a partir de colaborações. Nesses, três padrões de rearranjo de genes foram encontrados, dois deles até então desconhecidos. Na reconstrução filogenética da ordem, a maior parte dos ramos apresenta suporte alto e a topologia parece, de modo geral, similar à recuperada em outros estudos. Algumas das diferenças observadas parecem ser suportadas com base em características morfológicas ou geográficas e outras indicam que alguns grupos precisam ser estudados de modo mais aprofundado. Dentre os passos futuros na execução deste estudo, fatores paleoclimáticos serão mapeados nessas reconstruções a partir de uma calibração por meio de relógio molecular. Com isso, será possível identificar o momento no qual certas características surgiram ou desapareceram, o que auxiliará na elaboração de hipóteses a respeito do futuro desses organismos frente às mudanças climáticas
Scleractinian corals, nonbilaterian Metazoa belonging to phylum Cnidaria, are currently threatened by global warming and ocean acidification. These changes may lead to either death or release of symbiotic algae (zooxanthellae) from corals, as well as to skeleton dissolution in these metazoans. The order Scleractinia, to which these organisms belong, has not had its evolutionary history completely resolved yet. The phylogeny of its suborders and even its monophyly are uncertain and the main reason for this difficulty is the low number of taxa included in phylogenies, especially in regard to azooxanthellate corals. Moreover, the low number of molecular markers used may also lead to a variation among topologies of different reconstructions of this order. For this purpose, this study aimed to recover the evolutionary history of Scleractinia based on mitochondrial genomes of 50 species of azooxanthellate and 50 of zooxanthellate corals, which are currently being analysed by next generation sequencing (NGS) on NextSeq500 and MiSeq platforms (Illumina). During library preparation for sequencing, protocol modifications were tested and their results indicate that: 1) DNA integrity seems to be relevant, but depending on how degraded the DNA is, it is possible to either use the default shearing parameters provided on the protocol or use an adaptation; and 2) dilution of adapters does not seem to be essential to prevent adapter dimer formation, but the number of cycles for library amplification seems to be. Among compared mitochondrial DNA enrichment protocols, only one seems to be successful while none of the attempts to dissociate Symbiodiniaceae from coral tissue succeeded. In total, 62 mitogenomes were assembled and one was obtained through collaboration. Three patterns of gene rearrangement were found, two of which were described for the first time. In a phylogenetic reconstruction of Scleractinia, the majority of branches were highly supported and broad tree topology was similar to previous studies. Some of the observed differences seem to be supported based on morphological or geographic traits while other divergences indicate that some groups need to be studied in a more comprehensive way. Regarding future steps for this study, palaeoclimate factors will be mapped to these reconstructions based on a molecular clock calibration. Therefore, it will be possible to identify when specific features appeared and disappeared, supporting the elaboration of hypotheses regarding the future of scleractinian corals towards climate change
Scleractinian corals, nonbilaterian Metazoa belonging to phylum Cnidaria, are currently threatened by global warming and ocean acidification. These changes may lead to either death or release of symbiotic algae (zooxanthellae) from corals, as well as to skeleton dissolution in these metazoans. The order Scleractinia, to which these organisms belong, has not had its evolutionary history completely resolved yet. The phylogeny of its suborders and even its monophyly are uncertain and the main reason for this difficulty is the low number of taxa included in phylogenies, especially in regard to azooxanthellate corals. Moreover, the low number of molecular markers used may also lead to a variation among topologies of different reconstructions of this order. For this purpose, this study aimed to recover the evolutionary history of Scleractinia based on mitochondrial genomes of 50 species of azooxanthellate and 50 of zooxanthellate corals, which are currently being analysed by next generation sequencing (NGS) on NextSeq500 and MiSeq platforms (Illumina). During library preparation for sequencing, protocol modifications were tested and their results indicate that: 1) DNA integrity seems to be relevant, but depending on how degraded the DNA is, it is possible to either use the default shearing parameters provided on the protocol or use an adaptation; and 2) dilution of adapters does not seem to be essential to prevent adapter dimer formation, but the number of cycles for library amplification seems to be. Among compared mitochondrial DNA enrichment protocols, only one seems to be successful while none of the attempts to dissociate Symbiodiniaceae from coral tissue succeeded. In total, 62 mitogenomes were assembled and one was obtained through collaboration. Three patterns of gene rearrangement were found, two of which were described for the first time. In a phylogenetic reconstruction of Scleractinia, the majority of branches were highly supported and broad tree topology was similar to previous studies. Some of the observed differences seem to be supported based on morphological or geographic traits while other divergences indicate that some groups need to be studied in a more comprehensive way. Regarding future steps for this study, palaeoclimate factors will be mapped to these reconstructions based on a molecular clock calibration. Therefore, it will be possible to identify when specific features appeared and disappeared, supporting the elaboration of hypotheses regarding the future of scleractinian corals towards climate change
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Citação
SEIBLITZ, Isabela Galvão de Lossio e. Mitogenômica da ordem Scleractinia (Cnidaria, Anthozoa): relações entre evolução da ordem e mudanças climáticas. 2020. 99 f. Dissertação (Mestrado em Biodiversidade e Ecologia Marinha e Costeira) - Instituto do Mar, Universidade Federal de São Paulo, Santos, 2020