PublicaĆ§Ć£o
Unravelling mixotrophy in dinoflagellates: connecting transcript analysis to physiological rate measurements across light intensities
| datacite.subject.fos | CiĆŖncias Naturais | |
| dc.contributor.advisor | Ferreira, Guilherme Duarte | |
| dc.contributor.advisor | FelĆcio, VerĆ³nica Manuela RĆ“xo | |
| dc.contributor.author | Almeida, Mafalda de Carvalho | |
| dc.date.accessioned | 2026-06-08T10:15:47Z | |
| dc.date.available | 2026-06-08T10:15:47Z | |
| dc.date.issued | 2026-05-12 | |
| dc.description.abstract | Mixotrophy, the fusion between photosynthesis and phagotrophy within a single cell, is a dominant nutritional strategy in marine plankton, conferring a significant competitive advantage in variable environments. However, the molecular mechanisms regulating the balance between these two metabolic pathways remain poorly understood. This dissertation investigated the physiological and molecular regulation of the dinoflagellate Karlodinium veneficum under three different light regimes of 7, 45, and 300 PAR.mā»Ā².sā»Ā¹ under contrasting trophic strategies, by comparing autotrophy against mixotrophy utilizing Rhodomonas salina as prey. Through an integrative approach, physiological rates (growth, ingestion, respiration, photosynthesis) were quantified, cellular energy allocation (lipids, carbohydrates, ATP) and the expression of key metabolic genes were analysed. The results revealed that a light intensity of 45 Ī¼mol PAR.mā»Ā².sā»Ā¹ represents the metabolic optimum for mixotrophy, maximizing ingestion rates and photosynthetic efficiency. Unexpectedly, autotrophic growth exceeded mixotrophic growth, suggesting energetic costs associated with predation. Nevertheless, mixotrophic cells demonstrated a higher capacity for energy reserve accumulation and superior photosynthetic rates, indicating a metabolic synergy where prey ingestion enhances the photosynthetic machinery. Connecting transcript analysis to physiological rates, the molecular data provided a mechanistic explanation for the observed metabolic strategy. The transcriptional stability of phosphoribulokinase, prk, underpinned the sustained photosynthetic rates and ATP production observed across trophic modes, confirming that the Calvin cycle operates constitutively and is not repressed by feeding. Simultaneously, the apparent downregulation of cytochrome c oxidase subunit I, cox1, under mixotrophy aligned with the physiological increase in gross oxygen production efficiency. This inverse relationship suggests that prey ingestion alleviates the respiratory burden of biosynthesis, allowing the cell to maximize photosynthetic output with reduced mitochondrial investment. This study highlights the complexity of mixotrophic regulation and underscores the importance of integrating molecular and physiological tools to understand the role of these organisms in marine ecosystem. | eng |
| dc.description.abstract | Mixotrofia, a fusĆ£o entre a fotossĆntese e a fagotrofia numa Ćŗnica cĆ©lula, Ć© uma estratĆ©gia nutricional dominante no plĆ¢ncton marinho, conferindo uma vantagem competitiva significativa em vĆ”rios ambientes. No entanto, os mecanismos moleculares que regulam o equilĆbrio entre estas duas vias metabĆ³licas permanecem pouco estudados. Esta dissertaĆ§Ć£o investigou a regulaĆ§Ć£o fisiolĆ³gica e molecular do dinoflagelado Karlodinium veneficum sob trĆŖs regimes de luz de 7, 45 e 300 PAR.mā»Ā².sā»Ā¹ em estratĆ©gias trĆ³ficas contrastantes, comparando a autotrofia com a mixotrofia utilizando Rhodomonas salina como presa. AtravĆ©s de uma abordagem integrativa, foram quantificadas as taxas fisiolĆ³gicas (crescimento, ingestĆ£o, respiraĆ§Ć£o, fotossĆntese) e analisadas a alocaĆ§Ć£o de energia celular (lĆpidos, hidratos de carbono, ATP) e a expressĆ£o de genes metabĆ³licos chave. Os resultados revelaram que uma intensidade luminosa de 45 PAR.mā»Ā².sā»Ā¹ representa os melhores resultados metabĆ³licos para a mixotrofia, maximizando as taxas de ingestĆ£o e a eficiĆŖncia fotossintĆ©tica. Todavia, o crescimento autotrĆ³fico foi superior ao crescimento mixotrĆ³fico, sugerindo custos energĆ©ticos associados Ć predaĆ§Ć£o. Por contraste, as cĆ©lulas mixotrĆ³ficas demonstraram uma maior capacidade de acumulaĆ§Ć£o de reservas energĆ©ticas e taxas fotossintĆ©ticas superiores, indicando uma sinergia metabĆ³lica onde a ingestĆ£o de presas potencia a maquinaria fotossintĆ©tica. Ao analisar a expressĆ£o genĆ©tica Ć luz dos dados fisiolĆ³gicos, surge uma explicaĆ§Ć£o interessante para a estratĆ©gia metabĆ³lica observada. A estabilidade transcricional da fosforibulocinase, prk, sustentou as taxas fotossintĆ©ticas e a produĆ§Ć£o de ATP mantidas entre os diferentes modos trĆ³ficos, confirmando que o ciclo de Calvin opera constitutivamente e que nĆ£o Ć© reprimido pela alimentaĆ§Ć£o. Simultaneamente, a aparente diminuiĆ§Ć£o da expressĆ£o da subunidade I do citocromo c oxidase, cox1, em organismos mixotrĆ³ficos alinhou-se com o aumento fisiolĆ³gico da eficiĆŖncia da produĆ§Ć£o bruta de oxigĆ©nio. Esta relaĆ§Ć£o inversa sugere que a ingestĆ£o de presas alivia a carga respiratĆ³ria da biossĆntese, permitindo Ć cĆ©lula maximizar o rendimento fotossintĆ©tico com um investimento mitocondrial reduzido. Este estudo destaca, portanto, a complexidade da regulaĆ§Ć£o mixotrĆ³fica e sublinha a importĆ¢ncia de integrar ferramentas moleculares e fisiolĆ³gicas para compreender o papel destes organismos no ecossistema marinho. | por |
| dc.identifier.tid | 204312752 | |
| dc.identifier.uri | http://hdl.handle.net/10400.8/16379 | |
| dc.language.iso | eng | |
| dc.rights.uri | N/A | |
| dc.subject | Mixotrophy | |
| dc.subject | Karlodinium veneficum | |
| dc.subject | Metabolism Regulation | |
| dc.subject | Abiotic Variations | |
| dc.subject | Physiology | |
| dc.subject | Differential Gene Expression | |
| dc.title | Unravelling mixotrophy in dinoflagellates: connecting transcript analysis to physiological rate measurements across light intensities | eng |
| dc.type | master thesis | |
| dspace.entity.type | Publication | |
| thesis.degree.name | Mestrado em Biotecnologia dos Recursos Marinhos |