A mitochondria-targeted antioxidant and a thyroid hormone interact to influence carotenoid-based bill coloration of zebra finches
32 Conspicuous ornaments in animals can evolve to reveal individual quality when their 33 production/maintenance costs make them reliable as signals or if their expression level is 34 intrinsically linked to quality by some unfalsifiable mechanism (quality indices). The 35 latter has been mostly ass...
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| Tipo de documento: | dissertação |
| Estado: | Versión enviada para evaluación y publicación |
| Data de publicação: | 2018 |
| País: | España |
| Recursos: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repositório: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:dnet:digitalcsic_::1457a124406f2f391fba7c86e6ca2bf6 |
| Acesso em linha: | http://hdl.handle.net/10261/426689 |
| Access Level: | Acceso aberto |
| Palavra-chave: | Cell metabolism Electron transport chain Mito-targeted antioxidants Oxidative stress Red colourations Sexual selection Sexual signalling Taeniopygia guttata |
| Resumo: | 32 Conspicuous ornaments in animals can evolve to reveal individual quality when their 33 production/maintenance costs make them reliable as signals or if their expression level is 34 intrinsically linked to quality by some unfalsifiable mechanism (quality indices). The 35 latter has been mostly associated with traits constrained by body size. However, red 36 ketocarotenoid-based coloured ornaments may also have evolved as quality indices 37 because their production could be closely linked to individual metabolism and, 38 particularly, to the cell respiration at the inner mitochondrial membrane (IMM). This 39 mechanism would supposedly not depend on resource (yellow carotenoids) availability, 40 thus discarding allocation trade-offs. A gene coding for a ketolase enzyme (CYP2J19) 41 responsible for converting dietary yellow carotenoids to red ketocarotenoids has recently 42 been described in birds. It is not known, however, if this ketolase is involved in 43 mitochondrial metabolism and if its expression level and activity is resource independent. 44 Here, we manipulated the metabolism of captive male zebra finches by an antioxidant 45 designed to penetrate the IMM (mitoTEMPO) and a thyroid hormone (triiodothyronine; 46 T3) with known hypermetabolic effects. The expression levels of a ketocarotenoid-based 47 ornament (bill redness) and CYP2J19 were measured. MitoTEMPO downregulated 48 CYP2J19 expression, supporting the mitochondrial involvement in ketolase function. T3 49 also reduced CYP2J19 expression, but at an intermediate dosage, this effect being 50 buffered by mitoTEMPO. Bill redness seemed to show a similar interacting effect. 51 Nevertheless, this faded when CYP2J19 expression level was controlled for as a 52 covariate. We argue that the well-known mitoTEMPO effect in reducing mitochondrial 53 reactive oxygen species (ROS) production (particularly superoxide) could have interfered 54 on redox signalling mechanisms controlling ketolase transcription. High T3 levels, 55 contrarily, can lead to high ROS production but also trigger compensatory mechanisms, 56 which may explain the U-shaped effect with dosage on CYP2J19 expression 56 levels. Bill 57 CYP2J19 expression values were also positively correlated to redness and circulating 58 substrate carotenoid levels. Nonetheless, treatment effects did not change when 59 controlling for blood carotenoid concentration, suggesting that resource-availability 60 dependence was irrelevant. Finally, our findings reveal a role for thyroid hormones in the 61 expression of carotenoid-based ornaments that has virtually been ignored until now. |
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