RESUMO
Mitochondrial adrenodoxins (ADXs) are small iron-sulfur proteins with electron transfer properties. In animals, ADXs transfer electrons between an adrenodoxin reductase (ADXR) and mitochondrial P450s, which is crucial for steroidogenesis. Here we show that a plant mitochondrial steroidogenic pathway, dependent on an ADXR-ADX-P450 shuttle, is essential for female gametogenesis and early embryogenesis through a maternal effect. The steroid profile of maternal and gametophytic tissues of wild-type (WT) and adxr ovules revealed that homocastasterone is the main steroid present in WT gametophytes and that its levels are reduced in the mutant ovules. The application of exogenous homocastasterone partially rescued adxr and P450 mutant phenotypes, indicating that gametophytic homocastasterone biosynthesis is affected in the mutants and that a deficiency of this hormone causes the phenotypic alterations observed. These findings also suggest not only a remarkable similarity between steroid biosynthetic pathways in plants and animals but also a common function during sexual reproduction.
Assuntos
Adrenodoxina/metabolismo , Arabidopsis/embriologia , Ferredoxina-NADP Redutase/metabolismo , Sequência de Aminoácidos , Arabidopsis/genética , Sistema Enzimático do Citocromo P-450/metabolismo , Sistema Enzimático do Citocromo P-450/fisiologia , Transporte de Elétrons , Complexo de Proteínas da Cadeia de Transporte de Elétrons/metabolismo , Complexo de Proteínas da Cadeia de Transporte de Elétrons/fisiologia , Desenvolvimento Embrionário/genética , Gametogênese/fisiologia , Células Germinativas Vegetais/metabolismo , Mitocôndrias/metabolismo , Membranas Mitocondriais/metabolismo , Fitosteróis/biossíntese , Ligação ProteicaRESUMO
Steroid hormones are essential for the biological processes of eukaryotic organisms. The steroid endocrine system of C. elegans, which includes dafachronic acids (DA) and the nuclear receptor ceDAF-12, provides a simple model for exploring the role of steroid hormone signaling pathways in animals. In this study, we show for the first time the feasibility of designing synthetic steroids that can modulate different physiological processes, such as development, reproduction and ageing, in relation to ceDAF-12. Our results not only confirm the conclusions derived from genetic studies linking these processes but also provide new chemical tools to selectively manipulate them, as we found that different compounds produce different phenotypic results. The structures of these compounds are much more diverse than those of endogenous hormones and analogues previously described by other researchers, allowing further development of the chemical modulation of the steroid endocrine system in C. elegans and related nematodes.