RESUMEN
The enzymatic-silicatein mediated formation of the skeletal elements, the spicules of siliceous sponges starts intracellularly and is completed extracellularly. With Suberites domuncula we show that the axial growth of the spicules proceeds in three phases: (I) formation of an axial canal; (II) evagination of a cell process into the axial canal, and (III) assembly of the axial filament composed of silicatein. During these phases the core part of the spicule is synthesized. Silicatein and its substrate silicate are stored in silicasomes, found both inside and outside of the cellular extension within the axial canal, as well as all around the spicule. The membranes of the silicasomes are interspersed by pores of ≈ 2 nm that are likely associated with aquaporin channels which are implicated in the hardening of the initial bio-silica products formed by silicatein. We can summarize the sequence of events that govern spicule formation as follows: differential GENETIC READOUT (of silicatein) â FRACTAL ASSOCIATION of the silicateins â EVAGINATION of cells by hydro-mechanical forces into the axial canal â and finally PROCESSIVE BIO-SILICA POLYCONDENSATION around the axial canal. We termed this process, occurring sequentially or in parallel, BIO-INORGANIC SELF-ORGANIZATION.
Asunto(s)
Catepsinas/metabolismo , Silicatos/metabolismo , Dióxido de Silicio/metabolismo , Suberites/metabolismo , Animales , Gránulos Citoplasmáticos/metabolismo , Gránulos Citoplasmáticos/ultraestructura , Vesículas Citoplasmáticas/metabolismo , Vesículas Citoplasmáticas/ultraestructura , Inmunohistoquímica , Microscopía Electrónica de Transmisión , Modelos Biológicos , Espectrometría por Rayos X , Suberites/citología , Suberites/ultraestructuraRESUMEN
The metabolic energy state of sponge tissue in vivo is largely unknown. Quantitative bioluminescence-based imaging was used to analyze the ATP distribution of Suberites domuncula (Olivi 1792) tissue, in relation to differences between the cortex and the medulla. This method provides a quantitative picture of the ATP distribution closely reflecting the in vivo situation. The obtained data suggest that the highest ATP content occurs around channels in the sponge medulla. HPLC reverse-phase C-18, used for measurement of ATP content, established a value of 1.62 µmol ATP g⻹ dry mass in sponge medulla, as opposed to 0.04 µmol ATP g⻹ dry mass in the cortex, thus indicating a specific and defined energy distribution. These results correlate with the mitochondria localization, determined using primary antibodies against cytochrome oxidase c subunit 1 (COX1) (immunostaining), as well as with the distribution of arginine kinase (AK), essential for cellular energy metabolism (in situ hybridization with AK from S. domuncula; SDAK), in sponge sections. The highest energy consumption seemed to occur in choanocytes, the cells that drive the water through the channel system of the sponge body. Taken together, these results showed that the majority of energetic metabolism in S. domuncula occurs in the medulla, in the proximity of aqueous channels.
Asunto(s)
Adenosina Trifosfato/metabolismo , Metabolismo Energético/fisiología , Mitocondrias/fisiología , Especificidad de Órganos/fisiología , Suberites/citología , Animales , Arginina Quinasa/metabolismo , Cromatografía Líquida de Alta Presión , Procesamiento de Imagen Asistido por Computador , Inmunohistoquímica , Hibridación in Situ , Suberites/metabolismoRESUMEN
Biosilicification in sponges is initiated by formation of proteinaceous filaments, predominantly consisting of silicateins. Silicateins enzymatically catalyze condensation of silica nanospheres, resulting in symmetric skeletal elements (spicules). In order to create tailored biosilica structures in biomimetic approaches it is mandatory to elucidate proteins that are fundamental for the assembly of filaments. Silintaphin-1 is a core component of modularized filaments and also part of a spicule-enfolding layer. It bears no resemblance to other proteins, except for the presence of an interaction domain that is fundamental for its function as scaffold/template. In the presence of silicatein silintaphin-1 facilitates the formation of in vitro filaments. Also, it directs the assembly of gamma-Fe(2)O(3) nanoparticles and surface-immobilized silicatein to rod-like biocomposites, synthetic spicules. Thus, silintaphin-1 will contribute to biomimetic approaches that pursue a controlled formation of patterned biosilica-based materials. Its combination with gamma-Fe(2)O(3) nanoparticles and immobilized silicatein will furthermore inspire future biomedical applications and clinical diagnostics.
Asunto(s)
Materiales Biomiméticos/metabolismo , Calcificación Fisiológica , Catepsinas/metabolismo , Proteínas/metabolismo , Suberites/enzimología , Secuencia de Aminoácidos , Animales , Anticuerpos/farmacología , Calcificación Fisiológica/efectos de los fármacos , Catepsinas/ultraestructura , ADN Complementario/genética , Enzimas Inmovilizadas/metabolismo , Compuestos Férricos/metabolismo , Datos de Secuencia Molecular , Unión Proteica/efectos de los fármacos , Transporte de Proteínas/efectos de los fármacos , Proteínas/química , Proteínas Recombinantes/metabolismo , Regeneración/efectos de los fármacos , Ácido Silícico/farmacología , Suberites/anatomía & histología , Suberites/citología , Suberites/efectos de los fármacos , Técnicas del Sistema de Dos HíbridosRESUMEN
Sponges (phylum Porifera) are simple metazoans for which no molecular information on gametogenesis and larval development is available. To support the current study, it was confirmed by histology that oocytes and larvae were produced by the demosponge Suberites domuncula. Three genes/expressed products from S. domuncula whose expression correlated with sexual reproduction were identified and characterized (they are used here as marker genes): i) a receptor tyrosine kinase (RTK) with sequence similarity in the tyrosine kinase domain to fibroblast growth factor receptors; ii) the sex-determining protein FEM1 and iii) the sperm associated antigen (SAA) of triploblasts. Antibodies against the extracellular domain of the RTK specifically stained oocytes and larvae in S. domuncula tissue sections. Induction of these three genes was successful at elevated temperature, a factor which also promotes natural gametogenesis. In situ hybridization analyses revealed that FEM1 and SAA were expressed in those areas in which gametogenesis begins. Our results indicate that genes which play a role in sex determination may be present in Porifera.
Asunto(s)
Suberites/citología , Secuencia de Aminoácidos , Animales , Antígenos/genética , Secuencia de Bases , Biomarcadores/metabolismo , Diferenciación Celular , ADN/genética , Femenino , Regulación del Desarrollo de la Expresión Génica , Masculino , Datos de Secuencia Molecular , Oocitos/citología , Oocitos/metabolismo , Filogenia , Proteínas Tirosina Quinasas Receptoras/genética , Proteínas Tirosina Quinasas Receptoras/metabolismo , Estaciones del Año , Homología de Secuencia de Aminoácido , Procesos de Determinación del Sexo , Espermatozoides/inmunología , Espermatozoides/metabolismo , Suberites/genética , Suberites/metabolismoRESUMEN
Sponges (phylum Porifera) represent the oldest metazoans. Their characteristic metazoan adhesion molecules and transcription factors enable them to establish a complex "Bauplan"; three major differentiated cell types (epithelial cells, skeletal cells/sclerocytes, and contractile cells) can be distinguished. Since no molecular markers are as yet available to distinguish these somatic cells or the corresponding embryonic cells from which they originate, we have selected the following three genes for their characterization: noggin (a signaling molecule in development), a caspase that encodes an apoptotic molecule, and silicatein. Silicatein is an enzyme that is involved in the synthesis of siliceous spicules and can hence be considered as a marker for scleroblasts. We have used the demosponge Suberites domuncula as a model system. During the hatching of the gemmules (asexual reproduction bodies) of S. domuncula, the expression of both noggin and caspase increases, whereas no transcripts for silicatein can be detected, irrespective of the presence of silicate or ferric iron (Fe3+) in the medium. In contrast, in adult specimens, silicate/Fe3+ cause an increased expression of these genes. In situ analysis has revealed that the first cells that express noggin, caspase, and silicatein lie in the epithelial layer of the pinacoderm. In a later phase, the noggin- and silicatein-positive cells migrate into the mesohyl, where they are found in association with spicules. Thus, the pinacoderm of sponges contains cells that have a differentiating capacity and from which somatic cells, such as skeletal cells/sclerocytes, derive.