Isoquercitrin and polyphosphate co-enhance mineralization of human osteoblast-like SaOS-2 cells via separate activation of two RUNX2 cofactors AFT6 and Ets1.

Isoquercitrin, a dietary phytoestrogen, is a potential stimulator of bone mineralization used for prophylaxis of osteoporotic disorders. Here we studied the combined effects of isoquercitrin, a cell membrane permeable 3-O-glucoside of quercetin, and polyphosphate [polyP], a naturally occurring inorganic polymer inducing bone formation, on mineralization of human osteoblast-like SaOS-2 cells. Both compounds isoquercitrin and polyP induce at non-toxic concentrations the mineralization process of SaOS-2 cells. Co-incubation experiments revealed that isoquercitrin (at 0.1 and 0.3µM), if given simultaneously with polyP (as Ca(2+) salt; at 3, 10, 30 and 100µM) amplifies the mineralization-enhancing effect of the inorganic polymer. The biomineralization process induced by isoquercitrin and polyP is based on two different modes of action. After incubation of the cells with isoquercitrin or polyP the expression of the Runt-related transcription factor 2 [RUNX2] is significantly upregulated. In addition, isoquercitrin causes a strong increase of the steady-state-levels of the two co-activators of RUNX2, the activating transcription factor 6 [ATF6] and the Ets oncogene homolog 1 [Ets1]. The activating effect of isoquercitrin occurs via a signal transduction pathway involving ATF6, and by that, is independent from the induction cascade initiated by polyP. This conclusion is supported by the finding that isoquercitrin upregulates the expression of the gene encoding for osteocalcin, while polyP strongly increases the expression of the Ets1 gene and of the alkaline phosphatase. We show that the two compounds, polyP and isoquercitrin, have a co-enhancing effect on bone mineral formation and in turn might be of potential therapeutic value for prevention/treatment of osteoporosis.

Flashing light signaling circuit in sponges: endogenous light generation after tissue ablation in Suberites domuncula.

The skeleton of siliceous sponges (phylum Porifera: classes Demospongiae and Hexactinellida), composed of tightly interacting spicules that assemble to a genetically fixed scaffold, is formed of bio-silica. This inorganic framework with the quality of quartz glass has been shown to operate as light waveguide in vitro and very likely has a similar function in vivo. Furthermore, the molecular toolkit for endogenous light generation (luciferase) and light/photon harvesting (cryptochrome) has been identified in the demosponge Suberites domuncula. These three components of a light signaling system, spicules-luciferase-cryptochrome, are concentrated in the surface layers (cortex) of the poriferan body. Specimens from which this cortex has been removed/ablated do not emit light. However, with regeneration and reconstitution of the cortex the animals re-gain the capacity to flash light. This newly discovered characteristic of sponges to generate light prompted us to investigate the genetic basis for the endogenous light signaling system. As a potential transcription factor involved in the expression of luciferase and cryptochrome, a SOX-related protein has been identified. In dark-adapted animals or in tissue from below the cortex region, the medulla, no gene or protein expression of SOX-related protein, luciferase, and cryptochrome could be detected. However, during the regeneration of the cortex, a stage-specific expression pattern was recorded: SOX-related protein > luciferase > cryptochrome. We conclude that a flashing light signaling circuit exists, which might control the retinoic acid-induced differentiation of stem cells into pulsating and contracting sponge cells, that is, pinacocytes and myocytes.

A cryptochrome-based photosensory system in the siliceous sponge Suberites domuncula (Demospongiae).

Based on the light-reactive behavior of siliceous sponges, their intriguing quartz glass-based spicular system and the existence of a light-generating luciferase [Müller WEG et al. (2009) Cell Mol Life Sci 66, 537-552], a protein potentially involved in light reception has been identified, cloned and recombinantly expressed from the demosponge Suberites domuncula. Its sequence displays two domains characteristic of cryptochrome, the N-terminal photolyase-related region and the C-terminal FAD-binding domain. The expression level of S. domuncula cryptochrome depends on animal's exposure to light and is highest in tissue regions rich in siliceous spicules; in the dark, no cryptochrome transcripts/translational products are seen. From the experimental data, it is proposed that sponges might employ a luciferase-like protein, the spicular system and a cryptochrome as the light source, optical waveguide and photosensor, respectively.

Isolation and characterization of a Mn(II)-oxidizing Bacillus strain from the demosponge Suberites domuncula.

In this study we demonstrate that the demosponge Suberites domuncula harbors a Mn(II)-oxidizing bacterium, a Bacillus strain, termed BAC-SubDo-03. Our studies showed that Mn(II) stimulates bacterial growth and induces sporulation. Moreover, we show that these bacteria immobilize manganese on their cell surface. Comparison of the 16S rDNA sequence allowed the grouping of BAC-SubDo-03 to the Mn-precipitating bacteria. Analysis of the spore cell wall revealed that it contains an Mn(II)-oxidizing enzyme. Co-incubation studies of BAC-SubDo-03 with 100 µM MnCl(2) and >1 µM of CuCl(2) showed an increase in their Mn(II)-oxidizing capacity. In order to prove that a multicopper oxidase-like enzyme(s) (MCO) exists in the cell wall of the S. domuncula-associated BAC-SubDo-03 Bacillus strain, the gene encoding this enzyme was cloned (mnxG-SubDo-03). Sequence alignment of the deduced MCO protein (MnxG-SubDo-03) revealed that the sponge bacterium clusters together with known Mn(II)-oxidizing bacteria. The expression of the mnxG-SubDo-03 gene is under strong control of extracellular Mn(II). Based on these findings, we assume that BAC-SubDo-03 might serve as a Mn reserve in the sponge providing the animal with the capacity to detoxify Mn in the environment. Applying the in vitro primmorph cell culture system we could demonstrate that sponge cells, that were co-incubated with BAC-SubDo-03 in the presence of Mn(II), show an increased proliferation potential.

Strombine dehydrogenase in the demosponge Suberites domuncula: characterization and kinetic properties of the enzyme crucial for anaerobic metabolism.

Previously, the cDNA and the respective gene for a presumed tauropine dehydrogenase (TaDH) from Suberites domuncula (GenBank accession nos. AM712888, AM712889) had been annotated. The conclusion that the sequences encode a TaDH had been inferred from the 68% identity with the TaDH protein from the marine demosponge Halichondria japonica. However, subsequent enzymatic assays shown here indicate that the presumed S. domuncula opine dehydrogenase is in fact a strombine dehydrogenase (StDH). The enzyme StDH is highly specific for glycine and is inhibited by an excess of the substrate pyruvate. Besides kinetic data, we report in this study also on the predicted tertiary and quaternary structure of the sponge StDH. It is concluded that the dimer (75 kDa) has a novel structure, distinguishing it from other known marine invertebrate OpDHs that exist as monomers.

Towards a molecular systematics of the Lake Baikal/Lake Tuva sponges.

Lake Baikal is famous for its extensive biodiversity that is equaled only by few other lakes. Fascinatingly, about 80% of all the animals the lake hosts are endemic. Sponges (Porifera) that live in symbiosis with photosynthetic algae are the most abundant animal taxon found in the littoral zone of Lake Baikal and have been grouped to the family Lubomirskiidae. In recent years, several attempts to determine the phylogenetic relationship between Lubomirskiidae and cosmopolitan freshwater sponges have been undertaken. Yet the results obtained remain inconclusive. Here, we strive to determine the phylogeny of freshwater sponges with the focus on endemic Lake Baikal species, also taking into account two poriferan species that were collected during an expedition in 2006 in two other isolated Siberian lakes, Lake Chagytai and Lake Tore-Khol. Since its discovery at the beginning of the twentieth century, the Lake Chagytai species was grouped to the Lubomirskiidae and called Baikalospongia dzhegatajensis. However, analyses of molecular sequence data [internal transcribed spacer 2 (ITS2), ribosomal DNA (rDNA)] and morphological markers (spicules, habitus) inferred a close relationship to the cosmopolitan genus Ephydatia and also to the Lake Tore-Khol species that had not so far been described. Thus, both species were tentatively termed Ephydatia tuva (Lake Chagytai) and E. altaiensis (Lake Tore-Khol). We hypothesize that these new species might have evolved from Ephydatia-like ancestors through adaptation to the unique environmental conditions of both lakes. To test the ITS data, an unlinked genetic locus was chosen for further phylogenetic analyses, the protein-coding gene silicatein. These analyses provided not only a more robust resolution between the Lubomirskiidae, but also corroborated the grouping of the Lake Chagytai and Lake Tore-Khol species to the genus Ephydatia. In addition, the phylogenetic analyses suggest a Spongilla-like founder generation of poriferan species in Lake Chagytai and Lake Tore-Khol. In conclusion, we propose that the process of speciation in Lake Baikal and Lake Chagytai/Lake Tore-Khol, from a cosmopolitan Spongilla-like ancestor to more than ten endemic species follows allopatric speciation patterns and is of the peripatric type.

Identification and isolation of a retrotransposon from the freshwater sponge Lubomirskia baicalensis: implication in rapid evolution of endemic sponges.

Transposons are mobile genetic elements that are found in all major branches of life. Similarities to retroviruses concerning genome structure and transposition mechanism suggest a familial relationship. Transposons are important evolutionary drivers that trigger genetic changes such as genomic rearrangement, alteration of gene expression, and gene duplication. And, indeed, now more than ever the effect of transposons on genome evolution represents a dynamic field of research. Since sponges (phylum Porifera) are the phylogenetically oldest still extant metazoan taxon, the study of poriferan mobile elements contributes to the understanding of the generation of phenotypic diversity and speciation at the base of the metazoan tree of life. This work describes the analyses of the first poriferan mobile genetic element so far identified, the long terminal repeats- retrotransposon Baikalum-1 of Lubomirskia baicalensis (Demospongiae; Ceractinomorpha). Baikalum-1 embraces a continuous open reading frame, putatively coding for a polyprotein that consists of nucleo capsid, protease, reverse transcriptase, RNase H, and integrase, all proteins/ enzymes characteristic of retrotransposons. Baikalum-1 was discovered in all freshwater sponge species endemic to Lake Baikal, as well as in cosmopolitan sponge species that inhabit a Lake Baikal-feeding rivulet. However, the same cosmopolitan species sampled from lakes and rivers (Siberian and European) with no direct contact to Lake Baikal did not contain this particular mobile genetic element. Thus, Baikalum-1 is probably the result of an evolutionarily ancient retroviral infection that spread exclusively amongst Baikalian sponge species. In addition, the retro-transposon is found in the vicinity of the silicatein-A1 gene. Silicateins are cathepsin-like proteins that catalyze the synthesis of poriferan siliceous skeletal elements (spicules). In L. baicalensis, the silicatein-A1 gene is flanked by two palindroms, probably remnants of transposons that might be responsible for the emergence of four different silicatein genes, uniquely present in freshwater but not marine sponges. Adaptation of sponges to the freshwater habitat (with its significantly higher silica content compared to the marine milieu) required the ability to evolve rapidly, which could be conferred by high transpositional activity, accompanied by duplication and diversification of the ancestral silicatein gene of marine species.

Silicateins, the major biosilica forming enzymes present in demosponges: protein analysis and phylogenetic relationship.

Silicateins are enzymes, which are restricted to sponges (phylum Porifera), that mediate the catalytic formation of biosilica from monomeric silicon compounds. The silicatein protein is compartmented in the sponges in the axial filaments which reside in the axial canals of the siliceous spicules. In the present study silicatein has been isolated from the freshwater sponge Lubomirskia baicalensis where it occurs in isoforms with sizes of 23 kDa, 24 kDa and 26 kDa. Since the larger protein is glycosylated we posit that it is a processed form of one of the smaller size forms. The silicatein isoforms are post-translationally modified by phosphorylation; at least four isoforms exist with pI's of 5.4, of 5.2, of 4.9 and of 4.7. Surprisingly silicatein not only mediates polymerization of silicate, but also displays proteolytic activity which is specific for cathepsin L enzymes, thus underscoring the high relationship of the silicateins to cathepsin L. The cDNAs from L. baicalensis for silicatein and cathepsin L, as well as the respective genes, were cloned. It was found that the five introns present in the sponge genes are highly conserved up to human cathepsin L. This analysis has been completed by sequencing of two silicatein genes (both for silicatein-alpha and -beta) and of cathepsin L from another demosponge, Suberites domuncula. A comprehensive phylogenetic analysis with these new sequences shed new light upon the evolution of cathepsin L and silicatein families which occurred at the base of the metazoan phyla. It is concluded, that in parallel with the emergence of these enzymes at first the number of introns increased, especially in the coding region of the mature enzyme. Later in evolution the number of introns decreased again. We postulate that modification of the catalytic triad, especially of its first amino acid, is a suitable target for a chemical modulation of enzyme function of the silicateins/cathepsin L.

Biosilica formation in spicules of the sponge Suberites domuncula: synchronous expression of a gene cluster.

The formation of spicules is a complicated morphogenetic process in sponges (phylum Porifera). The primmorph system was used to demonstrate that in the demosponge Suberites domuncula the synthesis of the siliceous spicules starts intracellularly and is dependent on the concentration of silicic acid. To understand spicule formation, a cluster of genes was isolated. In the center of this cluster is the silicatein gene, which codes for the enzyme that synthesizes spicules. This gene is flanked by an ankyrin repeat gene at one side and by a tumor necrosis factor receptor-associated factor and a protein kinase gene at the other side. All genes are strongly expressed in primmorphs and intact animals after exposure to silicic acid, and this expression is restricted to those areas where the spicule formation starts or where spicules are maintained in the animals. Our observations suggest that in S. domuncula a coordinated expression of physically linked genes is essential for the synthesis of the major skeletal elements.

Src proteins/src genes: from sponges to mammals.

The genome of marine sponge Suberites domuncula, a member of the most ancient and most simple metazoan phylum Porifera, encodes at least five genes for Src-type proteins, more than, i.e., Caenorhabditis elegans or Drosophila melanogaster (two in each). Three proteins, SRC1SD, SRC2SD and SRC3SD, were fully characterized. The overall homology (identity+similarity) among the three S. domuncula Srcs (68-71%) is much lower than the sequence conservation between orthologous Src proteins from freshwater sponges (82-85%). It is therefore very likely that several src genes/proteins were already present in the genome of Urmetazoa, the hypothetical metazoan ancestor. We have identified in the S. domuncula expressed sequence tags (ESTs) database further Src homology 2 (SH2) and 3 (SH3) domains that are unrelated to protein tyrosine kinases (PTKs). Src-related SH2 and SH3 domains from different species are much more conserved than SH2 and SH3 domains from different proteins in the same organism (S. domuncula), supporting the view that the common, ancestral src gene was already a multidomain protein composed of SH3, SH2 and tyrosine kinase (TK) domains. Two S. domuncula src genes were fully sequenced: src1SD gene has six and src2SD gene only one intron in front of SH2 domain, located at the same position in both genes. All vertebrate src genes, from fish to human, originated from the same ancestral gene, because they all have 10 introns at conserved positions. However, src genes in invertebrates have fewer introns that are located at different positions. Only the intron in front of the SH2 domain is present at the absolutely conserved position (and phase) in all known src genes, indicating that at least this intron was already present in the ancestral gene, common to all Metazoa. Our results also suggest that TK domain in this ancestral src was encoded on a single exon.

Oxygen-controlled bacterial growth in the sponge Suberites domuncula: toward a molecular understanding of the symbiotic relationships between sponge and bacteria.

Sponges (phylum Porifera), known to be the richest producers among the metazoans of bioactive secondary metabolites, are assumed to live in a symbiotic relationship with microorganisms, especially bacteria. Until now, the molecular basis of the mutual symbiosis, the exchange of metabolites for the benefit of the other partner, has not been understood. We show with the demosponge Suberites domuncula as a model that the sponge expresses under optimal aeration conditions the enzyme tyrosinase, which synthesizes diphenols from monophenolic compounds. The cDNA isolated was used as a probe to determine the steady-state level of gene expression. The gene expression level parallels the level of specific activity in sponge tissue, indicating that without aeration the tyrosinase level drops drastically; this effect is reversible. The SB2 bacterium isolated from the sponge surface grew well in M9 minimal salt medium supplemented with the dihydroxylated aromatic compound protocatechuate; this carbon source supported growth more than did glucose. From the SB2 bacterium the protocatechuate gene cluster was cloned and sequenced. This cluster comprises all genes coding for enzymes involved in the conversion of protocatechuate to acetyl coenzyme A. Expression is strongly induced if the bacteria are cultivated on M9-protocatechuate medium; the genes pcaQ (encoding the putative transcriptional activator of the pca operon) and pcaDC were used for quantitative PCR analyses. We conclude that metabolites, in this case diphenols, which might be produced by the sponge S. domuncula are utilized by the sponge surface-associated bacterium for energy generation. This rationale will help to further uncover the symbiotic pathways between sponges and their associated "nonculturable" microorganisms; our approach is flanked by the establishment of an EST (expressed sequence tags) database in our laboratory.

Sustainable production of bioactive compounds by sponges--cell culture and gene cluster approach: a review.

Sponges (phylum Porifera) are sessile marine filter feeders that have developed efficient defense mechanisms against foreign attackers such as viruses, bacteria, or eukaryotic organisms. Protected by a highly complex immune system, as well as by the capacity to produce efficient antiviral compounds (e.g., nucleoside analogues), antimicrobial compounds (e.g., polyketides), and cytostatic compounds (e.g., avarol), they have not become extinct during the last 600 million years. It can be assumed that during this long period of time, bacteria and microorganisms coevolved with sponges, and thus acquired a complex common metabolism. It is suggested that (at least) some of the bioactive secondary metabolites isolated from sponges are produced by functional enzyme clusters, which originated from the sponges and their associated microorganisms. As a consequence, both the host cells and the microorganisms lost the ability to grow independently from each other. Therefore, it was--until recently--impossible to culture sponge cells in vitro. Also the predominant number of "symbiotic bacteria" proved to be nonculturable. In order to exploit the bioactive potential of both the sponge and the "symbionts," a 3D-aggregate primmorph culture system was established; also it was proved that one bioactive compound, avarol/avarone, is produced by the sponge Dysidea avara. Another promising way to utilize the bioactive potential of the microorganisms is the cloning and heterologous expression of enzymes involved in secondary metabolism, such as the polyketide synthases.

Isolation and characterization of two T-box genes from sponges, the phylogenetically oldest metazoan taxon.

It is now well established that all metazoan phyla derived from one common ancestor, the hypothetical Urmetazoa. Due to the basal position of Porifera (Demospongiae) in the phylogenetic tree of Metazoa, studies on the mechanisms controlling the development of these animals can provide clues on the understanding of the origin of multicellular animals and on how the first organization of the body plan evolved. In this report we describe the isolation and genomic characterization of two T-box genes from the siliceous sponge Suberites domuncula. The phylogenetic analysis classifies one into the subfamily of Brachyury, Sd-Bra, and the second into the Tbx2 subfamily, Sd-Tbx2. Analyses of the Sd-Bra and Sd-Tbx2 sequences and their intron-exon structures demonstrate their basal position in the phylogeny of the T-box family, and allows us to hypothesize a model of the phylogenetic evolution of all T-box genes. Furthermore, we report the presence of two different products of alternative splicing of Sd-Bra, and demonstrate that they exist in different phosphorylation and glycosylation states in the sponge tissue. Sd-Bra expression in tissue and 3D-cell aggregates (primmorphs) is analyzed, suggesting that Sd-Bra might also have a role in Porifera morphogenesis.

Expression of one sponge Iroquois homeobox gene in primmorphs from Suberites domuncula during canal formation.

Sponges (Porifera) represent the evolutionary oldest multicellular animals. They are provided with the basic molecules involved in cell-cell and cell-matrix interactions. We report here the isolation and characterization of a complementary DNA from the sponge Suberites domuncula coding for the sponge homeobox gene, SUBDOIRX-a. The deduced polypeptide with a predicted Mr of 44,375 possesses the highly conserved Iroquois-homeodomain. We applied in situ hybridization to localize Iroquois in the sponge. The expression of this gene is highest in cells adjacent to the canals of the sponge in the medulla region. To study the expression of Iroquois during development, the in vitro primmorph system from S. domuncula was used. During the formation of these three-dimensional aggregates composed of proliferating cells, the expression of Iroquois depends on ferric iron and water current. An increased expression in response to water current is paralleled with the formation of canal-like pores in the primmorphs. It is suggested that Iroquois expression is involved in the formation of the aquiferous system, the canals in sponges and the canal-like structures in primmorphs.

Cultivation of primmorphs from the marine sponge Suberites domuncula: morphogenetic potential of silicon and iron.

Marine demosponges (phylum Porifera) are rich sources for potent bioactive compounds. With the establishment of the primmorph system from sponges, especially from Suberites domuncula, the technology to cultivate sponge cells in vitro improved considerably. This progress was possible after the elucidation that sponges are provided with characteristic metazoan cell adhesion receptors and extracellular matrix molecules which allow their cells a positioning in a complex organization pattern. This review summarizes recent data on the cultivation of sponges in aquaria and--with main emphasis--of primmorphs in vitro. It is outlined that silicon and Fe(+++) contribute substantially to the formation of larger primmorphs (size of 10 mm) as well as of a canal system in primmorphs; canals are probably required for an improved oxygen and food supply. We conclude that the primmorph system will facilitate a sustainable use of sponges in the production of bioactive compounds; it may furthermore allow new and hitherto not feasible insights into basic questions on the origin of Metazoa.

The molecular basis for the evolution of the metazoan bodyplan: extracellular matrix-mediated morphogenesis in marine demosponges.

Molecular data on development/differentiation and on comparative genomics allow insights into the genetic basis of the evolution of a bodyplan. Sponges (phylum Porifera) are animals that are the (still extant) stem group with the hypothetical Urmetazoa as the earliest common ancestor of all metazoans; they possess the basic features of the characteristic metazoan bodyplan also valid for the animals of the crown taxa. Here we describe three homeobox genes from the demosponge Suberites domuncula whose deduced proteins (HOXa1_SUBDO, HOXb1_SUBDO, HOXc1_SUBDO) are to be grouped with the Antennapedia class of homeoproteins (subclasses TIx-Hox11 and NK-2). In addition, a cDNA encoding a LIM/homeobox protein has been isolated which comprises high sequence similarity to the related LIM homeodomain (HD) proteins in its LIM as well as in its HD domains. To elucidate the potential function of these proteins in the sponge a new in vitro system was developed. Primmorphs which are formed from dissociated cells were grown on a homologous galectin matrix. This galectin cDNA was cloned and the recombinant protein was used for the preparation of the matrix. The galectin/polylysine matrix induced in primmorphs the formation of channels, one major morphogenetic process in sponges. Under such conditions the expression of the gene encoding the LIM/homeobox protein is strongly upregulated, while the expression of the other homeobox genes remains unchanged or is even downregulated. Competition experiments with galactosylceramides isolated from S. domuncula were performed. They revealed that a beta-galactosylceramide, named Sdgal-1, prevented the expression of the LIM gene on the galectin matrix, while Sdgal-2, a diglycosylceramide having a terminal alpha-glycosidically linked galactose, caused no effect on the formation of channels in primmorphs or on LIM expression. This study demonstrates for the first time that an extracellular matrix molecule, galectin, induces a morphogenetic process in sponges which is very likely caused by a LIM/homeobox protein. Furthermore, a new model is introduced (galectin-caused channel formation in sponge primmorphs) to investigate basic pathways, thus allowing new insights into the functional molecular evolution of Metazoa.

Conservation of the positions of metazoan introns from sponges to humans.

Sponges (phylum Porifera) are the phylogenetic oldest Metazoa still extant. They can be considered as reference animals (Urmetazoa) for the understanding of the evolutionary processes resulting in the creation of Metazoa in general and also for the metazoan gene organization in particular. In the marine sponge Suberites domuncula, genes encoding p38 and JNK kinases contain nine and twelve introns, respectively. Eight introns in both genes share the same positions and the identical phases. One p38 intron slipped for six bases and the JNK gene has three more introns. However, the sequences of the introns are not conserved and the introns in JNK gene are generally much longer. Introns interrupt most of the conserved kinase subdomains I-XI and are found in all three phases (0, 1 and 2). We analyzed in details p38 and JNK genes from human, Caenorhabditis elegans and Drosophila melanogaster and found in most genes introns at the positions identical to those in sponge genes. The exceptions are two p38 genes from D. melanogaster that have lost all introns in the coding sequence. The positions of 11 introns in each of four human p38 genes are fully conserved and ten introns occupy identical positions as the introns in sponge p38 or JNK genes. The same is true for nine, out of ten introns in the human JNK-1 gene. The introns in human p38 and JNK genes are on average more than ten times longer than corresponding introns in sponges. It was proposed that yeast HOG1-like kinases (from i.e. Saccharomyces cerevisiae and Emericella nidulans) and metazoan p38 and JNK kinases are orthologues. p38 and JNK genes were created after the split from fungi by the duplication and diversification of the HOG1-like progenitor gene. Our results further support the common origin of p38 and JNK genes and speak in favor of a very early time of duplication. The ancestral gene contained at least ten introns, which are still present at the very conserved positions in p38 and JNK genes of extant animals. Four of these introns are present at the same positions in the HOG-like gene in the fungus E. nidulans. The others probably entered the ancestral gene after the split of fungi, but before the duplication of the gene and before the creation of the common, urmetazoan progenitor of all multicellular animals. A second gene coding for an immune molecule is described, the allograft inflammatory factor, which likewise showed a highly conserved exon/intron structure in S. domuncula and in human. These data show that the intron/exon borders are highly conserved in genes from sponges to human.

Histocompatibility reaction in tissue and cells of the marine sponge Suberites domuncula in vitro and in vivo: central role of the allograft inflammatory factor 1.

Sponges (Porifera) are the phylogenetically oldest still extant metazoan phylum. Recently elements of their immune system have been cloned and analyzed, primarily from the demosponges Suberites domuncula and Geodia cydonium. By differential display, two genes were identified in S. domuncula, whose translation products are involved in graft rejection/fusion: the allograft inflammatory factor (AIF-1) and the Tcf-like transcription factor (TCF). Since the AIF-1 and TCF genes are upregulated in vivo after tissue transplantation, especially in allografts, we investigated whether this reaction can be monitored in vitro. Therefore, the autogeneic and the allogeneic mixed sponge cell reaction (MSCR) system was applied for the first time to identify distinct factors in sponges in vitro. The results confirm that the two AIF-1 and TCF genes are induced during allogeneic MSCR. Furthermore, the recombinant sponge AIF-1 causes an upregulation of the expression of the TCF. We conclude that the AIF-1 and TCF genes are upregulated in sponges during histoincompatibility reactions; the data support the view that sponges have immune systems composed of highly complex elements related to those found in mammalian systems.

Iron induces proliferation and morphogenesis in primmorphs from the marine sponge Suberites domuncula.

Dissociated cells from marine demosponges retain their proliferation capacity if they are allowed to form special aggregates, the primmorphs. On the basis of incorporation studies and septin gene expression, we show that Fe3+ ions are required for the proliferation of cells in primmorphs from Suberites domuncula. In parallel, Fe3+ induced the expression of ferritin and strongly stimulated the synthesis of spicules. This result is supported by the finding that the enzymatic activity of silicatein, converting organosilicon to silicic acid, depends on Fe3+. Moreover, the expression of a scavenger receptor molecule, possibly involved in the morphology of spicules, depends on the presence of Fe3+. We conclude that iron is an essential factor in proliferative and morphogenetic processes in primmorphs.

Induction of (2'-5')oligoadenylate synthetase in the marine sponges Suberites domuncula and Geodia cydonium by the bacterial endotoxin lipopolysaccharide.

Recent studies have shown that the Porifera, with the examples of the demosponges Suberites domuncula and Geodia cydonium, comprise a series of pathways found also in the immune system of Deuterostomia, such as vertebrates, but are absent in Protostomia, with insects or nematodes as examples. One pathway is the (2'-5')oligoadenylate synthetase [(2-5)A synthetase] system. In the present study we show that crude extracts from tissue of S. domuncula collected from the sea display a considerable amount of (2-5)A synthetase activity; 16% of the ATP substrate is converted to the (2-5)A product, while tissue from specimens which were kept for 6 months in an aquarium shows only 1% of conversion. As aquarium animals show a lower bacterial load, those specimens were treated for the experiments with the bacterial endotoxin lipopolysaccharide (LPS); they responded to LPS with a stimulation of the (2-5)A synthetase activity. To monitor if this effect can be obtained also on the in vitro level, primmorphs which comprise proliferating and differentiating cells, were incubated with LPS. Extracts obtained from LPS-treated primmorphs also convert ATP to the (2-5)A products mediated by the synthetase. In parallel to this effect on protein level, LPS causes after an incubation period of 12 h also an increase in the steady-state level of the transcripts encoding the putative (2-5)A synthetase. It is postulated that in sponges the (2-5)A synthetase is involved in antimicrobial defense of the animals.