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Abstract Background The Batrachoididae family is a group of marine teleosts that includes several species with more complicated physiological characteristics, such as their excretory, reproductive, cardiovascular and respiratory systems. Previous studies of the 5S rDNA gene family carried out in four species from the Western Atlantic showed two types of this gene in two species but only one in the other two, under processes of concerted evolution and birth-and-death evolution with purifying selection. Here we present results of the 5S rDNA and another two gene families in Halobatrachus didactylus, an Eastern Atlantic species, and draw evolutionary inferences regarding the gene families. In addition we have also mapped the genes on the chromosomes by two-colour fluorescence in situ hybridization (FISH). Results Two types of 5S rDNA were observed, named type α and type β. Molecular analysis of the 5S rDNA indicates that H. didactylus does not share the non-transcribed spacer (NTS) sequences with four other species of the family; therefore, it must have evolved in isolation. Amplification with the type β specific primers amplified a specific band in 9 specimens of H. didactylus and two of Sparus aurata. Both types showed regulatory regions and a secondary structure which mark them as functional genes. However, the U2 snRNA gene and the ITS-1 sequence showed one electrophoretic band and with one type of sequence. The U2 snRNA sequence was the most variable of the three multigene families studied. Results from two-colour FISH showed no co-localization of the gene coding from three multigene families and provided the first map of the chromosomes of the species. Conclusions A highly significant finding was observed in the analysis of the 5S rDNA, since two such distant species as H. didactylus and Sparus aurata share a 5S rDNA type. This 5S rDNA type has been detected in other species belonging to the Batrachoidiformes and Perciformes orders, but not in the Pleuronectiformes and Clupeiformes orders. Two hypotheses have been outlined: one is the possible vertical permanence of the shared type in some fish lineages, and the other is the possibility of a horizontal transference event between ancient species of the Perciformes and Batrachoidiformes orders. This finding opens a new perspective in fish evolution and in the knowledge of the dynamism of the 5S rDNA. Cytogenetic analysis allowed some evolutionary trends to be roughed out, such as the progressive change in the U2 snDNA and the organization of (GATA)n repeats, from dispersed to localized in one locus. The accumulation of (GATA)n repeats in one chromosome pair could be implicated in the evolution of a pair of proto-sex chromosomes. This possibility could situate H. didactylus as the most highly evolved of the Batrachoididae family in terms of sex chromosome biology.

Abstract Background Molecular and cytogenetic markers are of great use for to fish characterization, identification, phylogenetics and evolution. Multigene families have proven to be good markers for a better understanding of the variability, organization and evolution of fish species. Three different tandemly-repeated gene families (45S rDNA, 5S rDNA and U2 snDNA) have been studied in Plectorhinchus mediterraneus (Teleostei: Haemulidae), at both molecular and cytogenetic level, to elucidate the taxonomy and evolution of these multigene families, as well as for comparative purposes with other species of the family. Results Four different types of 5S rDNA were obtained; two of them showed a high homology with that of Raja asterias, and the putative implication of a horizontal transfer event and its consequences for the organization and evolution of the 5S rDNA have been discussed. The other two types do not resemble any other species, but in one of them a putative tRNA-derived SINE was observed for the first time, which could have implications in the evolution of the 5S rDNA. The ITS-1 sequence was more related to a species of another different genus than to that of the same genus, therefore a revision of the Hamulidae family systematic has been proposed. In the analysis of the U2 snDNA, we were able to corroborate that U2 snDNA and U5 snDNA were linked in the same tandem array, and this has interest for tracing evolutionary lines. The karyotype of the species was composed of 2n = 48 acrocentric chromosomes, and each of the three multigene families were located in different chromosome pairs, thus providing three different chromosomal markers. Conclusions Novel data can be extracted from the results: a putative event of horizontal transfer, a possible tRNA-derived SINE linked to one of the four 5S rDNA types characterized, and a linkage between U2 and U5 snDNA. In addition, a revision of the taxonomy of the Haemulidae family has been suggested, and three cytogenetic markers have been obtained. Some of these results have not been described before in any other fish species. New clues about the genome organization and evolution of the multigene families are offered in this study.

Abstract Background The transition from exponential to stationary phase in Streptomyces coelicolor is accompanied by a major metabolic switch and results in a strong activation of secondary metabolism. Here we have explored the underlying reorganization of the metabolome by combining computational predictions based on constraint-based modeling and detailed transcriptomics time course observations. Results We reconstructed the stoichiometric matrix of S. coelicolor, including the major antibiotic biosynthesis pathways, and performed flux balance analysis to predict flux changes that occur when the cell switches from biomass to antibiotic production. We defined the model input based on observed fermenter culture data and used a dynamically varying objective function to represent the metabolic switch. The predicted fluxes of many genes show highly significant correlation to the time series of the corresponding gene expression data. Individual mispredictions identify novel links between antibiotic production and primary metabolism. Conclusion Our results show the usefulness of constraint-based modeling for providing a detailed interpretation of time course gene expression data.

Abstract Background During the lifetime of a fermenter culture, the soil bacterium S. coelicolor undergoes a major metabolic switch from exponential growth to antibiotic production. We have studied gene expression patterns during this switch, using a specifically designed Affymetrix genechip and a high-resolution time-series of fermenter-grown samples. Results Surprisingly, we find that the metabolic switch actually consists of multiple finely orchestrated switching events. Strongly coherent clusters of genes show drastic changes in gene expression already many hours before the classically defined transition phase where the switch from primary to secondary metabolism was expected. The main switch in gene expression takes only 2 hours, and changes in antibiotic biosynthesis genes are delayed relative to the metabolic rearrangements. Furthermore, global variation in morphogenesis genes indicates an involvement of cell differentiation pathways in the decision phase leading up to the commitment to antibiotic biosynthesis. Conclusions Our study provides the first detailed insights into the complex sequence of early regulatory events during and preceding the major metabolic switch in S. coelicolor, which will form the starting point for future attempts at engineering antibiotic production in a biotechnological setting.