Exploring the effect of microsatellite size homoplasy on reconstruction of phylogenetic relationships of picote splitfin Zoogoneticus quitzeoensis.

This study explores the effects of microsatellite size homoplasies on the reconstruction of phylogenetic relationships and estimates of population parameters as the fixation index (F(ST) ) using as a case study a truncated microsatellite from the picote splitfin Zoogoneticus quitzeoensis. The results suggest that the use of imperfect microsatellites may have only a minor effect in phylogenetic and population studies.

Nucleotide sequence and deduced functions of a set of cotranscribed genes of Streptomyces coelicolor A3(2) including the polyketide synthase for the antibiotic actinorhodin.

A 5.3-kb region of the Streptomyces coelicolor actinorhodin gene cluster, including the genes for polyketide biosynthesis, was sequenced. Six identified open reading frames (ORF1-6) were related to genetically characterized mutations of classes actI, VII, IV, and VB by complementation analysis. ORF1-6 run divergently from the adjacent actIII gene, which encodes the polyketide synthase (PKS) ketoreductase, and appear to form an operon. The deduced gene products of ORF1-3 are similar to fatty acid synthases (FAS) of different organisms and PKS genes from other polyketide producers. The predicted ORF5 gene product is similar to type II beta-lactamases of Bacillus cereus and Bacteroides fragilis. The ORF6 product does not resemble other known proteins. Combining the genetical, biochemical, and similarity data, the potential activities of the products of the six genes can be postulated as: 1) condensing enzyme/acyl transferase (ORF1 + ORF2); 2) acyl carrier protein (ORF3); 3) putative cyclase/dehydrase (ORF4); 4) dehydrase (ORF5); and 5) "dimerase" (ORF6). The data show that the actinorhodin PKS consists of discrete monofunctional components, like that of the Escherichia coli (Type II) FAS, rather than the multifunctional polypeptides for the macrolide PKSs and vertebrate FASs (Type I).

Biochemical and morphological effects of sodium butyrate on Dictyostelium discoideum development.

Pretreatment of proliferating D. discoideum amoebae with 10 mM butyrate for at least 8 h (one duplicating time) induced a reversible and dose dependent premature expression of several developmental parameters when the cells were starved in the absence of the fatty acid. The aggregative phase of the morphogenetic cycle was reduced in 2 h and the appearance of mature fruiting bodies and spores took place 4 h earlier as a result of butyrate pretreatment. Some developmentally regulated proteins, such as contact-sites A, cell surface lectins and cyclic AMP phosphodiesterase were also expressed 2 h earlier in butyrate pretreated cells than in controls. The level of extracellular cyclic AMP was reduced in butyrate pretreated cells, while other parameters of cyclic AMP metabolism were not affected. Butyrate also caused a partial inhibition of growth and the hyperacetylation of histone H4 in growing amoeba. These results suggest that butyrate acts as an inducer of differentiation in D. discoideum and can therefore be used as an experimental tool in order to explore regulatory mechanisms operating in slime mold differentiation.

Fructose 2,6-bisphosphate in Dictyostelium discoideum. Independence of cyclic AMP production and inhibition of fructose-1,6-bisphosphatase.

The occurrence of fructose 2,6-bisphosphate was detected in Dictyostelium discoideum. The levels of this compound were compared with those of cyclic AMP and several glycolytic intermediates during the early stages of development. Removal of the growth medium and resuspension of the organism in the differentiation medium decreased the content of fructose 2,6-bisphosphate to about 20% within 1 h, remaining low when starvation-induced development was followed for 8 h. The content of cyclic AMP exhibited a transient increase that did not correlate with the change in fructose 2,6-bisphosphate. If after 1 h of development 2% glucose was added to the differentiation medium, fructose 2,6-bisphosphate rapidly rose to similar levels to those found in the vegetative state, while the increase in cyclic AMP was prevented. The contents of hexose 6-phosphates, fructose 1,6-bisphosphate and triose phosphates changed in a way that was parallel to that of fructose 2,6-bisphosphate, and addition of sugar resulted in a large increase in the levels of these metabolites. The content of fructose 2,6-bisphosphate was not significantly modified by the addition of the 8-bromo or dibutyryl derivatives of cyclic AMP to the differentiation medium. These results provide evidence that the changes in fructose 2,6-bisphosphate levels in D. discoideum development are not related to a cyclic-AMP-dependent mechanism but to the availability of substrate. Fructose 2,6-bisphosphate was found to inhibit fructose-1,6-bisphosphatase activity of this organism at nanomolar concentrations, while it does not affect the activity of phosphofructokinase in the micromolar range. The possible physiological implications of these phenomena are discussed.

Short term regulation by lysine of ornithine decarboxylase activity in Dictyostelium discoideum.

A transitory increase in ornithine decarboxylase activity has been observed soon after food removal from Dictyostelium discoideum amoeba. This increase can be prevented by supplementation of the differentiation buffer with the 11 amino acids known for their ability to retard the development of this slime mold. Lysine can replace the amino acid mixture with an apparent inhibition constant of 50 micromolar. This inhibition by lysine, which was only observed in vivo, took place within 5 min and was readily reversed upon lysine removal.