Identification of two metabolites induced by a butyrolactone autoregulator IM-2 in Streptomyces sp. FRI-5

Abstract In order to determine whether non-elastase-producing strains of Pseudomonas aeruginosa such as N-10, PA103 and IFO3080 can express foreign elastase genes, we introduced elastase genes from P. aeruginosa IFO3455 (elastase-producing) as well as from PA103 and N-10 into non-elastase-producing P. aeruginosa strains. Results suggested that gene expression, secretion, and precursor processing systems of elastase were essentially normal in P. aeruginosa N-10 and IFO3080. Our studies using various elastase genes showed that both the elastase structural gene and 5'-upstream regions of P. aeruginosa PA103 were also normal. This was confirmed by the finding that P. aeruginosa N-10 and IFO3080 which carry the PA103 elastase gene produced elastase. Several deleted or chimeric genes were constructed using the 5'-upstream regions of elastase genes from P. aeruginosa N-10 or PA103 and studies of expression revealed that two individual DNA bases seem to be important in suppressing P. aeruginosa N-10 elastase gene expression. Possible reasons for the lack of elastase in these non-elastase-producing strains are discussed.     

Overexpression of a non-native deoxyxylulose-dependent vitamin B6 pathway in Bacillus subtilis for the production of pyridoxine

Vitamin B6 is a designation for the vitamers pyridoxine, pyridoxal, pyridoxamine, and their respective 5′-phosphates. Pyridoxal 5′-phosphate, the biologically most-important vitamer, serves as a cofactor for many enzymes, mainly active in amino acid metabolism. While microorganisms and plants are capable of synthesizing vitamin B6, other organisms have to ingest it. The vitamer pyridoxine, which is used as a dietary supplement for animals and humans is commercially produced by chemical processes. The development of potentially more cost-effective and more sustainable fermentation processes for pyridoxine production is of interest for the biotech industry. We describe the generation and characterization of a Bacillus subtilis pyridoxine production strain overexpressing five genes of a non-native deoxyxylulose 5′-phosphate-dependent vitamin B6 pathway. The genes, derived from Escherichia coli and Sinorhizobium meliloti, were assembled to two expression cassettes and introduced into the B. subtilis chromosome. in vivo complementation assays revealed that the enzymes of this pathway were functionally expressed and active. The resulting strain produced 14 mg/l pyridoxine in a small-scale production assay. By optimizing the growth conditions and co-feeding of 4-hydroxy-threonine and deoxyxylulose the productivity was increased to 54 mg/l. Although relative protein quantification revealed bottlenecks in the heterologous pathway that remain to be eliminated, the final strain provides a promising basis to further enhance the production of pyridoxine using B. subtilis.     

Hbox1 and Hbox7 are involved in pattern formation in sea urchin embryos

In spite of their potential importance in evolution, there is little information about Hox genes in animal groups that are related to ancestors of deuterostome. It has been reported that only two Hox genes (Hbox1 and Hbox7) are expressed significantly in sea urchin embryos. Expression of Hbox1 protein is restricted to the aboral ectoderm, and Hbox7 expression is restricted to oral ectoderm, endoderm and secondary mesenchyme cells in sea urchin embryos after the gastrula stage. With the aim of gaining insight into the role of Hbox1 and Hbox7 in sea urchin development, Hbox1 and Hbox7 overexpression experiments were performed. Overexpression of Hbox1 repressed the development of oral ectoderm, endoderm and mesenchyme cells. On the contrary, overexpression of Hbox7 repressed the development of aboral ectoderm and primary mesenchyme cells. The data suggest that Hbox1 and Hbox7 are expressed in distinct non-overlapping territories, and overexpression of either one inhibits territory-specific gene expression in the domain of the other. It is proposed that an important function of both Hbox1 and Hbox7 genes is to maintain specific territorial gene expression by each one, in its domain of expression, while repressing the expression of the other in this same domain.     

Evolutionary trade-offs at the Arabidopsis WRR4A resistance locus underpin alternate Albugo candida race recognition specificities

The oomycete Albugo candida causes white rust of Brassicaceae, including vegetable and oilseed crops, and wild relatives such as Arabidopsis thaliana. Novel White Rust Resistance (WRR) genes from Arabidopsis enable new insights into plant/parasite co-evolution. WRR4A from Arabidopsis accession Columbia (Col-0) provides resistance to many but not all white rust races, and encodes a nucleotide-binding, leucine-rich repeat immune receptor. Col-0 WRR4A resistance is broken by AcEx1, an isolate of A. candida. We identified an allele of WRR4A in Arabidopsis accession Øystese-0 (Oy-0) and other accessions that confers full resistance to AcEx1. WRR4A^Oy-0 carries a C-terminal extension required for recognition of AcEx1, but reduces recognition of several effectors recognized by the WRR4A^Col-0 allele. WRR4A^Oy-0 confers full resistance to AcEx1 when expressed in the oilseed crop Camelina sativa.     

Molecular Co-occupancy Identifies Transcription Factor Binding Cooperativity In Vivo

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