Regulación del metabolismo en Streptomyces: Control por ArgR

255 p.El metabolismo de arginina está reprimido por producto final en distintas bacterias, tanto Gram positivas como Gram negativas. Este efecto está mediado por ArgR, una proteína hexamérica que reprime los genes de biosíntesis de arginina utilizando L-arginina como corepresor. Esto ocurre en organismos como Escherichia coli, Pseudomonas, Bacillus subtilis, Lactococcus, Corynebacterium, etc. También es así en las distintas especies de Streptomyces. Dicha regulación se lleva a cabo mediante la unión de ArgR a las cajas ARG, constituidas por una secuencia palindrómica de 20 pb. La comparación transcriptómica mediante micromatrices llevada a cabo entre Streptomyces coelicolor M145 y su mutante S. coelicolor ¿argR en medio MG dio como resultado una transcripción diferencial de 1544 genes cuando se utiliza un valor p<0,01. En muchos casos el efecto se debe a la unión directa de ArgR a cajas ARG, pero a veces es indirecto a través de la regulación de la expresión de reguladores, factores sigma y anti-sigma. Los resultados indican que ArgR regula el metabolismo de arginina y otros aminoácidos, de purinas y pirimidinas y afecta al metabolismo del nitrógeno, a la producción de antibióticos (undecilprodigiosina y actinorrodina). La ausencia de ArgR también disminuye los niveles de los transcritos de las agrupaciones génicas para el poliquétido de tipo I CPK y el antibiótico dependiente de calcio CDA. ArgR afecta a la expresión de genes que codifican distintas proteínas de secreción y proteínas de membrana, genes implicados en la formación de estructuras celulares, morfología y esporulación. Afecta a la expresión de múltiples sistemas de dos componentes y transportadores ABC, a la síntesis de coenzimas, y a muchos genes implicados en la producción y conversión de energía, el transporte y metabolismo de carbohidratos y lípidos, entre otras funciones

Molecular genetics of naringenin biosynthesis, a typical plant secondary metabolite produced by Streptomyces clavuligerus

Background: Some types of flavonoid intermediates seemed to be restricted to plants. Naringenin is a typical plant metabolite, that has never been reported to be produced in prokariotes. Naringenin is formed by the action of a chal cone synthase using as starter 4-coumaroyl-CoA, which in dicotyledonous plants derives from phenylalanine by the action of a phenylalanine ammonia lyase. Results: A compound produced by Streptomyces clavuligerus has been identified by LC–MS and NMR as naringenin and coelutes in HPLC with a naringenin standard. Genome mining of S. clavuligerus revealed the presence of a gene for a chalcone synthase (ncs), side by side to a gene encoding a P450 cytochrome (ncyP) and separated from a gene encoding a Pal/Tal ammonia lyase (tal). Deletion of any of these genes results in naringenin non producer mutants. Complementation with the deleted gene restores naringenin production in the transformants. Furthermore, narin genin production increases in cultures supplemented with phenylalanine or tyrosine. Conclusion: This is the first time that naringenin is reported to be produced naturally in a prokariote. Interestingly three non-clustered genes are involved in naringenin production, which is unusual for secondary metabolites. A ten tative pathway for naringenin biosynthesis has been proposed

ArgR of Streptomyces coelicolor is a versatile regulator

[EN] ArgR is the regulator of arginine biosynthesis genes in Streptomyces species. Transcriptomic comparison by microarrays has been made between Streptomyces coelicolor M145 and its mutant S. coelicolor ΔargR under control, unsupplemented conditions, and in the presence of arginine. Expression of 459 genes was different in transcriptomic assays, but only 27 genes were affected by arginine supplementation. Arginine and pyrimidine biosynthesis genes were derepressed by the lack of ArgR, while no strong effect on expression resulted on arginine supplementation. Several nitrogen metabolism genes expression as glnK, glnA and glnII, were downregulated in S. coelicolor ΔargR. In addition, downregulation of genes for the yellow type I polyketide CPK antibiotic and for the antibiotic regulatory genes afsS and scbR was observed. The transcriptomic data were validated by either reverse transcription-PCR, expression of the gene-promoter coupled to the luciferase gene, proteomic or by electrophoresis mobility shift assay (EMSA) using pure Strep-tagged ArgR. Two ARG-boxes in the arginine operon genes suggest that these genes are more tightly controlled. Other genes, including genes encoding regulatory proteins, possess a DNA sequence formed by a single ARG-box which responds to ArgR, as validated by EMSASIThis work was supported by Grants from the Spanish Comisión Interministerial de Ciencia y Tecnología GEN2003-20245, BIO2009-09820, and by the European Project LSHM-CT-2004-005224. AB received a fellowship from the Ministry of Science and Innovation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

ArgR of Streptomyces coelicolor is a pleiotropic transcriptional regulator: effect on the transcriptome, antibiotic production, and differentiation in liquid cultures

[EN] ArgR is a well-characterized transcriptional repressor controlling the expression of arginine and pyrimidine biosynthetic genes in bacteria. In this work, the biological role of Streptomyces coelicolor ArgR was analyzed by comparing the transcriptomes of S. coelicolor ΔargR and its parental strain, S. coelicolor M145, at five different times over a 66-h period. The effect of S. coelicolor ArgR was more widespread than that of the orthologous protein of Escherichia coli, affecting the expression of 1544 genes along the microarray time series. This S. coelicolor regulator repressed the expression of arginine and pyrimidine biosynthetic genes, but it also modulated the expression of genes not previously described to be regulated by ArgR: genes involved in nitrogen metabolism and nitrate utilization; the act, red, and cpk genes for antibiotic production; genes for the synthesis of the osmotic stress protector ectoine; genes related to hydrophobic cover formation and sporulation (chaplins, rodlins, ramR, and whi genes); all the cwg genes encoding proteins for glycan cell wall biosynthesis; and genes involved in gas vesicle formation. Many of these genes contain ARG boxes for ArgR binding. ArgR binding to seven new ARG boxes, located upstream or near the ectA-ectB, afsS, afsR, glnR, and redH genes, was tested by DNA band-shift assays. These data and those of previously assayed fragments permitted the construction of an improved model of the ArgR binding site. Interestingly, the overexpression of sporulation genes observed in the ΔargR mutant in our culture conditions correlated with a sporulation-like process, an uncommon phenotypeSIGrant BIO2013-34723 from the Spanish Ministry of Science and Innovation to PL. Work in the AM's laboratory was funded by the European Research Council (ERC Starting Grant; Strp-differentiation 280304) and by the Spanish Ministry of Economy and Competitiveness (Grant BIO2015-65709-R)