title: Post-transcriptional regulation of the alginate biosynthetic gene algD by the Gac/Rsm system in Azotobacter vinelandii.
abstract: Azotobacter vinelandii is a soil bacterium that produces the polysaccharide alginate. The two-component system GacS/GacA is required for alginate synthesis since a mutation in gacS or gacA significantly reduced the level of transcripts of algD, the gene encoding GDP-mannose dehydrogenase, a key enzyme of the alginate biosynthetic pathway. In many γ-proteobacteria, GacA homologs control the expression of small regulatory RNAs of the RsmZ/Y/X (CsrB/CsrC) family that interact with RsmA (CsrA) proteins. These proteins bind to their target mRNAs acting as translational repressors. The interaction of Rsm/Csr small RNAs with RsmA/CsrA counteract its repressor activity. In this study, one rsmA gene, seven rsmZ and two rsmY homologs were identified in the A. vinelandii genome. Two of the rsmZ homologs, named rsmZ1 and rsmZ2, together with rsmA, were characterized. Northern blot analysis was carried out to show that in A. vinelandii, GacA activates rsmZ1 and rsmZ2 transcription. We also showed that either overexpression of rsmA or inactivation of rsmZ1 or rsmZ2 diminished the production of alginate. In addition, interaction of RsmA with RsmZ1, RsmZ2 and the algD mRNA was demonstrated in vitro. These results show that GacS/A regulates alginate biosynthesis by post-transcriptional control of algD expression through the Rsm system.
authors.affiliation: Centro de Investigaciones en Ciencias Microbiológicas, Instituto de Ciencias, Benemérita Universidad Autónoma de Puebla, Puebla, México.
authors.forename: Joaquín
authors.initials: J
authors.lastname: Manzo
authors.forename: Miguel
authors.initials: M
authors.lastname: Cocotl-Yañez
authors.forename: Tomás
authors.initials: T
authors.lastname: Tzontecomani
authors.forename: Verónica M
authors.initials: VM
authors.lastname: Martínez
authors.forename: Rocío
authors.initials: R
authors.lastname: Bustillos
authors.forename: Claudia
authors.initials: C
authors.lastname: Velásquez
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Goiz
authors.forename: Yuri
authors.initials: Y
authors.lastname: Solís
authors.forename: Liliana
authors.initials: L
authors.lastname: López
authors.forename: Luis E
authors.initials: LE
authors.lastname: Fuentes
authors.forename: Cinthia
authors.initials: C
authors.lastname: Nuñez
authors.forename: Daniel
authors.initials: D
authors.lastname: Segura
authors.forename: Guadalupe
authors.initials: G
authors.lastname: Espín
authors.forename: Miguel
authors.initials: M
authors.lastname: Castañeda
mesh_terms: D000464:Alginates; D016948:Azotobacter vinelandii / Q000235:genetics*; D001426:Bacterial Proteins / Q000378:metabolism*; D001483:Base Sequence; D015152:Blotting, Northern; D002237:Carbohydrate Dehydrogenases / Q000378:metabolism*; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D020723:Glucuronic Acid / Q000096:biosynthesis; D006603:Hexuronic Acids; D008969:Molecular Sequence Data; D014176:Protein Biosynthesis; D058727:RNA, Small Untranslated / Q000378:metabolism*; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic
chemical_list: D000464:Alginates; D001426:Bacterial Proteins; C091100:GacA protein, Bacteria; D006603:Hexuronic Acids; D058727:RNA, Small Untranslated; D020723:Glucuronic Acid; D002237:Carbohydrate Dehydrogenases; C020562:GDPmannose dehydrogenase