title: Sucrose synthase and RuBisCo expression is similarly regulated by the nitrogen source in the nitrogen-fixing cyanobacterium Anabaena sp.
abstract: In higher plants and cyanobacteria, sucrose (Suc) metabolism is carried out by a similar set of enzymes. The function and regulation of Suc metabolism in cyanobacteria has begun to be elucidated. In strains of Anabaena sp., filamentous nitrogen-fixing cyanobacteria, Suc synthase (SuS, EC 2.4.1.13) controls Suc cell level through the cleavage of the disaccharide. The present work shows that there are two sus genes in Anabaena (Nostoc) sp. that are co-regulated regarding the nitrogen source; however, only susA accounts for the extractable SuS activity and for the control of the Suc level. Primer extension analysis has uncovered the sequence of the Anabaena susA and susB ammonium-activated putative promoters, which share a high sequence similarity with that of rbcLS encoding ribulose bisphosphate carboxylase/oxygenase (EC 4.1.1.39) and other ammonium up-regulated genes. Moreover, susA and rbcLS expression is developmentally co-localized to the vegetative cells of the nitrogen-fixing cyanobacterial filaments. Our results strongly suggest the existence of a regulatory network that would coordinate the expression of key genes for Suc and nitrogen metabolism, carbon fixation, and development in Anabaena sp.
authors.affiliation: Centro de Investigaciones Biológicas, Fundación para Investigaciones Biológicas Aplicadas, FIBA, CC 1348, 7600, Mar del Plata, Argentina.
authors.forename: Leonardo
authors.initials: L
authors.lastname: Curatti
authors.forename: Laura
authors.initials: L
authors.lastname: Giarrocco
authors.forename: Graciela L
authors.initials: GL
authors.lastname: Salerno
mesh_terms: D017033:Anabaena / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D001483:Base Sequence; D017931:DNA Primers; D015536:Down-Regulation; D015870:Gene Expression / Q000187:drug effects; D020868:Gene Silencing; D005964:Glucosyltransferases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009584:Nitrogen / Q000378:metabolism*; D009586:Nitrogen Fixation; D011401:Promoter Regions, Genetic; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology*; D050436:Regulatory Elements, Transcriptional; D012273:Ribulose-Bisphosphate Carboxylase / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D013395:Sucrose / Q000378:metabolism*; D024363:Transcription Initiation Site
chemical_list: D017931:DNA Primers; D000644:Quaternary Ammonium Compounds; D013395:Sucrose; D005964:Glucosyltransferases; C022699:sucrose synthase; D012273:Ribulose-Bisphosphate Carboxylase; D009584:Nitrogen