title: Anabaena sp. strain PCC 7120 conR contains a LytR-CpsA-Psr domain, is developmentally regulated, and is essential for diazotrophic growth and heterocyst morphogenesis.
abstract: The conR (all0187) gene of the filamentous cyanobacterium Anabaena (Nostoc) sp. strain PCC 7120 is predicted to be part of a family of proteins that contain the LytR-CpsA-Psr domain associated with septum formation and cell wall maintenance. The conR gene was originally misannotated as a transcription regulator. Northern RNA blot analysis showed that conR expression was upregulated 8 h after nitrogen step-down. Fluorescence microscopy of a P(conR)-gfp reporter strain revealed increased GFP fluorescence in proheterocysts and heterocysts beginning 9 h after nitrogen step-down. Insertional inactivation of conR caused a septum-formation defect of vegetative cells grown in nitrate-containing medium. In nitrate-free medium, mutant filaments formed abnormally long heterocysts and were defective for diazotrophic growth. Septum formation between heterocysts and adjacent vegetative cells was abnormal, often with one or both poles of the heterocysts appearing partially open. In a conR mutant, expression of nifH was delayed after nitrogen step-down and nitrogenase activity was approximately 70 % of wild-type activity, indicating that heterocysts of the conR mutant strain are partially functional. We hypothesize that the diazotrophic growth defect is caused by an inability of the heterocysts to transport fixed nitrogen to the neighbouring vegetative cells.
authors.affiliation: Division of Biological Sciences, University of California San Diego, La Jolla, CA 92093-0116, USA.|Department of Biology, Texas A&M University, College Station, TX 77843-3258, USA.
authors.forename: Rodrigo A
authors.initials: RA
authors.lastname: Mella-Herrera
authors.affiliation: Department of Biology, Texas A&M University, College Station, TX 77843-3258, USA.
authors.forename: M Ramona
authors.initials: MR
authors.lastname: Neunuebel
authors.affiliation: Division of Biological Sciences, University of California San Diego, La Jolla, CA 92093-0116, USA.
authors.forename: James W
authors.initials: JW
authors.lastname: Golden
mesh_terms: D017033:Anabaena / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism / Q000648:ultrastructure; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D002473:Cell Wall / Q000378:metabolism; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D008854:Microscopy, Electron; D009024:Morphogenesis; D016254:Mutagenesis, Insertional; D009154:Mutation; D009566:Nitrates / Q000378:metabolism / Q000494:pharmacology; D009584:Nitrogen / Q000378:metabolism; D009586:Nitrogen Fixation / Q000235:genetics / Q000502:physiology*; D020411:Oligonucleotide Array Sequence Analysis; D000644:Quaternary Ammonium Compounds / Q000378:metabolism / Q000494:pharmacology
chemical_list: D001426:Bacterial Proteins; D009566:Nitrates; D000644:Quaternary Ammonium Compounds; D049452:Green Fluorescent Proteins; D009584:Nitrogen