FdTonB is involved in the photoregulation of cellular morphology during complementary chromatic adaptation in Fremyella diplosiphon

• Published in: Microbiology (Society for General Microbiology) 2010-03, Vol.156 (3), p.731-741
• Main Authors: Pattanaik, Bagmi, Montgomery, Beronda L
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Bacteriology; Biogenesis of cell structures, supramolecular organization; Biological and medical sciences; Computational Biology; Cyanobacteria - genetics; Cyanobacteria - growth & development; Cyanobacteria - metabolism; Cyanobacteria - radiation effects; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Bacterial; Iron - metabolism; Light; Membrane Proteins - genetics; Membrane Proteins - metabolism; Microbiology; Microscopy, Confocal; Molecular Sequence Data; Mutation; Pigmentation; RNA, Bacterial - genetics; Sequence Alignment; Sequence Homology, Amino Acid
• ISSN: 1350-0872; 1465-2080
• DOI: 10.1099/mic.0.035410-0

1 Department of Energy, Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA 2 Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA We have characterized a Fremyella diplosiphon TonB protein (FdTonB) and investigated its function during complementary chromatic adaptation. Sequence similarity analysis of FdTonB (571 aa) led to identification of several conserved domains characteristic of TonB proteins, including an N-terminal transmembrane domain, a central proline-rich spacer and a C-terminal TonB-related domain (TBRD). We identified a novel glycine-rich domain containing (Gly-X) n repeats. To assess FdTonB function, we constructed a tonB mutant through homologous recombination based upon truncation of the central proline-rich spacer, glycine-rich domain and TBRD. Our tonB mutant exhibited an aberrant cellular morphology under green light, with expanded cell width compared to the parental wild-type (WT) strain. The cellular morphology of the tonB mutant recovered upon WT tonB expression. Interestingly, tonB expression was found to be independent of RcaE. As tonB and WT strains respond in the same way when grown under iron-replete versus iron-limited conditions, our results suggest that FdTonB is not involved in the classic TonB function of mediating cellular adaptation to iron limitation, but exhibits a novel function related to the photoregulation of cellular morphology in F. diplosiphon . Correspondence Beronda L. Montgomery montg133{at}msu.edu Abbreviations: AP, allophycocyanin; CCA, complementary chromatic adaptation; chl a ; chlorophyll a ; DIC, differential interference contrast microscopy, GL, green light; GRP, glycine-rich protein; PBP, phycobiliprotein; PBS, phycobilisome; PC, phycocyanin; PE, phycoerythrin; RL, red light; TBRD, TonB-related domain; WT, wild-type The GenBank Third Party Annotation (TPA) database accession number for the annotated nucleotide sequence reported in this paper is BK006919. Supplementary tables of primers and plasmids, and a supplementary figure, are available with the online version of this paper.