title: Hypoxic survival requires a 2-on-2 hemoglobin in a process involving nitric oxide.
abstract: Hemoglobins are recognized today as a diverse family of proteins present in all kingdoms of life and performing multiple reactions beyond O2 chemistry. The physiological roles of most hemoglobins remain elusive. Here, we show that a 2-on-2 ("truncated") hemoglobin, termed THB8, is required for hypoxic growth and the expression of anaerobic genes in Chlamydomonas reinhardtii. THB8 is 1 of 12 2-on-2 hemoglobins in this species. It belongs to a subclass within the 2-on-2 hemoglobin class I family whose members feature a remarkable variety of domain arrangements and lengths. Posttranscriptional silencing of the THB8 gene results in the mis-regulation of several genes and a growth defect under hypoxic conditions. The latter is intensified in the presence of an NO scavenger, which also impairs growth of wild-type cells. As recombinant THB8 furthermore reacts with NO, the results of this study indicate that THB8 is part of an NO-dependent signaling pathway.
authors.affiliation: Fakultät für Biologie und Biotechnologie, Lehrstuhl für Biochemie der Pflanzen, AG Photobiotechnologie, Ruhr Universität Bochum, 44801 Bochum, Germany. anja.hemschemeier@rub.de
authors.forename: Anja
authors.initials: A
authors.lastname: Hemschemeier
authors.forename: Melis
authors.initials: M
authors.lastname: Düner
authors.forename: David
authors.initials: D
authors.lastname: Casero
authors.forename: Sabeeha S
authors.initials: SS
authors.lastname: Merchant
authors.forename: Martin
authors.initials: M
authors.lastname: Winkler
authors.forename: Thomas
authors.initials: T
authors.lastname: Happe
mesh_terms: D000595:Amino Acid Sequence; D000693:Anaerobiosis / Q000235:genetics; D015687:Cell Hypoxia / Q000235:genetics; D016825:Chlamydomonas reinhardtii / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D017343:Genes, Plant; D006454:Hemoglobins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009569:Nitric Oxide / Q000737:chemistry* / Q000502:physiology*; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference
chemical_list: D006454:Hemoglobins; D010940:Plant Proteins; D009569:Nitric Oxide
keywords: gene expression; hypoxia