title: Evolution, three-dimensional model and localization of truncated hemoglobin PttTrHb of hybrid aspen.
abstract: Thus far, research on plant hemoglobins (Hbs) has mainly concentrated on symbiotic and non-symbiotic Hbs, and information on truncated Hbs (TrHbs) is scarce. The aim of this study was to examine the origin, structure and localization of the truncated Hb (PttTrHb) of hybrid aspen (Populus tremula L. × tremuloides Michx.), the model system of tree biology. Additionally, we studied the PttTrHb expression in relation to non-symbiotic class1 Hb gene (PttHb1) using RNAi-silenced hybrid aspen lines. Both the phylogenetic analysis and the three-dimensional (3D) model of PttTrHb supported the view that plant TrHbs evolved vertically from a bacterial TrHb. The 3D model suggested that PttTrHb adopts a 2-on-2 sandwich of α-helices and has a Bacillus subtilis -like ligand-binding pocket in which E11Gln and B10Tyr form hydrogen bonds to a ligand. However, due to differences in tunnel cavity and gate residue (E7Ala), it might not show similar ligand-binding kinetics as in Bs-HbO (E7Thr). The immunolocalization showed that PttTrHb protein was present in roots, stems as well as leaves of in vitro -grown hybrid aspens. In mature organs, PttTrHb was predominantly found in the vascular bundles and specifically at the site of lateral root formation, overlapping consistently with areas of nitric oxide (NO) production in plants. Furthermore, the NO donor sodium nitroprusside treatment increased the amount of PttTrHb in stems. The observed PttTrHb localization suggests that PttTrHb plays a role in the NO metabolism.
authors: Department of Biology, University of Oulu, Oulu, Finland ; UMR-MD1, Transporteurs Membranaires, Chimiorésistance et Drug-Design, Aix-Marseille Université, Marseille, France.
authors: Estelle
authors: E
authors: Dumont
authors: Department of Biology, University of Oulu, Oulu, Finland.
authors: Soile
authors: S
authors: Jokipii-Lukkari
authors: Structural Bioinformatics Laboratory, Department of Biosciences, Åbo Akademi University, Turku, Finland.
authors: Vimal
authors: V
authors: Parkash
authors: Department of Biology, University of Oulu, Oulu, Finland.
authors: Jaana
authors: J
authors: Vuosku
authors: Structural Bioinformatics Laboratory, Department of Biosciences, Åbo Akademi University, Turku, Finland.
authors: Robin
authors: R
authors: Sundström
authors: Structural Bioinformatics Laboratory, Department of Biosciences, Åbo Akademi University, Turku, Finland.
authors: Yvonne
authors: Y
authors: Nymalm
authors: Department of Biology, University of Oulu, Oulu, Finland.
authors: Suvi
authors: S
authors: Sutela
authors: Department of Biology, University of Oulu, Oulu, Finland.
authors: Katariina
authors: K
authors: Taskinen
authors: Institute of Microbiology, ETH-Zürich, Zürich, Switzerland.
authors: Pauli T
authors: PT
authors: Kallio
authors: Structural Bioinformatics Laboratory, Department of Biosciences, Åbo Akademi University, Turku, Finland.
authors: Tiina A
authors: TA
authors: Salminen
authors: Department of Biology, University of Oulu, Oulu, Finland.
authors: Hely
authors: H
authors: Häggman
mesh_terms: D000595:Amino Acid Sequence; D005075:Biological Evolution; D018506:Gene Expression Regulation, Plant; D006418:Heme / Q000737:chemistry / Q000378:metabolism; D006824:Hybridization, Genetic; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D018515:Plant Leaves / Q000378:metabolism; D018547:Plant Stems / Q000378:metabolism; D030821:Plants, Genetically Modified; D032107:Populus / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport; D034622:RNA Interference; D016415:Sequence Alignment; D040681:Structural Homology, Protein; D054793:Truncated Hemoglobins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D054793:Truncated Hemoglobins; D006418:Heme