title: Two hemoglobin genes in Arabidopsis thaliana: the evolutionary origins of leghemoglobins.
abstract: We cloned two hemoglobin genes from Arabidopsis thaliana. One gene, AHB1, is related in sequence to the family of nonsymbiotic hemoglobin genes previously identified in a number of plant species (class 1). The second hemoglobin gene, AHB2, represents a class of nonsymbiotic hemoglobin (class 2) related in sequence to the symbiotic hemoglobin genes of legumes and Casuarina. The properties of these two hemoglobins suggest that the two families of nonsymbiotic hemoglobins may differ in function from each other and from the symbiotic hemoglobins. AHB1 is induced, in both roots and rosette leaves, by low oxygen levels. Recombinant AHB1 has an oxygen affinity so high as to make it unlikely to function as an oxygen transporter. AHB2 is expressed at a low level in rosette leaves and is low temperature-inducible. AHB2 protein has a lower affinity for oxygen than AHB1 but is similar to AHB1 in having an unusually low, pH-sensitive oxygen off-rate.
authors.affiliation: Cooperative Research Centre for Plant Cell Biology, Australian National University, Australian Capital Territory, 2601 Australia.
authors.forename: B
authors.initials: B
authors.lastname: Trevaskis
authors.forename: R A
authors.initials: RA
authors.lastname: Watts
authors.forename: C R
authors.initials: CR
authors.lastname: Andersson
authors.forename: D J
authors.initials: DJ
authors.lastname: Llewellyn
authors.forename: M S
authors.initials: MS
authors.lastname: Hargrove
authors.forename: J S
authors.initials: JS
authors.lastname: Olson
authors.forename: E S
authors.initials: ES
authors.lastname: Dennis
authors.forename: W J
authors.initials: WJ
authors.lastname: Peacock
mesh_terms: D000595:Amino Acid Sequence; D000693:Anaerobiosis; D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins; D003001:Cloning, Molecular; D019143:Evolution, Molecular; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D006454:Hemoglobins / Q000235:genetics* / Q000378:metabolism; D007874:Leghemoglobin / Q000235:genetics*; D008969:Molecular Sequence Data; D010100:Oxygen / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics; D018517:Plant Roots / Q000378:metabolism; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution
chemical_list: C470347:AHB1 protein, Arabidopsis; C109042:AHB2 protein, Arabidopsis; D029681:Arabidopsis Proteins; D006454:Hemoglobins; D007874:Leghemoglobin; D010940:Plant Proteins; D010100:Oxygen