title: Cloning and characterization of a heme oxygenase-2 gene from alfalfa (Medicago sativa L.).
abstract: Heme oxygenase (HO, EC 1.14.99.3) catalyzes the oxidation of heme and performs vital roles in plant development and stress responses. Two HO isozymes exist in plants. Between these, HO-1 is an oxidative stress-response protein, and HO-2 usually exhibited constitutive expression. Although alfalfa HO-1 gene (MsHO1) has been investigated previously, HO2 is still poorly understood. In this study, we report the cloning and characterization of HO2 gene, MsHO2, from alfalfa (Medica sativa L.). The full-length cDNA of MsHO2 contains an ORF of 870 bp and encodes for 290 amino acid residues with a predicted molecular mass of 33.3 kDa. Similar to MsHO1, MsHO2 also appears to have an N-terminal transit peptide sequence for chloroplast import. Many conserved residues in plant HO were also conserved in MsHO2. However, unlike HO-1, the conserved histidine (His) required for heme-iron binding and HO activity was replaced by tyrosine (Tyr) in MsHO2. Further biochemical activity analysis of purified mature MsHO2 showed no HO activity, suggesting that MsHO2 may not be a true HO in nature. Semi-quantitative RT-PCR confirmed its maximum expression in the germinating seeds. Importantly, the expression levels of MsHO2 were up-regulated under sodium nitroprusside (SNP) and H(2)O(2) (especially) treatment, respectively.
authors.affiliation: College of Life Sciences, Cooperative Demonstration Laboratory of Centrifuge Technique, Nanjing Agricultural University, Nanjing 210095, People's Republic of China.
authors.forename: Guang-Qing
authors.initials: GQ
authors.lastname: Fu
authors.forename: Qi-Jiang
authors.initials: QJ
authors.lastname: Jin
authors.forename: Yu-Ting
authors.initials: YT
authors.lastname: Lin
authors.forename: Jian-Fei
authors.initials: JF
authors.lastname: Feng
authors.forename: Li
authors.initials: L
authors.lastname: Nie
authors.forename: Wen-Biao
authors.initials: WB
authors.lastname: Shen
authors.forename: Tian-Qing
authors.initials: TQ
authors.lastname: Zheng
mesh_terms: D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D006419:Heme Oxygenase (Decyclizing) / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D000455:Medicago sativa / Q000737:chemistry / Q000145:classification / Q000201:enzymology* / Q000235:genetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D010944:Plants / Q000737:chemistry / Q000145:classification / Q000201:enzymology / Q000235:genetics; D016415:Sequence Alignment
chemical_list: D010940:Plant Proteins; D006419:Heme Oxygenase (Decyclizing); C105245:heme oxygenase-2