title: Hemoglobin expression affects ethylene production in maize cell cultures.
abstract: The formation of ethylene under different O(2) concentrations and upon addition of nitric oxide (NO) donor, sodium nitroprusside (SNP), was determined using maize (Zea mays L.) cell lines over-expressing (Hb+) or down-regulating (Hb-) hypoxically inducible (class-1) hemoglobin (Hb). Under all treatments, ethylene levels in the Hb- line were 5 to 6.5 times the levels in Hb+ and four to five times the levels in the wild type. Low oxygen partial pressures impaired ethylene formation in maize cell suspension cultures. 1-Amino-cyclopropane-1-carboxylic acid (ACC) oxidase (E.C. 1.14.17.4) mRNA levels did not vary, either between lines or between treatments. There was, however, significantly enhanced ACC oxidase (ACO) activity in the Hb- line relative to the wild type and the Hb+ line. ACO activity in the Hb- line increased under hypoxic conditions and significantly increased upon treatment with NO under normoxic conditions. The results suggest that limiting class-1 hemoglobin protein synthesis increases ethylene formation in maize suspension cells, possibly via the modulation of NO levels.
authors.affiliation: Department of Plant Science, University of Manitoba, Winnipeg, Man., Canada R3T 2N2.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Manac'h-Little
authors.forename: Abir U
authors.initials: AU
authors.lastname: Igamberdiev
authors.forename: Robert D
authors.initials: RD
authors.lastname: Hill
mesh_terms: D000594:Amino Acid Oxidoreductases / Q000235:genetics / Q000378:metabolism; D018929:Cell Culture Techniques; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005030:Ethylenes / Q000096:biosynthesis*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D006454:Hemoglobins / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism; D009599:Nitroprusside / Q000494:pharmacology; D010100:Oxygen / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013997:Time Factors; D003313:Zea mays / Q000166:cytology / Q000235:genetics / Q000378:metabolism*
chemical_list: D005030:Ethylenes; D006454:Hemoglobins; D012333:RNA, Messenger; D009599:Nitroprusside; D009569:Nitric Oxide; C036216:ethylene; D000594:Amino Acid Oxidoreductases; C059460:1-aminocyclopropane-1-carboxylic acid oxidase; D010100:Oxygen