title: Functional specialization of maize mitochondrial aldehyde dehydrogenases.
abstract: The maize (Zea mays) rf2a and rf2b genes both encode homotetrameric aldehyde dehydrogenases (ALDHs). The RF2A protein was shown previously to accumulate in the mitochondria. In vitro import experiments and ALDH assays on mitochondrial extracts from rf2a mutant plants established that the RF2B protein also accumulates in the mitochondria. RNA gel-blot analyses and immunohistolocation experiments revealed that these two proteins have only partially redundant expression patterns in organs and cell types. For example, RF2A, but not RF2B, accumulates to high levels in the tapetal cells of anthers. Kinetic analyses established that RF2A and RF2B have quite different substrate specificities; although RF2A can oxidize a broad range of aldehydes, including aliphatic aldehydes and aromatic aldehydes, RF2B can oxidize only short-chain aliphatic aldehydes. These two enzymes also have different pH optima and responses to changes in substrate concentration. In addition, RF2A, but not RF2B or any other natural ALDHs, exhibits positive cooperativity. These functional specializations may explain why many species have two mitochondrial ALDHs. This study provides data that serve as a basis for identifying the physiological pathway by which the rf2a gene participates in normal anther development and the restoration of Texas cytoplasm-based male sterility. For example, the observations that Texas cytoplasm anthers do not accumulate elevated levels of reactive oxygen species or lipid peroxidation and the kinetic features of RF2A make it unlikely that rf2a restores fertility by preventing premature programmed cell death.
authors.affiliation: Department of Zoology and Genetics, Iowa State University, Ames, Iowa 50011, USA.
authors.forename: Feng
authors.initials: F
authors.lastname: Liu
authors.forename: Patrick S
authors.initials: PS
authors.lastname: Schnable
mesh_terms: D000079:Acetaldehyde / Q000378:metabolism; D000444:Aldehyde Dehydrogenase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D050976:Basic-Leucine Zipper Transcription Factors; D035264:Flowers / Q000235:genetics / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D007210:Indoleacetic Acids / Q000378:metabolism; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D015227:Lipid Peroxidation; D008928:Mitochondria / Q000201:enzymology*; D024101:Mitochondrial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015534:Trans-Activators; D003313:Zea mays / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism
chemical_list: D050976:Basic-Leucine Zipper Transcription Factors; D007210:Indoleacetic Acids; D007527:Isoenzymes; D024101:Mitochondrial Proteins; D009687:Nuclear Proteins; D010940:Plant Proteins; D018749:RNA, Plant; D017382:Reactive Oxygen Species; D011994:Recombinant Proteins; D015534:Trans-Activators; C030737:indoleacetic acid; D000444:Aldehyde Dehydrogenase; D000079:Acetaldehyde