RESUMEN
The coordinated expression of highly related homoeologous genes in polyploid species underlies the phenotypes of many of the world's major crops. Here we combine extensive gene expression datasets to produce a comprehensive, genome-wide analysis of homoeolog expression patterns in hexaploid bread wheat. Bias in homoeolog expression varies between tissues, with ~30% of wheat homoeologs showing nonbalanced expression. We found expression asymmetries along wheat chromosomes, with homoeologs showing the largest inter-tissue, inter-cultivar, and coding sequence variation, most often located in high-recombination distal ends of chromosomes. These transcriptionally dynamic genes potentially represent the first steps toward neo- or subfunctionalization of wheat homoeologs. Coexpression networks reveal extensive coordination of homoeologs throughout development and, alongside a detailed expression atlas, provide a framework to target candidate genes underpinning agronomic traits in wheat.
Asunto(s)
Regulación de la Expresión Génica de las Plantas , Poliploidía , Transcripción Genética , Triticum/genética , Pan , Perfilación de la Expresión Génica , Regulación del Desarrollo de la Expresión Génica , Genoma de Planta , ARN de Planta/genética , Análisis de Secuencia de ARN , Triticum/crecimiento & desarrolloRESUMEN
BACKGROUND: Cytochrome c peroxidase from Pseudomonas aeruginosa (PsCCP) represents a new class of peroxidases which work without the need to create a semi-stable free radical for catalysis. The enzyme is located in the bacterial periplasm where its likely function is to provide protection against toxic peroxides. The soluble 323-residue single polypeptide chain contains two covalent c-type haems with very different properties: one of them is a low-potential (-330 mV) centre where hydrogen peroxide is reduced (the peroxidatic site); the other is a high-potential (+320 mV) centre which feeds electrons to the peroxidatic site from soluble electron-shuttle proteins such as cytochrome c and azurin. RESULTS: The crystal structure of the oxidized form of PsCCP has been determined to 2.4 A resolution by multiple isomorphous replacement, and refined to an R-factor of 19.2%. PsCCP is organized into two domains, both of them containing a covalent c-haem in a structure reminiscent of class 1 cytochromes c. The domains are related by a quasi-twofold axis. The domain interface holds a newly discovered calcium-binding site with an unusual set of ligands. CONCLUSIONS: The likely function of the calcium site is to maintain the structural integrity of the enzyme and/or to modulate electron transfer between the two haem domains. The low-potential haem has two histidine axial ligands (His55 and His71) and the high-potential haem is ligated by His201 and Met275. There are no polar residues at the peroxidatic site in the inactive oxidized enzyme. The structure suggests that, in the half-reduced functional form of the enzyme, the low-potential haem has to shed His71 in order to make the enzyme catalytically competent. This process is likely to trigger a reorganization of the active site, and may introduce a new residues into the haem pocket.
Asunto(s)
Proteínas Bacterianas/química , Citocromo-c Peroxidasa/química , Modelos Moleculares , Conformación Proteica , Pseudomonas aeruginosa/enzimología , Secuencia de Aminoácidos , Sitios de Unión , Calcio/metabolismo , Catálisis , Cristalografía por Rayos X , Transporte de Electrón , Radicales Libres , Hemo/química , Hierro/química , Datos de Secuencia Molecular , Oxidación-Reducción , Peroxidasas/clasificación , Relación Estructura-ActividadRESUMEN
The nucleotide sequence of the gene encoding cytochrome c551 peroxidase from Pseudomonas aeruginosa is reported. The translated amino acid sequence differs from the sequence reported earlier by peptide mapping most significantly by the presence of a section containing an additional 20 residues. A number of minor differences are also evident. The new sequence translates to a protein containing 346 amino acids, the first 23 being typical of a hydrophobic leader peptide with a characteristic protease cleavage site.
Asunto(s)
Proteínas Bacterianas , Citocromo-c Peroxidasa/biosíntesis , Citocromo-c Peroxidasa/genética , Pseudomonas aeruginosa/enzimología , Pseudomonas aeruginosa/genética , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Southern Blotting , Clonación Molecular , Grupo Citocromo c/metabolismo , Escherichia coli/genética , Manduca/genética , Datos de Secuencia Molecular , Oligodesoxirribonucleótidos , Proteínas Recombinantes/biosíntesis , Mapeo Restrictivo , Homología de Secuencia de AminoácidoRESUMEN
A mutation of glycine to alanine at position 143 in the mitochondrial cytochrome b amino acid sequence of Blumeria graminis f. sp. tritici cosegregated with the QoI-resistant phenotype in a ratio of 1:1 in a cross between a sensitive and a resistant isolate. This mutation was used as a mitochondrial marker to determine whether mitochondrial inheritance in B. graminis was anisogamous, as in heterothallic Neurospora sp., or isogamous and hermaphroditic, as in Aspergillus nidulans. Segregation of mitochondrial genotypes in B. graminis f. sp. tritici was consistent with inheritance of mitochondria being hermaphroditic and isogamous, in that all ascospores from an individual cleistothecium had the same mitochondrial genotype and that either parent could act as the maternal parent of a cleistothecium. Within each cleistothecium, nuclear segregation occurred independently of mitochondrial inheritance, as shown by segregation of resistance to the fungicide triadimenol and by segregation of avirulences to the wheat cultivars Galahad (Pm2), Armada (Pm4b), and Holger (Pm6).