Identification and characterization of NADPH-oxidase genes in domestic apple (Malus × domestica Borkh.)

Many economically important plants used in horticulture, such as apple, pear, cherry, peach and strawberry, belongs to Rosaceae family. Apple is one of three model species of the Rosaceae family, therefore extensive genome information and knowledge on biology and genetics of apple became available recently. Plant cells contain superoxide anion producing NADPH oxidase enzyme, also known as respiratory burst oxidase (RBOH), of NOX protein family that is located in plasma membrane and contributes to generation of reactive oxygen species (ROS) that plays important role in cell signaling involved in plant development, abiotic stress response and pathogen defense. RBOH genes have been described in different plant species during last two decades. Arabidopsis thaliana genome contains ten AtRBOH genes (A-J) that demonstrate different expression levels and function in different plant tissues. A number of RBOH homologous genes has been identified in other plants. However, number and function of RBOH homologs in plants of Rosaceae family still remains unknown. Therefore this study was aimed to identify RBOH genes in apple (Malus × domestica Borkh.) and to characterize their expression in shoots grown under in vitro conditions. For identification and phylogenetic analysis of genes of apple RBOHs, protein sequences were retrieved by a similarity search. Query of the Apple predicted peptide database with the ten Arabidopsis RBOH orthologous protein sequences identified eight unique full-length sequence matches. Two genes that were annotated to code transcripts with only partial sequence coverage of RBOH protein were identified in apple genomic database. However, additional analysis using Fgenesh gene prediction algorithm resulted in assembly of single ninth sequence of MdRBOH gene. [...].