Developmental expression and biochemical analysis of the Arabidopsis atao1 gene encoding an H2O2‐generating diamine oxidase

Summary A copper amine oxidase encoding gene, atao1, has been isolated and characterized from Arabidopsis thaliana. Sequence analysis reveals that atao1 encodes a 668 amino acid polypeptide (ATAO1) with 48% identity to copper amine oxidases from pea and lentil. The promoter region of atao1 was transcriptionally fused with the reporter genes encoding β‐glucuronidase and modified green fluorescent protein. Analysis of transgenic Arabidopsis together with in situ hybridization of wild‐type plants reveals temporally and spatially discrete patterns of gene expression in lateral root cap cells, vascular tissue of roots, developing leaves, the hypocotyl, and in the style/stigmatal tissue. Enzyme activity assays show that ATAO1 preferentially oxidizes the aliphatic diamine putrescine with production of the corresponding aldehyde, ammonia and hydrogen peroxide, a recognized plant signal molecule and substrate for peroxidases. Histochemical analysis reveals that atao1 expression in developing tracheary elements precedes and overlaps with lignification and therefore is a good marker for vascular development. In both vascular tissue and the root cap, atao1 expression occurs in cells destined to undergo programmed cell death.