NADPH oxidase genes from tomato (Lycopersicon esculentum) and curly-leaf pondweed (Potamogeton crispus)

The oxidative burst is an integral component of plant resistance to pathogens. There is accumulating evidence that the oxidative burst is catalyzed by an enzyme with similarities to the phagocyte NADPH oxidase. We have cloned a full length homolog of the gp91 (phox) subunit of the plasma membrane NADPH oxidase complex from tomato named LeRBOH1. The predicted protein contains 989 amino acids. The large N-terminal domain contains two EF hand calcium binding motifs and one conserved glycosylation site. Six putative membrane spans are present in the C-terminal half of the predicted protein. Extensive homology with the human gp91 (phox) subunit was found including conservation of amino acid residues important for heme coordination and substrate binding. We have also isolated partial genomic clones from tomato and from the aquatic plant Po-tamogeton crispus. These species serve as models for studies of signal transduction leading to NADPH oxidase activation. In tomato, LeRBOH1 expression was too low to be detected on Northern blots. RT-PCR indicated that LeRBOH1 was expressed in all tissues tested.