Six Arabidopsis thaliana homologues of the human respiratory burst oxidase (gp91phox)

An NADPH oxidase analogous to that in mammalian phagocytes has been hypothesized to produce reactive oxygen species (ROS) in the plant defence response. A. thaliana contains at least six gp91(phox) homologues, designated AtrbohA-F (A. thaliana Respiratory Burst Oxidase Homologues), which map to different positions. Transcripts of three of these genes can be detected in healthy plants by RNA gel blot analyses. The Atrboh gene products are closely related to gp91(phox) and the intron locations suggest a common evolutionary origin. A putative EF-hand Ca2+-binding motif in the extended N-terminal region of the Atrboh proteins suggests a direct regulatory effect of Ca2+ on the activity of the NADPH oxidase in plants.