DIFFERENTIAL REGULATION OF AN AUXIN-PRODUCING NITRILASE GENE FAMILY IN ARABIDOPSIS-THALIANA

Nitrilases (nitrile aminohydrolase, EC 3.5.5.1) convert nitriles to ca rboxylic acids. We report the cloning, characterization, and expressio n patterns of four Arabidopsis thaliana nitrilase genes (NIT1-4), one of which was previously described [Bartling, D., Seedorf, M., Mithofer , A. and Weller, E. W. (1992) Eur. J. Biochem. 205, 417-424]. The nitr ilase genes encode very similar proteins that hydrolyze indole-3-aceto nitrile to the phytohormone indole-3-acetic acid in vitro, and three o f the four genes are tandemly arranged on chromosome III. Northern ana lysis using gene-specific probes and analysis of transgenic plants con taining promoter-reporter gene fusions indicate that the four genes ar e differentially regulated. NIT2 expression is specifically induced ar ound lesions caused by bacterial pathogen infiltration. The sites of n itrilase expression may represent sites of auxin biosynthesis in A. th aliana.