Regulation of Cucumber Class III Chitinase Gene Expression. Kay A. Lawton. Department of Molecular Genetics, Ciba Agricultural Biotechnology, P.O. Box 12257, Research Triangle Park, NC 27709 U.S.A. James Beck, Sharon Potter, Eric Ward, and John Ryals. Department of Molecular Genetics, Ciba Agricultural Biotechnology, P.O. Box 12257, Research Triangle Park, NC 27709 U.S.A. MPMI 7:48-57. Accepted 21 October 1993. Copyright 1994 The American Phytopathological Society.

The chromosomal region encoding the acidic class III chitinase from cucumber has been isolated and characterized. A.s a result of an apparent gene triplication, the pathogen-induced gene (CHI2) is flanked by two closely related genes with complete open reading frames (ORF). The high level of conservation within the three ORFs suggests an essential role for each encoded protein in plant growth and development. The developmental and tissue-specific expression of RNA from each gene was analyzed using both gene-specific probes and RNA-PCR. The expression of each gene in response to various inducing treatments was also characterized. Only transcripts corresponding to CHI2 were delected. Chitinase mRNA abundance increased slightly following cycloheximide application; however, its potent induction by salicylic acid was inhibited by cycloheximide treatment.