Virus-Induced Gene Expression for Enzymes of Ethylene Biosynthesis in Hypersensitively Reacting Tobacco. Marga Knoester . Institute of Molecular Plant Sciences, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands. John F. Bol, Leendert C. van Loon(1), and Huub J.M. Linthorst. Institute of Molecular Plant Sciences, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands; (1)Department of Plant Ecology and Evolutionary Biology, Utrecht University, P.O. Box 80084, 3508 TB Utrecht, The Netherlands. MPMI 8:177-180. Accepted 13 October 1994 . Copyright 1995 The American Phytopathological Society.

A full-length cDNA clone (cEFE-26) encoding ethylene-forming enzyme (EFE) was isolated from a cDNA library, prepared from leaves of tobacco mosaic virus (TMV)-in-fected tobacco cultivar Samsun NN. The cDNA clone encodes a protein with 90% amino acid sequence similarity to established EFEs of tomato and other plants. By using cEFE-26 cDNA and the insert from cDNA clone pACC13 (B. A. Bailey, A. Avni, N. Li, A. K. Matloo, and J. D. Anderson, Plant Physiol. 100:1615-1616, 1992) encoding tobacco 1-aminocyclopropane-l-carboxylic acid synthase as probes, it was established that tobacco contains small gene families for these proteins. Furthermore, RNA blot analyses indicated that transcript levels in leaves for the two ethylene pathway genes were elevated after infection with TMV. The results are discussed in relation to a possible signalling role of ethylene in induced resistance and gene expression for pathogenesis-related proteins.