ANALYSIS OF ARABIDOPSIS CDNA THAT SHOWS HOMOLOGY TO THE TOMATO E8 CDNA

The negative regulatory protein of ethylene synthesis in ripening toma to fruit, E8, is structurally related to the enzyme that catalyzes the last step in ethylene synthesis,1-aminocyclopropane-1-carboxylate (AC C) oxidase, and to a large family of 2-oxoglutarate-dependent dioxygen ases (2-ODD). A cDNA with structural homology to the tomato E8 was iso lated from a cDNA library of Arabidopsis thaliana. Sequence analysis s howed that this cDNA, 2A6, encodes a protein of 361 amino acids. South ern blot analysis indicated that the corresponding gene is unique in t he Arabidopsis genome. The level of the 2A6 transcript was not increas ed by ethylene in siliques of Arabidopsis, as was E8 in tomato fruits, and was also expressed in etiolated seedlings, leaves, stems and flow ers. The 2A6 protein shows three domains that are highly conserved amo ng E8, ACC oxidases, and 2-ODDs.