Ethylene-Induced Gene Expression of Osmotin-Like Protein, a Neutral Isoform of Tobacco PR-5, is Mediated by the AGCCGCC eft-Sequence

Osmotin-like protein (OLP) is a neutral isoform in the group5 pathogenesis-related (PR) tobacco proteins. The OLP gene,like the basic PR protein genes, is constitutively expressedin tobacco roots and cultured cells. OLP is not naturally presentin intact healthy leaves, but ethylene treatment induces a highaccumulation there. To study the mechanism of OLP gene expressionas induced by ethylene, we cloned the gene from Nicotiana sylvestris,an ancestor of N. tabacum. Sequence analysis showed that ithas no intron and that its promoter region contains two AGCCGCCsequences that are conserved in most basic PR-protein genes.The function of the AGCCGCC sequences in transgenic tobaccoplants that harbor the wild and mutated OLP promoter::GUS fusiongenes was analyzed. Mutation in the AGCCGCC sequences clearlyinhibited the GUS expression induced by ethylene, indicativethat the AGCCGCC sequence(s) is a DNA element(s) responsiveto ethylene. An EREBP2 protein, isolated as one of the proteinsbinding the AGCCGCC sequence of the tobacco rß-1,3-glucanasegene, also was found to bind to the AGCCGCC sequence(s) of OLPgene. These results suggest that the ethylene-induced expressionof OLP is regulated by trans-acting factor(s) common to basicPR-proteins. (Received November 13, 1995; Accepted January 17, 1996)