Post-Transcriptional Suppression of ß-1,3-Glucanase Expression in Transgenic Tobacco Plants

Abstract : The Nicotianaplumbaginifolia gnl gene coding for a basic ß-1,3-glucanase has been constitutively expressed in SR1 Nicotiana tabacum plants. Analysis of the progeny of the transgenic plant with the highest level of gnl expression revealed an interesting phenomenon of gene suppression. Plants hemizygous for the T-DNA locus contained high levels of gnl mRNA and protein whereas the expression of the chimeric gnl gene was completely blocked in the homozygous plants. This suppression mechanism occurs at a post-transcriptional level and is under developmental control. In addition, ß-l,3-glucanase isoelectric focusing assays revealed that an endogenous basic isoform was also suppressed in stressed homozygous plants, suggesting that the suppression mechanism operates post-transcriptionally by recognizing specific sequences present in both gnl and the tobacco basic isoform RNA transcripts.