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Toxicity symptoms caused by high expression of Tet repressor in tomato (Lycopersicon esculentum Mill. L.) are alleviated by tetracycline

Corlett, J.E., Myatt, S.C., Thompson, A.J.
Plant, cell and environment 1996 v.19 no.4 pp. 447-454
Solanum lycopersicum var. lycopersicum, gene transfer, structural genes, DNA-binding proteins, Gram-negative bacteria, transgenic plants, genetic transformation, gene expression, messenger RNA, phytotoxicity, dry matter accumulation, roots, shoots, chlorophyll, photosynthesis, tetracycline
As a first step towards transferring a tetracycline (Tc)-inducible gene expression system to tomato, we have transformed tomato plants with the Tn10-encoded tet repressor gene (tetR). Homozygous transformed plants with high expression of tetR mRNA show a deleterious phenotype, having reduced shoot dry weights and leaf chlorophyll content, an even more marked reduction in root dry weight and leaf size, and altered photosynthetic physiology. It appears that TetR protein exerts its toxicity only when expressed beyond a threshold level and by interacting with a process that is non-limiting under slow growth conditions. The deleterious phenotype was almost completely reversed by the application of 1 mg dm-3 Tc to plants grown in sand. The possibility is discussed that TetR causes these symptoms by binding to a specific DNA sequence functioning as a Tet operator. The effect of Tc on growth and physiology in wild-type plants grown in sand or rockwool is described. Tc at 0.1 mg cm-3 had no effect. Tc at 1 mg dm-3 caused a small reduction in root growth, while 5 and 20mg dm-3 Tc caused large reductions in growth and photosynthetic parameters.