Optimisation of transgene action at the post-transcriptional level: high quality parthenocarpic fruits in industrial tomatoes

• Main Authors: Defez Roberto, Camerini Serena, Rotino Giuseppe L, Pandolfini Tiziana, Spena Angelo
• Format: Article
• Language: English
• Published: BMC 2002-01-01
• Series: BMC Biotechnology
• Online Access: http://www.biomedcentral.com/1472-6750/2/1

<p>Abstract</p> <p>Background</p> <p>Genetic engineering of parthenocarpy confers to horticultural plants the ability to produce fruits under environmental conditions that curtail fruit productivity and quality. The <it>DefH9-iaaM</it> transgene, whose predicted action is to confer auxin synthesis specifically in the placenta, ovules and derived tissues, has been shown to confer parthenocarpy to several plant species (tobacco, eggplant, tomato) and varieties.</p> <p>Results</p> <p>UC82 tomato plants, a typical cultivar used by the processing industry, transgenic for the <it>DefH9-iaaM</it> gene produce parthenocarpic fruits that are malformed. UC82 plants transgenic for the <it>DefH9-RI-iaaM,</it> a <it>DefH9-iaaM</it> derivative gene modified in its 5'ULR by replacing 53 nucleotides immediately upstream of the AUG initiation codon with an 87 nucleotides-long sequence derived from the <it>rolA</it> intron sequence, produce parthenocarpic fruits of high quality. In an <it>in vitro</it> translation system, the <it>iaaM</it> mRNA, modified in its 5'ULR is translated 3–4 times less efficiently than the original transcript. An optimal expressivity of parthenocarpy correlates with a reduced transgene mRNA steady state level in <it>DefH9-RI-iaaM</it> flower buds in comparison to <it>DefH9-iaaM</it> flower buds. Consistent with the known function of the <it>iaaM</it> gene, flower buds transgenic for the <it>DefH9-RI-iaaM</it> gene contain ten times more IAA than control untransformed flower buds, but five times less than <it>DefH9-iaaM</it> flower buds.</p> <p>Conclusions</p> <p>By using an auxin biosynthesis transgene downregulated at the post-transcriptional level, an optimal expressivity of parthenocarpy has been achieved in a genetic background not suitable for the original transgene. Thus, the method allows the generation of a wider range of expressivity of the desired trait in transgenic plants.</p>