Expression of a chimeric stilbene synthase gene in transgenic wheat lines
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A chimeric stilbene synthase (sts)‐gene was transferred into wheat. Stilbene synthases play a role in the defence against fungal diseases in some plant species (e.g. groundnut or grapevine) by producing stilbene‐type phytoalexins like resveratrol. Resveratrol is also claimed to have positive effects to human health. Embryogenic scutellar calli derived from immature embryos of the two commercial German spring wheat cultivars ‘Combi’ and ‘Hanno’ were used as target tissue for co‐transformation by microprojectile delivery. The selectable marker/reporter gene constructs contained the bar‐gene either driven by the ubiquitin‐promoter from maize (pAHC 25, also containing the uidA‐gene driven by the ubiquitin‐promoter), or by the actin‐promoter (pDM 302) from rice. The co‐transferred plasmid pStil 2 consisted of a grapevine sts‐coding region driven by the ubiquitin promoter. Eight transgenic ‘Combi’ and one ‘Hanno’ TO‐plant were obtained and, except one ‘Combi’ TO‐plant, found to be co‐transformants due to the integration of both the sts‐gene and the selectable marker or reporter genes. Expression of the sts‐gene was proven by RT‐PCR, and, for the first time, by detection of the stilbene synthase product resveratrol by HPLC and mass spectrometry. The sts‐gene was expressed in four of the seven transgenic ‘Combi’ T_o‐plants. Two of the respective T1‐progenies segregated in a Mendelian manner were still expressing the gene. Investigations into methylation of the sts‐gene showed that in three non‐expressing progenies inactivation was paralleled by methylation.
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