Altered monoterpene composition in transgenic mint following the introduction of 4S-limonene synthase

Genetic transformation of Mentha arvensis and M. x piperita with the neomyc ine phosphotransferase marker gene and a 4S-limonene synthase cDNA from M. spicata led to the regeneration of 47 transformed plants. In these plants, integration of the transgene was checked by PCR and Southern blots. Transcr ipts were detected by RT-PCR and monoterpene profiles were determined by ga s chromatography. Quantitative and qualitative modifications in monoterpene levels were observed in both M. arvensis and M. X piperita transgenic plan ts. Four M. x piperita transgenic plants contained higher levels of total m onoterpenes, whereas monoterpene levels were lower in two M. arvensis trans genic lines. In both M. x piperita and M. arvensis transgenic lines, altere d levels of compounds formed directly from geranyl diphosphate such as cine ole or ocimene and monoterpene end-products such as pulegone or piperitone were observed. These effects were consistent with either over-expression or co-suppression of the 4S-ls gene, depending on the transgenic line. These data demonstrate the feasibility of modifying essential oil content by the introduction of a cDNA encoding an enzyme involved in monoterpene metabolis m. (C) 2001 Editions scientifiques et medicales Elsevier SAS.