Potato genetic engineering
Agrobacterium mediated gene transfert on potato
Potato was one of the first crop plants in which plants were successfully regenerated. (An et al, 1986; Shaning and Simpson 1986). Using recombinant gene technology, genes of interest are substitute to oncogenes and some new traits were introduced in potato cultivars ([Table1|http://research.cip.cgiar.org/confluence/display/potatogene/Table+1-+main+new+traits+introduced+in+potato+cultivars]). For almost all transgenic potato plants developed today kanamycin resistance has been used as the selectable marker gene for the selection of transformed events . Diferent transformation protocols have been developped using other selectable markers or potato organs. The following schema presents briefly the steps for agrobacterium mediated potato transformation on leaves and internodes. (CIP protocol).
Somaclonal variation frequency, integration and expression of transgenes are very diferent among transgenic lines. Integration of the transgene may occur in a complete, truncated or arranged manner, as a single or various copies in the genome . The level of expression of a trnsgene often varies among transgenic lines because of the effect of the chromosomal location "position effect' (Peach and velten, 1991) or either co-supression or gene silencing effects (for a review, Matzke et al 1995). By generated a large number of transformed events and by further selection these effects can be circumvented in potato. However, variation in transgene expression, down to silencing have a minor importance in potato crop. The agroinfection system favors low copy number of transgene and clonal propagation will maintain the hemizygousy of transgenic lines with appropriate levels of expression.
Links and references:
An.G., Watson, B.D and Chiang, C.C (1986). Transformation of tobacco, tomato potato and arabidopsis thaliana using a binary Ti vector system. Plant physiology 81: 301-305
Shahin, E.A and Simpson, R.B. (1986) Gene transfer system for potato. HortScience 21:1199-1201
Peach, C., Velten, J., (1991). Transgene expression variability (position effect) of CAT and GUS reporter genes driven by linked divergent T-DNA promoters. Plant Mol Biology 17:49-60
Matzke M.A., Matzke AJM (1995) How and why do plants inactive homologous (trans)-genes? Plant Physiology 107:679-685