21 December 2005

Source: CropBiotech Update

Marker genes are used in genetic engineering to check if a plant has been successfully transformed with a desired trait. Such marker genes may allow a plant cell to be resistant to a certain antibiotic, or to express a certain color, or produce a certain protein. Some concerns on the persistence of such marker genes have been expressed, however, prompting scientists to turn to other possible markers, or alternative methods for selecting successfully transformed cells.

Some markers are also suited only to certain plants, and it can be difficult to find markers which could aid in engineering better crop species. One such plant is durum wheat, and A. Gadaletam of the University of Bari, Italy and colleagues use it as their subject in their study. In an article in the latest issue of the Journal of Cereal Science, researchers report “Phosphomannose isomerase, pmi, as a selectable marker gene for durum wheat transformation.”

Scientists compared the selection efficiency of two genes: bar, from Streptomyces hygroscopicus, which allows cells to be resistant to the herbicide bialaphos; and phosphomannose isomerase (pmi) from Escherichia coli, which allows transformed cells to be selected by a color assay. By using these genes as markers on durum wheat cv. Svevo, they found that selection efficiency was higher for plants with pmi (90.1%) than with bar (26.4%). The enzyme for which pmi codes is, moreover, common in nature, and present in soybean and several other legumes.

Subscribers to the Journal of Cereal Science can read the article at http://dx.doi.org/10.1016/j.jcs.2005.06.004.