    1.3.5.5 | fluridone |
arginine304 present in the wild-type Hydrilla verticillata phytoene desaturase is substituted with all 19 other natural amino acids. In vitro the threonine (Thr), cysteine (Cys), alanine (Ala) and glutamine (Gln) mutations impart the highest resistance to fluridone. The three natural mutations [Cys, serine (Ser), histidine (His)] and the wild-type phytoene desaturase protein are tested in vitro against seven inhibitors of phytoene desaturase representing several classes of herbicides. These mutations confer cross-resistance to norflurazon and overall negative cross-resistance to beflubutamid, picolinafen and diflufenican. The Thr304 Hydrilla pds mutant is an excellent marker for the selection of transgenic plants. Seedlings harbouring Thr304 pds have a maximum resistance to sensitivity (R/S) ratio of 57 and 14 times higher than that of the wild-type for treatments with norflurazon and fluridone, respectively. These plants exhibit normal growth and development, even after long-term exposure to herbicide. As Thr304 pds is of plant origin, it could become more acceptable than other selectable markers for use in genetically modified food |
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