The commercial herbicide Atrax R (triazine) prevents electrons from passing thro
ID: 59026 • Letter: T
Question
The commercial herbicide AtraxR (triazine) prevents electrons from passing through the electron transport chain from plastiquinone to cytochrome b6f. For years, triazine was widely used for routine weed control, but recently several weed species were reported to be resistant to triazine. Electron transport is essential for photosynthesis, so the weeds cannot just eliminate the pathway and gain resistance. How then might a weed become resistant to triazine? (Hint: First decide what triazine would have to do to block electron transport. Then ask, how could a plant prevent triazine from having that effect?)
Explanation / Answer
TRiazine binds to the Qb site on the D1 protein to prevent plastoquinone from binding to cytochrome b6f.
The weeds can gain resistance by altering the sequence of the Qb site so that triazine cannot bind to the Qb site. Hence, triazine becomes useless and the weeds gain resistance.