PLANT PHYSIOLOGY , Vol 103, Issue 3 911-917, Copyright © 1993 by American Society of Plant Biologists
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MOLECULAR BIOLOGY AND GENE REGULATION |
A Serine-to-Threonine Substitution in the Triazine Herbicide-Binding Protein in Potato Cells Results in Atrazine Resistance without Impairing Productivity
R. J. Smeda, P. M. Hasegawa, P. B. Goldsbrough, N. K. Singh and S. C. Weller
Department of Horticulture, Purdue University, West Lafayette, Indiana 47907-1165
A mutation of the psbA gene was identified in photoautotrophic potato
(Solanum tuberosum L. cv Superior x U.S. Department of Agriculture line
66-142) cells selected for resistance to
6-chloro-N-ethyl-N[prime]-(1-methylethyl)-1,3,5-triazine-2,4-diamine
(atrazine). Photoaffinity labeling with
6-azido-N-ethyl-N[prime]-(1-methylethyl)-1,3,5-triazine-2,4-diamine
detected a thylakoid membrane protein with a Mr of 32,000 in susceptible,
but not in resistant, cells. This protein was identified as the secondary
quinone acceptor of photosystem II (QB) protein. Atrazine resistance in
selected cells was attributable to a mutation from AGT (serine) to ACT
(threonine) in codon 264 of the psbA gene that encodes the QB protein.
Although the mutant cells exhibited extreme levels of resistance to
atrazine, no concomitant reductions in photosynthetic electron transport or
cell growth rates compared to the unselected cells were detected. This is
in contrast with the losses in productivity observed in atrazine-resistant
mutants that contain a glycine-264 alteration.
