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- Title
Dual targeting ofMyxococcus xanthusprotoporphyrinogen oxidase into chloroplasts and mitochondria and high level oxyfluorfen resistance.
- Authors
Jung, S.; Lee, Y.; Yang, K.; Lee, S. B.; Jang, S. M.; Ha, S. B.; Back, K.
- Abstract
Much attention has been paid to the signal sequences of eukaryotic protoporphyrinogen oxidases (protoxes); both the organelles targeted by protoxes and the role of protoxes in conferring resistance against protox-inhibiting herbicides, such as oxyfluorfen, have been examined. However, there have been no reports on the translocation of prokaryotic protoxes. This study investigated the targeting ability ofMyxococcus xanthusprotoxin vitroandin vivo. In anin vitrotranslocation assay using a dual import system,M.xanthusprotein was detected in chloroplasts and mitochondria, suggesting that theM.xanthusprotox protein was targeted into both organelles. In order to confirm thein vitrodual targeting ability ofM.xanthus, we used a stable transgenic strategy to investigate dual targetingin vivo. In transgenic rice plants overexpressingM.xanthusprotox,M.xanthusprotox antibody cross-reacted with proteins with predicted molecular masses of 50 kDa from both chloroplasts and mitochondria, and thisin vivotransgene expression corresponded to a prominent increase in chloroplastic and mitochondrial protox activity. Seeds from the transgenic lines M4 and M7 germinated in solid Murashige and Skoog media of up to 500 µmof oxyfluorfen, whereas wild-type seeds did not germinate in 1 µm. After 4-week-old-rice plants were treated with oxyfluorfen for 3 d, lines M4 and M7 exhibited normal growth, whereas the wild-type line was severely bleached and necrotized. The herbicidal resistance is attributed to the insignificant accumulation of photodynamic protoporphyrin IX in cytosol because the high chloroplastic and mitochondrial protox activity in oxyfluorfen-treated transgenic lines, compared with that in oxyfluorfen-treated and untreated wild-type plants, metabolizes protoporphyrinogen IX to chlorophyll and heme. A practical application of the dual targeting ofM.xanthusprotox for obtaining outstanding resistance to peroxidizing herbicides is discussed.
- Subjects
OXIDASES; HERBICIDES; PLANT physiology; PROTEINS; MITOCHONDRIA; HEME
- Publication
Plant, Cell & Environment, 2004, Vol 27, Issue 11, p1436
- ISSN
0140-7791
- Publication type
Article
- DOI
10.1111/j.1365-3040.2004.01247.x