title: Resistance to protoporphyrinogen oxidase-inhibiting compound S23142 from overproduction of mitochondrial protoporphyrinogen oxidase by gene amplification in photomixotrophic tobacco cells.
abstract: Tobacco YZI-IS cells exhibit a 150-fold greater resistance to the protoporphyrinogen oxidase (Protox)-inhibiting compound, S23142, from wild-type tobacco cells. To investigate the mechanism for this S23142 resistance, the protein level, enzymatic activity, and sensitivity to S23142 in two Protox isoenzymes (plastidal and mitochondrial forms) were examined. The level of mitochondrial Protox protein was greater, and its activity 5-times higher, in YZI-IS cells than in wild-type cells. Furthermore, the apparent IC50 value of S23142 was about 20 nM, which is 20-fold higher than that observed in wild-type cells. In contrast, no differences were found in the plastidal Protox protein level, activity or its inhibition by S23142 between YZI-1S and wild-type cells. A southern blot analysis revealed that the mitochondrial Protox gene had been significantly amplified in the YZI-1S cells. These results suggest that the S23142 resistance of YZI-1S cells was due to the overproduction of mitochondrial Protox by gene amplification.
authors.affiliation: Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara, Japan.
authors.forename: Naohide
authors.initials: N
authors.lastname: Watanabe
authors.forename: Seiji
authors.initials: S
authors.lastname: Takayama
authors.forename: Shigeo
authors.initials: S
authors.lastname: Yoshida
authors.forename: Akira
authors.initials: A
authors.lastname: Isogai
authors.forename: Fang-Sik
authors.initials: FS
authors.lastname: Che
mesh_terms: D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance; D005784:Gene Amplification / Q000187:drug effects*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D007527:Isoenzymes / Q000096:biosynthesis / Q000235:genetics; D016015:Logistic Models; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D010088:Oxidoreductases / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D044925:Oxidoreductases Acting on CH-CH Group Donors; D010797:Phthalimides / Q000494:pharmacology*; D050768:Protoporphyrinogen Oxidase; D014026:Nicotiana / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology* / Q000235:genetics
chemical_list: D007527:Isoenzymes; C474812:N-(4-chloro-2-fluoro-5-propargyloxy)phenyl-2,4,5,6-tetrahydrophthalimide; D010797:Phthalimides; D010088:Oxidoreductases; D044925:Oxidoreductases Acting on CH-CH Group Donors; D050768:Protoporphyrinogen Oxidase