Biosynthesis of camalexin from tryptophan pathway intermediates in cell-suspension cultures of Arabidopsis.
Camalexin (3-thiazol-2'-yl-indole) is the principal phytoalexin that accumulates in Arabidopsis after infection by fungi or bacteria. Camalexin accumulation was detectable in Arabidopsis cell-suspension cultures 3 to 5 h after inoculation with Cochliobolus carbonum (Race 1), and then increased rapidly from 7 to 24 h after inoculation. Levels of radioactivity incorporated into camalexin during a 1.5-h pulse labeling with [14C]anthranilate also increased with time after fungal inoculation. The levels of radioactive incorporation into camalexin increased rapidly between 7 and 18 h after inoculation, and then decreased along with camalexin accumulation. Relatively low levels of radioactivity from [14C]anthranilate incorporated into camalexin in the noninoculated controls. Autoradiographic analysis of the accumulation of chloroform-extractable metabolites labeled with [14C]anthranilate revealed a transient increase in the incorporation of radioactivity into indole in fungus-inoculated Arabidopsis cell cultures. The time-course measurement of radioactive incorporation into camalexin during a 1.5-h pulse labeling with [14C]indole was similar to that with [14C]anthranilate. These data suggest that indole destined for camalexin synthesis is produced by a separate enzymatic reaction that does not involve tryptophan synthase.
Zook
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Department of Botany and Plant Pathology, Michigan State University, East Lansing, Michigan 48824, USA. hammerS1@pilot.msu.edu
D017360:Arabidopsis / Q000166:cytology / Q000378:metabolism* / Q000382:microbiology; D001203:Ascomycota / Q000472:pathogenicity; D002478:Cells, Cultured; D007211:Indoles / Q000378:metabolism*; D007700:Kinetics; D010935:Plant Diseases / Q000382:microbiology; D013844:Thiazoles / Q000378:metabolism*; D014364:Tryptophan / Q000378:metabolism*; D062367:ortho-Aminobenzoates / Q000378:metabolism; D000094162:Phytoalexins
D007211:Indoles; D013844:Thiazoles; D014364:Tryptophan; D062367:ortho-Aminobenzoates; C102405:camalexin; D000094162:Phytoalexins; C031385:anthranilic acid; C030374:indole