Dhurrin synthesis in sorghum is regulated at the transcriptional level and induced by nitrogen fertilization in older plants.
The content of the cyanogenic glucoside dhurrin in sorghum (Sorghum bicolor L. Moench) varies depending on plant age and growth conditions. The cyanide potential is highest shortly after onset of germination. At this stage, nitrogen application has no effect on dhurrin content, whereas in older plants, nitrogen application induces an increase. At all stages, the content of dhurrin correlates well with the activity of the two biosynthetic enzymes, CYP79A1 and CYP71E1, and with the protein and mRNA level for the two enzymes. During development, the activity of CYP79A1 is lower than the activity of CYP71E1, suggesting that CYP79A1 catalyzes the rate-limiting step in dhurrin synthesis as has previously been shown using etiolated seedlings. The site of dhurrin synthesis shifts from leaves to stem during plant development. In combination, the results demonstrate that dhurrin content in sorghum is largely determined by transcriptional regulation of the biosynthetic enzymes CYP79A1 and CYP71E1.
Plant Biochemistry Laboratory, Department of Plant Biology, and Center for Molecular Plant Physiology, Royal Veterinary and Agricultural University, 40 Thorvaldsensvej, DK-1871 Frederiksberg C, Copenhagen, Denmark.
Peter Kamp
PK
Busk
Birger Lindberg
BL
Møller
D003486:Cyanides / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism; D005308:Fertilizers; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D006027:Glycosides / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000378:metabolism; D009566:Nitrates / Q000494:pharmacology; D009570:Nitriles / Q000378:metabolism*; D009584:Nitrogen / Q000494:pharmacology*; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D018547:Plant Stems / Q000235:genetics / Q000378:metabolism; D006109:Poaceae / Q000235:genetics / Q000378:metabolism*; D011189:Potassium Chloride / Q000494:pharmacology; D017680:Potassium Compounds / Q000494:pharmacology; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D013997:Time Factors; D014158:Transcription, Genetic / Q000187:drug effects
D003486:Cyanides; D005308:Fertilizers; D006027:Glycosides; D009566:Nitrates; D009570:Nitriles; D017680:Potassium Compounds; D012333:RNA, Messenger; C007173:cyanogenic glycosides; D011189:Potassium Chloride; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; C089817:cytochrome P450TYR; C110889:cytochrome P-450 CYP71E1 (sorghum); D009584:Nitrogen; C011220:dhurrin; C023844:potassium nitrate