The bifurcation of the cyanogenic glucoside and glucosinolate biosynthetic pathways

TY - JOUR

T1 - The bifurcation of the cyanogenic glucoside and glucosinolate biosynthetic pathways

AU - Clausen, Mette

AU - Kannangara, Rubini Maya

AU - Olsen, Carl Erik

AU - Blomstedt, Cecilia K.

AU - Gleadow, Roslyn M.

AU - Jørgensen, Kirsten

AU - Bak, Søren

AU - Motawie, Mohammed Saddik

AU - Møller, Birger Lindberg

PY - 2015/11

Y1 - 2015/11

N2 - The biosynthetic pathway for the cyanogenic glucoside dhurrin in sorghum has previously been shown to involve the sequential production of (E)- and (Z)-p-hydroxyphenylacetaldoxime. In this study we used microsomes prepared from wild-type and mutant sorghum or transiently transformed Nicotiana benthamiana to demonstrate that CYP79A1 catalyzes conversion of tyrosine to (E)-p-hydroxyphenylacetaldoxime whereas CYP71E1 catalyzes conversion of (E)-p-hydroxyphenylacetaldoxime into the corresponding geometrical Z-isomer as required for its dehydration into a nitrile, the next intermediate in cyanogenic glucoside synthesis. Glucosinolate biosynthesis is also initiated by the action of a CYP79 family enzyme, but the next enzyme involved belongs to the CYP83 family. We demonstrate that CYP83B1 from Arabidopsis thaliana cannot convert the (E)-p-hydroxyphenylacetaldoxime to the (Z)-isomer, which blocks the route towards cyanogenic glucoside synthesis. Instead CYP83B1 catalyzes the conversion of the (E)-p-hydroxyphenylacetaldoxime into an S-alkyl-thiohydroximate with retention of the configuration of the E-oxime intermediate in the final glucosinolate core structure. Numerous microbial plant pathogens are able to detoxify Z-oximes but not E-oximes. The CYP79-derived E-oximes may play an important role in plant defense. Significance Statement Cyanogenic glucosides and glucosinolates serve multiple functions including plant defense. Here we elucidate the biochemical basis for bifurcation of their biosynthetic pathways and suggest that switching between these biosynthetic pathways gives flexibility against specific fungal and insect attackers.

AB - The biosynthetic pathway for the cyanogenic glucoside dhurrin in sorghum has previously been shown to involve the sequential production of (E)- and (Z)-p-hydroxyphenylacetaldoxime. In this study we used microsomes prepared from wild-type and mutant sorghum or transiently transformed Nicotiana benthamiana to demonstrate that CYP79A1 catalyzes conversion of tyrosine to (E)-p-hydroxyphenylacetaldoxime whereas CYP71E1 catalyzes conversion of (E)-p-hydroxyphenylacetaldoxime into the corresponding geometrical Z-isomer as required for its dehydration into a nitrile, the next intermediate in cyanogenic glucoside synthesis. Glucosinolate biosynthesis is also initiated by the action of a CYP79 family enzyme, but the next enzyme involved belongs to the CYP83 family. We demonstrate that CYP83B1 from Arabidopsis thaliana cannot convert the (E)-p-hydroxyphenylacetaldoxime to the (Z)-isomer, which blocks the route towards cyanogenic glucoside synthesis. Instead CYP83B1 catalyzes the conversion of the (E)-p-hydroxyphenylacetaldoxime into an S-alkyl-thiohydroximate with retention of the configuration of the E-oxime intermediate in the final glucosinolate core structure. Numerous microbial plant pathogens are able to detoxify Z-oximes but not E-oximes. The CYP79-derived E-oximes may play an important role in plant defense. Significance Statement Cyanogenic glucosides and glucosinolates serve multiple functions including plant defense. Here we elucidate the biochemical basis for bifurcation of their biosynthetic pathways and suggest that switching between these biosynthetic pathways gives flexibility against specific fungal and insect attackers.

U2 - 10.1111/tpj.13023

DO - 10.1111/tpj.13023

M3 - Journal article

C2 - 26361733

SN - 0960-7412

VL - 84

SP - 558

EP - 573

JO - Plant Journal

JF - Plant Journal

IS - 3

ER -