Please use this identifier to cite or link to this item: http://hdl.handle.net/2440/23856
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Type: Journal article
Title: Reconstitution of cyanogenesis in barley (Hordeum vulgare L.) and its implications for resistance against the barley powdery mildew fungus
Author: Nielsen, K.
Hrmova, M.
Nielsen, J.
Forslund, K.
Ebert, S.
Olsen, C.
Fincher, G.
Moller, B.
Citation: Planta, 2006; 223(5):1010-1023
Publisher: Springer
Issue Date: 2006
ISSN: 0032-0935
1432-2048
Statement of
Responsibility: 
Kirsten A. Nielsen, Maria Hrmova, Janni Nyvang Nielsen, Karin Forslund, Stefan Ebert, Carl E. Olsen, Geoffrey B. Fincher and Birger Lindberg Møller
Abstract: Barley (Hordeum vulgare L.) produces a leucine-derived cyanogenic β-d-glucoside, epiheterodendrin that accumulates specifically in leaf epidermis. Barley leaves are not cyanogenic, i.e. they do not possess the ability to release hydrogen cyanide, because they lack a cyanide releasing β-d-glucosidase. Cyanogenesis was reconstituted in barley leaf epidermal cells through single cell expression of a cDNA encoding dhurrinase-2, a cyanogenic β-d-glucosidase from sorghum. This resulted in a 35–60% reduction in colonization rate by an obligate parasite Blumeria graminis f. sp. hordei, the causal agent of barley powdery mildew. A database search for barley homologues of dhurrinase-2 identified a (1,4)-β-d-glucan exohydrolase isozyme βII that is located in the starchy endosperm of barley grain. The purified barley (1,4)-β-d-glucan exohydrolase isozyme βII was found to hydrolyze the cyanogenic β-d-glucosides, epiheterodendrin and dhurrin. Molecular modelling of its active site based on the crystal structure of linamarase from white clover, demonstrated that the disposition of the catalytic active amino acid residues was structurally conserved. Epiheterodendrin stimulated appressoria and appressorial hook formation of B. graminis in vitro, suggesting that loss of cyanogenesis in barley leaves has enabled the fungus to utilize the presence of epiheterodendrin to facilitate host recognition and to establish infection.
Keywords: Cyanogenesis
Description: The original publication can be found at www.springerlink.com
RMID: 0020060266
DOI: 10.1007/s00425-005-0158-z
Appears in Collections:Agriculture, Food and Wine publications

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