Lotus japonicus flowers are defended by a cyanogenic β-glucosidase with highly restricted expression to essential reproductive organs

Lotus japonicus flowers are defended by a cyanogenic β-glucosidase with highly restricted... Flowers and leaves of Lotus japonicus contain α-, β-, and γ-hydroxynitrile glucoside (HNG) defense compounds, which are bioactivated by β-glucosidase enzymes (BGDs). The α-HNGs are referred to as cyanogenic glucosides because their hydrolysis upon tissue disruption leads to release of toxic hydrogen cyanide gas, which can deter herbivore feeding. BGD2 and BGD4 are HNG metabolizing BGD enzymes expressed in leaves. Only BGD2 is able to hydrolyse the α-HNGs. Loss of function mutants of BGD2 are acyanogenic in leaves but fully retain cyanogenesis in flowers pointing to the existence of an alternative cyanogenic BGD in flowers. This enzyme, named BGD3, is identified and characterized in this study. Whereas all floral tissues contain α-HNGs, only those tissues in which BGD3 is expressed, the keel and the enclosed reproductive organs, are cyanogenic. Biochemical analysis, active site architecture molecular modelling, and the observation that L. japonicus accessions lacking cyanogenic flowers contain a non-functional BGD3 gene, all support the key role of BGD3 in floral cyanogenesis. The nectar of L. japonicus flowers was also found to contain HNGs and additionally their diglycosides. The observed specialisation in HNG based defence in L. japonicus flowers is discussed in the context of balancing the attraction of pollinators with the protection of reproductive structures against herbivores. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Plant Molecular Biology Springer Journals

Lotus japonicus flowers are defended by a cyanogenic β-glucosidase with highly restricted expression to essential reproductive organs

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Publisher
Springer Journals
Copyright
Copyright © 2015 by Springer Science+Business Media Dordrecht
Subject
Life Sciences; Plant Sciences; Biochemistry, general; Plant Pathology
ISSN
0167-4412
eISSN
1573-5028
D.O.I.
10.1007/s11103-015-0348-4
Publisher site
See Article on Publisher Site

Abstract

Flowers and leaves of Lotus japonicus contain α-, β-, and γ-hydroxynitrile glucoside (HNG) defense compounds, which are bioactivated by β-glucosidase enzymes (BGDs). The α-HNGs are referred to as cyanogenic glucosides because their hydrolysis upon tissue disruption leads to release of toxic hydrogen cyanide gas, which can deter herbivore feeding. BGD2 and BGD4 are HNG metabolizing BGD enzymes expressed in leaves. Only BGD2 is able to hydrolyse the α-HNGs. Loss of function mutants of BGD2 are acyanogenic in leaves but fully retain cyanogenesis in flowers pointing to the existence of an alternative cyanogenic BGD in flowers. This enzyme, named BGD3, is identified and characterized in this study. Whereas all floral tissues contain α-HNGs, only those tissues in which BGD3 is expressed, the keel and the enclosed reproductive organs, are cyanogenic. Biochemical analysis, active site architecture molecular modelling, and the observation that L. japonicus accessions lacking cyanogenic flowers contain a non-functional BGD3 gene, all support the key role of BGD3 in floral cyanogenesis. The nectar of L. japonicus flowers was also found to contain HNGs and additionally their diglycosides. The observed specialisation in HNG based defence in L. japonicus flowers is discussed in the context of balancing the attraction of pollinators with the protection of reproductive structures against herbivores.

Journal

Plant Molecular BiologySpringer Journals

Published: Aug 7, 2015

References

  • Ecological costs and benefits of defenses in nectar
    Adler, LS; Irwin, RE
  • Reliance on pollinators predicts defensive chemistry across tobacco species
    Adler, LS; Seifert, MG; Wink, M; Morse, GE
  • A combined biochemical screen and TILLING approach identifies mutations in Sorghum bicolor L. Moench resulting in acyanogenic forage production
    Blomstedt, CK; Gleadow, RM; O’Donnell, N; Naur, P; Jensen, K; Laursen, T; Olsen, CE; Stuart, P; Hamil, JD; Møller, BL; Neale, AD

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