Journal
PLANT JOURNAL
Volume 79, Issue 2, Pages 299-311Publisher
WILEY
DOI: 10.1111/tpj.12561
Keywords
Lotus japonicus; beta-glucosidase; enzyme evolution; cyanogenesis; hydroxynitrile glucosides; rhodiocyanosides; Lotus burttii; Lotus krylovii; Lotus filicaulis; Lotus corniculatus
Categories
Funding
- Danish National Research Foundation (Danmarks Grundforskningsfond)
- Danish Council for Independent Research - Natural Sciences
- VILLUM Research Center 'Plant Plasticity'
- Danish Council for Independent Research - Technology and Production Sciences
- Biotechnology and Biological Sciences Research Council [BB/I025891/1]
- Biotechnology and Biological Sciences Research Council [BBS/E/J/00000150, BB/I025891/1] Funding Source: researchfish
- Villum Fonden [00007523] Funding Source: researchfish
- BBSRC [BB/I025891/1] Funding Source: UKRI
Ask authors/readers for more resources
Lotus japonicus, like several other legumes, biosynthesizes the cyanogenic alpha-hydroxynitrile glucosides lot-australin and linamarin. Upon tissue disruption these compounds are hydrolysed by a specific beta-glucosidase, resulting in the release of hydrogen cyanide. Lotus japonicus also produces the non-cyanogenic gamma- and beta-hydroxynitrile glucosides rhodiocyanoside A and D using a biosynthetic pathway that branches off from lotaustralin biosynthesis. We previously established that BGD2 is the only beta-glucosidase responsible for cyanogenesis in leaves. Here we show that the paralogous BGD4 has the dominant physiological role in rhodiocyanoside degradation. Structural modelling, site-directed mutagenesis and activity assays establish that a glycine residue (G211) in the aglycone binding site of BGD2 is essential for its ability to hydrolyse the endogenous cyanogenic glucosides. The corresponding valine (V211) in BGD4 narrows the active site pocket, resulting in the exclusion of non-flat substrates such as lotaustralin and linamarin, but not of the more planar rhodiocyanosides. Rhodiocyanosides and the BGD4 gene only occur in L. japonicus and a few closely related species associated with the Lotus corniculatus clade within the Lotus genus. This suggests the evolutionary scenario that substrate specialization for rhodiocyanosides evolved from a promiscuous activity of a progenitor cyanogenic beta-glucosidase, resembling BGD2, and required no more than a single amino acid substitution.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available