Abstract
β-Galactoglucomannan (β-GGM) is a primary cell wall polysaccharide in rosids and asterids. The β-GGM polymer has a backbone of repeating β-(1,4)-glucosyl and mannosyl residues, usually with mono-α-(1,6)-galactosyl substitution or β-(1,2)-galactosyl α-galactosyl disaccharide side chains on the mannosyl residues. Mannan β-galactosyltransferases (MBGTs) are therefore required for β-GGM synthesis. The single MBGT identified so far, AtMBGT1, lies in glycosyltransferase family 47A subclade VII and was identified in Arabidopsis. However, despite the presence of β-GGM, an orthologous gene is absent in tomato (Solanum lycopersicum), a model asterid. In this study, we screened candidate MBGT genes from the tomato genome, functionally tested the activities of encoded proteins and identified the tomato MBGT (SlMBGT1) in GT47A-III. Interestingly therefore, AtMBGT1 and SlMBGT1 are located in different GT47A subclades. Furthermore, phylogenetic and glucomannan structural analysis from different species raised the possibility that various asterids possess conserved MBGTs in an asterid-specific subclade of GT47A-III, indicating that MBGT activity has been acquired convergently among asterids and rosids. The present study highlights the promiscuous emergence of donor and acceptor preference in GT47A enzymes. The independent acquisition of the activity also suggests an adaptive advantage for eudicots to acquire β-GGM β-galactosylation and hence also suggests that the disaccharide side chains are important for β-GGM function.
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Claims 6
Claim · model-written summary
Tomato MBGT activity was assigned to SlMBGT1 in GT47A-III.
- Taxon
- tomato
Solanum lycopersicume0 - Gene
- SlMBGT1e0
- Outcome
- MBGTe0
- Qualifier
- GT47A-IIIe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“identified the tomato MBGT (SlMBGT1) in GT47A-III”
Claim · model-written summary
AtMBGT1 and SlMBGT1 occur in different GT47A subclades.
- Taxon
- Arabidopsis
Arabidopsist0 - Gene
- AtMBGT1 and SlMBGT1e0
- Outcome
- different GT47A subcladese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“AtMBGT1 and SlMBGT1 are located in different GT47A subclades”
t0“identified in Arabidopsis”
Claim · model-written summary
Phylogenetic and structural analyses suggested conserved MBGTs in an asterid-specific GT47A-III subclade.
Not reportedDirection
Verbatim
e0“various asterids possess conserved MBGTs in an asterid-specific subclade of GT47A-III”
Claim · model-written summary
The authors inferred convergent acquisition of MBGT activity among asterids and rosids.
- Outcome
- MBGT activity has been acquired convergentlye0
Verbatim
e0“MBGT activity has been acquired convergently among asterids and rosids”
Claim · model-written summary
Independent acquisition of MBGT activity was interpreted to imply adaptive value for beta-GGM galactosylation.
- Taxon
- eudicotseudicotyledonse0
- Outcome
- adaptive advantagee0
- Qualifier
- β-GGM β-galactosylatione0
Verbatim
e0“The independent acquisition of the activity also suggests an adaptive advantage for eudicots to acquire β-GGM β-galactosylation”
Claim · model-written summary
Disaccharide side chains were suggested to matter for beta-GGM function.
- Taxon
- eudicotseudicotyledonst0
- Outcome
- β-GGM functione0
- Qualifier
- disaccharide side chainse0
Verbatim
e0“the disaccharide side chains are important for β-GGM function”
t0“adaptive advantage for eudicots”