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Stratilová B, Šesták S, Mravec J, Garajová S, Pakanová Z, Vadinová K, Kučerová D, Kozmon S, Schwerdt JG, Shirley N, Stratilová E, Hrmova M. Another building block in the plant cell wall: Barley xyloglucan xyloglucosyl transferases link covalently xyloglucan and anionic oligosaccharides derived from pectin. Plant J 2020; 104:752-767. [PMID: 32799357 DOI: 10.1111/tpj.14964] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Revised: 07/17/2020] [Accepted: 07/29/2020] [Indexed: 05/27/2023]
Abstract
We report on the homo- and hetero-transglycosylation activities of the HvXET3 and HvXET4 xyloglucan xyloglucosyl transferases (XET; EC 2.4.1.207) from barley (Hordeum vulgare L.), and the visualisation of these activities in young barley roots using Alexa Fluor 488-labelled oligosaccharides. We discover that these isozymes catalyse the transglycosylation reactions with the chemically defined donor and acceptor substrates, specifically with the xyloglucan donor and the penta-galacturonide [α(1-4)GalAp]5 acceptor - the homogalacturonan (pectin) fragment. This activity is supported by 3D molecular models of HvXET3 and HvXET4 with the docked XXXG donor and [α(1-4)GalAp]5 acceptor substrates at the -4 to +5 subsites in the active sites. Comparative sequence analyses of barley isoforms and seed-localised TmXET6.3 from nasturtium (Tropaeolum majus L.) permitted the engineering of mutants of TmXET6.3 that could catalyse the hetero-transglycosylation reaction with the xyloglucan/[α(1-4)GalAp]5 substrate pair, while wild-type TmXET6.3 lacked this activity. Expression data obtained by real-time quantitative polymerase chain reaction of HvXET transcripts and a clustered heatmap of expression profiles of the gene family revealed that HvXET3 and HvXET6 co-expressed but did not share the monophyletic origin. Conversely, HvXET3 and HvXET4 shared this relationship, when we examined the evolutionary history of 419 glycoside hydrolase 16 family members, spanning monocots, eudicots and a basal Angiosperm. The discovered hetero-transglycosylation activity in HvXET3 and HvXET4 with the xyloglucan/[α(1-4)GalAp]5 substrate pair is discussed against the background of roles of xyloglucan-pectin heteropolymers and how they may participate in spatial patterns of cell wall formation and re-modelling, and affect the structural features of walls.
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Affiliation(s)
- Barbora Stratilová
- Institute of Chemistry, Centre for Glycomics, Slovak Academy of Sciences, Dúbravská cesta 9, Bratislava, SK-84538, Slovakia
- Faculty of Natural Sciences, Department of Physical and Theoretical Chemistry, Comenius University, Mlynská dolina, Bratislava, SK-842 15, Slovakia
| | - Sergej Šesták
- Institute of Chemistry, Centre for Glycomics, Slovak Academy of Sciences, Dúbravská cesta 9, Bratislava, SK-84538, Slovakia
| | - Jozef Mravec
- Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, Frederiksberg-C, 1871, Denmark
| | - Soňa Garajová
- Institute of Chemistry, Centre for Glycomics, Slovak Academy of Sciences, Dúbravská cesta 9, Bratislava, SK-84538, Slovakia
- School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, SA, 5064, Australia
| | - Zuzana Pakanová
- Institute of Chemistry, Centre for Glycomics, Slovak Academy of Sciences, Dúbravská cesta 9, Bratislava, SK-84538, Slovakia
| | - Kristína Vadinová
- Institute of Chemistry, Centre for Glycomics, Slovak Academy of Sciences, Dúbravská cesta 9, Bratislava, SK-84538, Slovakia
| | - Danica Kučerová
- Institute of Chemistry, Centre for Glycomics, Slovak Academy of Sciences, Dúbravská cesta 9, Bratislava, SK-84538, Slovakia
| | - Stanislav Kozmon
- Institute of Chemistry, Centre for Glycomics, Slovak Academy of Sciences, Dúbravská cesta 9, Bratislava, SK-84538, Slovakia
| | - Julian G Schwerdt
- School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, SA, 5064, Australia
| | - Neil Shirley
- School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, SA, 5064, Australia
| | - Eva Stratilová
- Institute of Chemistry, Centre for Glycomics, Slovak Academy of Sciences, Dúbravská cesta 9, Bratislava, SK-84538, Slovakia
| | - Maria Hrmova
- School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, SA, 5064, Australia
- School of Life Sciences, Huaiyin Normal University, Huai'an, 223300, China
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