Abstract
Xyloglucan (XyG) is the predominant hemicellulose in the primary cell walls of most dicotyledonous plants. Current models of these walls predict that XyG interacts with cellulose microfibrils to provide the wall with the rigidity and strength necessary to maintain cell integrity. Remodeling of this network is required to allow cell elongation and plant growth. In this study, homologs of Arabidopsis thaliana MURUS3 (MUR3), which encodes a XyG-specific galactosyltransferase, were obtained from Brassica rapa (BrMUR3) to Brassica oleracea (BoMUR3). Genetic complementation showed that BrMUR3 and BoMUR3 rescue the phenotypic defects of the mur3-3 mutant. Xyloglucan subunit composition analysis provided evidence that BrMUR3 and BoMUR3 encode a galactosyltransferase, which transfers a galactose residue onto XyG chains. The detection of XXFG and XLFG XyG subunits (restoration of fucosylated side chains) in mur3-3 mutants overexpressing BrMUR3 or BoMUR3 show that MUR3 from Brassica to Arabidopsis are comparable as they add Gal to the third xylosyl residue of the XXXG subunit. Our results provide additional information for functional dissection and evolutionary analysis of MUR3 genes derived from brassicaceous species.
Highlights
Xyloglucan (XyG) is present in the primary cell walls of land plants including gymnosperms, angiosperms, monilophytes, lycophytes, hornworts, mosses and liverworts (Hoffman et al, 2005; Pena et al, 2008; Popper, 2008; Popper & Fry, 2003, 2004)
The MUR3 homologs identified from Camelina sativa, Eutrema salsugineum, Raphanus sativus, B. rapa, B. oleracea and B. napus were mostly closely to Arabidopsis thaliana
Validation of two homologous genes of MUR3 To verify the function of selected MUR3 homologous genes, the constructs containing the coding sequences of R. sativus (XM_018584632.1), B. rapa (XM_009103789.2), B. oleracea (XM_013742723.1), Gossypium hirsutum (XM_016854228.1) and Nicotiana tabacum were transformed into the mur3-3 mutant
Summary
Xyloglucan (XyG) is present in the primary cell walls of land plants including gymnosperms, angiosperms, monilophytes, lycophytes, hornworts, mosses and liverworts (Hoffman et al, 2005; Pena et al, 2008; Popper, 2008; Popper & Fry, 2003, 2004). It has a 1,4-linked β-glucan backbone that is, substituted at O-6 to varying extents with a-Xyl residues (Pauly et al, 2013).
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