Mutant Name: pnt1
| Gene Name | PNT1 |
| Protein Name | mannosyltransferase PIG-M |
| Mutagen | EMS |
| Category | forward genetics |
| Organism | Arabidopsis thaliana |
| Ecotype | Lb |
| Donor | |
| General Description |
1.Mutants are seedling lethal,but able to proliferate as callus. Mutant embryos exhibit a radially swollen phenotype and delayed morphogenesis and abnomal cell divisions. 2.pnt1 mutant cell walls showed decreased crystalline cellulose, increased pectins, and irregular and ectopic deposition of pectins, xyloglucans, and callose. 3.The PNT1 gene encodes the Arabidopsis thaliana homolog of mammalian PIG-M, an endoplasmic reticulum localized mannosyltransferase that is required for synthesis of the glycosylphosphatidylinositol (GPI) anchor. All five pnt mutants showed strongly reduced accumulation of GPI-anchored proteins, suggesting that they all have defects in GPI anchor synthesis. |
| Organ Specificity | PNT1 mRNA was found to be present at low levels in roots, hypocotyls, leaves, and stems and at higher levels in the inflorescence meristem. |
| Impact on Wall |
1.Ectopic Accumulation of Xyloglucan, Pectin, and Callose in pnt1 Embryos and Ectopic Callose in pnt1 Callus. 2.In pnt1 embryos, JIM5 epitopes are more abundant than in the wild type and are not confined to the middle lamella and three cell junctions. 3.light microscopic analysis revealed that the deposition pattern of cell wall polymers was aberrant in pnt1 embryos. mutant embryo cell walls contain increased amounts of cell wall material that are found in large patches appressed to the primary wall. This strongly suggests that pnt1 mutants are impaired in integrating secreted polysaccharides into a functional wall. |
| Impact on Sugar Composition |
1.pnt1 embryos had a 40% reduction in crystalline cellulose (117 nmol glucose/mg dry weight) compared with 196 nmol/mg in wild-type embryos. By contrast, pnt1 embryos contained 93 nmol/mg dry weight of uronic acid (the principal component of pectin), more than twice as much as wild-type embryos (41 nmol/mg). 2.Mutants empryo showed a 60% increase in total neutral sugars/mg dry weight. |
| Reference | Gillmor CS, Lukowitz W, Brininstool G, Sedbrook JC, Hamann T, Poindexter P, Somerville C. Glycosylphosphatidylinositol-anchored proteins are required for cell wall synthesis and morphogenesis in Arabidopsis. Plant Cell. 2005 Apr;17(4):1128-40. |