Abstract
In plant cells, glycans attached to asparagine (N) residues of proteins undergo various modifications in the endoplasmic reticulum and the Golgi apparatus. The N-glycan modifications in the Golgi apparatus result in complex N-glycans attached to membrane proteins, secreted proteins, and vacuolar proteins. Recently, we have investigated the role of complex N-glycans in plants using a series of Arabidopsis thaliana mutants affected in complex N-glycan biosynthesis.1 Several mutant plants including complex glycan 1 (cgl1) displayed a salt-sensitive phenotype during their root growth, which was associated with radial swelling and loss of apical dominance. Among the proteins whose N-glycans are affected by the cgl1 mutation is a membrane anchored β1,4-endoglucanse, KORRIGAN1/RADIAL SWELLING2 (KOR1/RSW2) involved in cellulose biosynthesis. The cgl1 mutation strongly enhanced the phenotype of a temperature sensitive allele of KOR1/RSW2 (rsw2-1) even at the permissive temperature. This establishes that plant complex N-glycan modification is important for the in vivo function of KOR1/RSW2. Furthermore, rsw2-1 as well as another cellulose biosynthesis mutant rsw1-1 exhibited also a salt-sensitive phenotype at the permissive temperature. Based on these findings, we propose that one of the mechanisms that cause salt-induced root growth arrest is dysfunction of cell wall biosynthesis that induces mitotic arrest in the root apical meristem.Addendum to: Kang JS, Frank J, Kang CH, Kajiura H, Vikram M, Ueda A, Kim S, Bahk JD, Triplett B, Fujiyama K, Lee SY, von Schaewen A, Koiwa H. Salt tolerance of Arabidopsis thaliana requires maturation of N-glycosylated proteins in the Golgi apparatus. Proc Natl Acad Sci USA 2008; 105:5933-8.
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