Class I alpha-mannosidases are required for N-glycan processing and root development in Arabidopsis thaliana.
In eukaryotes, class I alpha-mannosidases are involved in early N-glycan processing reactions and in N-glycan-dependent quality control in the endoplasmic reticulum (ER). To investigate the role of these enzymes in plants, we identified the ER-type alpha-mannosidase I (MNS3) and the two Golgi-alpha-mannosidase I proteins (MNS1 and MNS2) from Arabidopsis thaliana. All three MNS proteins were found to localize in punctate mobile structures reminiscent of Golgi bodies. Recombinant forms of the MNS proteins were able to process oligomannosidic N-glycans. While MNS3 efficiently cleaved off one selected alpha1,2-mannose residue from Man(9)GlcNAc(2), MNS1/2 readily removed three alpha1,2-mannose residues from Man(8)GlcNAc(2). Mutation in the MNS genes resulted in the formation of aberrant N-glycans in the mns3 single mutant and Man(8)GlcNAc(2) accumulation in the mns1 mns2 double mutant. N-glycan analysis in the mns triple mutant revealed the almost exclusive presence of Man(9)GlcNAc(2), demonstrating that these three MNS proteins play a key role in N-glycan processing. The mns triple mutants displayed short, radially swollen roots and altered cell walls. Pharmacological inhibition of class I alpha-mannosidases in wild-type seedlings resulted in a similar root phenotype. These findings show that class I alpha-mannosidases are essential for early N-glycan processing and play a role in root development and cell wall biosynthesis in Arabidopsis.
Liebminger
Eva
E
Department of Applied Genetics and Cell Biology, University of Natural Resources and Applied Life Sciences, A-1190 Viena, Austria.
Hüttner
Silvia
S
Vavra
Ulrike
U
Fischl
Richard
R
Schoberer
Jennifer
J
Grass
Josephine
J
Blaukopf
Claudia
C
Seifert
Georg J
GJ
Altmann
Friedrich
F
Mach
Lukas
L
Strasser
Richard
R
D000818:Animals; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002473:Cell Wall / Q000378:metabolism; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000235:genetics; D004721:Endoplasmic Reticulum / Q000201:enzymology; D005816:Genetic Complementation Test; D006031:Glycosylation; D006056:Golgi Apparatus / Q000201:enzymology; D016254:Mutagenesis, Insertional; D009154:Mutation; D010802:Phylogeny; D018517:Plant Roots / Q000201:enzymology / Q000254:growth & development*; D011134:Polysaccharides / Q000378:metabolism*; D018749:RNA, Plant / Q000235:genetics; D018411:Spodoptera / Q000166:cytology; D013379:Substrate Specificity; D043323:alpha-Mannosidase / Q000235:genetics / Q000378:metabolism*
D029681:Arabidopsis Proteins; D004269:DNA, Bacterial; D011134:Polysaccharides; D018749:RNA, Plant; C036483:T-DNA; D043323:alpha-Mannosidase