AUTHOR=Veit Christiane , König Julia , Altmann Friedrich , Strasser Richard 

TITLE=Processing of the Terminal Alpha-1,2-Linked Mannose Residues From Oligomannosidic N-Glycans Is Critical for Proper Root Growth

JOURNAL=Frontiers in Plant Science

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2018.01807

DOI=10.3389/fpls.2018.01807

ISSN=1664-462X

ABSTRACT=<p><italic>N</italic>-glycosylation is an essential protein modification that plays roles in many diverse biological processes including protein folding, quality control and protein interactions. Despite recent advances in characterization of the <italic>N</italic>-glycosylation and <italic>N</italic>-glycan processing machinery our understanding of <italic>N</italic>-glycosylation related processes in plant development is limited. In <italic>Arabidopsis thaliana</italic>, failure of mannose trimming from oligomannosidic <italic>N</italic>-glycans in the endoplasmic reticulum (ER) and <italic>cis</italic>/medial-Golgi leads to a defect in root development in the <italic>mns123</italic> triple mutant. Here, we show that the severe root phenotype of <italic>mns123</italic> is restored in asparagine-linked glycosylation (ALG)-deficient plants with distinct defects in the biosynthesis of the lipid-linked oligosaccharide precursor. The root growth of these ALG-deficient plants is not affected by the α-mannosidase inhibitor kifunensine. Genetic evidence shows that the defect is uncoupled from the glycan-dependent ER-associated degradation (ERAD) pathway that removes misfolded glycoproteins with oligomannosidic <italic>N</italic>-glycans from the ER. Restoration of mannose trimming using a <italic>trans</italic>-Golgi targeted α-mannosidase suppresses the defect of <italic>mns123</italic> roots. These data suggest that processing of terminal mannose residues from oligomannosidic <italic>N</italic>-glycans is important for an unknown late-Golgi or post-Golgi process that is implicated in proper root formation.</p>