Arabidopsis thaliana FLA4 functions as a glycan-stabilized soluble factor via its carboxy-proximal Fasciclin 1 domain

. XUE, VEITH, ABAS, TRYFONA, MARESCH, ESTEVEZ J.M., DUPREE, ALTMANN, STRASSER R & SEIFERT G

PLANT JOURNAL

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2017

0960-7412

Fasciclin like arabinogalactan proteins (FLAs) are involved in numerous important functionsin plants but the relevance of their complex structure to physiological function and cellularfate is unresolved. Using a fully functional fluorescent version of Arabidopsis thaliana FLA4we show that this protein is localized at the plasma membrane as well as in endosomes andsoluble in the apoplast. FLA4 is likely to be GPI-anchored, is highly N-glycosylated andcarries two O-glycan epitopes previously associated with AGPs. The activity of FLA4 wasresistant against deletion of the amino-proximal fasciclin 1 domain and was unaffected byremoval of the GPI-modification signal, a highly conserved N-glycan or the deletion ofpredicted O-glycosylation sites. Nonetheless these structural changes dramatically decreasedER-exit and plasma membrane localization of FLA4, with N-glycosylation acting at the levelof ER-exit and O-glycosylation controlling post secretory fate. We show that FLA4 actspredominantly by molecular interactions involving its carboxy-proximal fasciclin 1 domainand that its amino-proximal fasciclin 1 domain is required for stabilization of plasmamembrane localization. FLA4 functions as a soluble glycoprotein via its carboxy-proximalFas1 domain and its normal cellular trafficking depends on N- and O-glycosylation.