Proline hydroxilation & O-arabinosylation on extensins: key post-translational modifications in root hair growth

VELASQUEZ SILVIA MELINA; ELIANA MARZOL; RICARDI MM; MANGANO S; DENITA JUAREZ SP; GLOAZZO DOROZ JA; SALGADO SALTER JD; BORASSI C; ESTÉVEZ JM

Ciudad Autonoma de Buenos Aires

Congreso; First Argentinean Symposium of Glycobiology "GlycoAR 2014"; 2014

Plant cell walls are composed of polysaccharides and hydroxyproline-rich glycoproteins including highly O-glycosylated extensins (EXTs) proteins. Our group has characterized several post-translational modifications (PMTs) of EXTs in the root hair cell in Arabidopsis thaliana The root hair is a single cell with polarized growth and it is responsible for the root's water and nutrient uptake. Previously, we had demonstrated that O-glycosylation on EXTs is essential for cell-wall self-assembly and, hence, root hair elongation. We have determined several molecular players involved in proline hydroxylation and subsequent 0- arabinosylation in EXTs. Currently, we showed further characterization of these PMTs. We found that in proline hydroxylation, only one prolyl-4-hydroxylase (P4H5) has a central role being able to compensate for the other missing P4Hs. Arabinosylation is also required for proper EXT function since our mutant lines presented lower levels of arabinose residues as well as shorter root hairs. In addition, we identified 2 apoplastic type-III peroxidases related to EXTs that could involved in the assembly of the EXT-extracellular network through the crosslinking of Tyr residues present in EXTs. We also observed reduced levels of Tyr-crosslinking in several mutant lines. Together these data represent a more profound understanding of how PMTs affects EXTs function in tip-growing cells.