Glycoproteins promoted by brassinosteroids are crucial for cell expansion

GLOAZZO DOROSZ J; VELASQUEZ SM; SALGADO SALTER J; ESTEVEZ JM

Mar del Plata

Congreso; XXIX Reunión Argentina de Fisiología Vegetal; 2012

Sociedad Argentina de Fisiología Vegetal

Several of plant cells functions are sustained by the integrity of cell walls. The plant primary cell wall consists on a network of cellulose microfibrils, xyloglucans, pectins, and hydroxyproline-rich glycoproteins (HRGPs). Many proline units are converted to 4-hydroxyproline in HRGPs by the action of prolyl 4-hydroxylase (P4Hs). There are specific O-glycosyl transferases associated to HRGP that attach sugars to the O-glycan chain. It has described that the O-glycosylation of the hydroxyproline residues is needful for the correct folding of HRGPs and for the best interaction on cell wall. The hypocotyl elongation exclusively depends of cell expansion, which is promoted by many factors that includes turgor pressure causing changes in the primary cell wall extensibility. In order to study in detail how plant cells expand, we choose to work with hypocotyls grown in dark which have 100-fold enhanced cell expansion when compared with other plant cell types. We have identified few T-DNA HRGPs mutant lines that have a deficient hypocotyl elongation when compared to Wt-Columbia 0 (Wt Col-0). Furthermore, when plants Wt-Col 0 were treated with chemical inhibitor of P4Hs, the length of hypocotyls resulted much shorter than normal phenotype. In addition, the putative deficiency of some sugars in the HRGP O-glycans produced a less of the hypocotyl elongation also. As a consequence, the proline conversion to 4-hydroxyproline as well as the O-glycosylation of hydoxyproline, are determinant for the hypocotyl complete elongation. Additionally, we are starting to look at the hormonal regulation of the HRGPs genes identified. Based on all these results, it is clear that proline hydroxylation and the correct O-glycosylation of HRGPs, are crucial for plant cell expansion.