IFIBYNE   05513
INSTITUTO DE FISIOLOGIA, BIOLOGIA MOLECULAR Y NEUROCIENCIAS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Proline hydroxylation on Hydroxyproline Rich-Glycoproteins (HRGPs) mediated by P4Hs is crucial for polarized growth in Arabidopsis root hairs.
Autor/es:
SILVIA MELINA VELÁSQUEZ1, MARTINIANO M. RICARDI1, JAVIER GLOAZZO DOROSZ1, NORBERTO D. IUSEM1, JOSE M. ESTEVEZ1
Lugar:
La Plata Argentina
Reunión:
Congreso; XXVIII Reunion Argentina de Fisiologia Vegetal; 2010
Institución organizadora:
Asociacion Argentina de Fisiologia Vegetal
Resumen:
Prolyl 4-hydroxylases (P4Hs) catalyze proline hydroxylation, a major post-translational modification, of hydroxyproline-rich glycoproteins (HRGPs) like extensins (EXTs), cell wall basic glycoproteins. P4Hs are important because they define O-glycosylation sites on HRGPs. However, precise biological roles of post-translational modifications on plant specific HRGPs have remained elusive. We show that pharmacological inhibition of AtP4Hs activity as well as genetic disruption of different root hair (rh) P4Hs (generating rhp4h2, rhp4h5 and rhp4h13 mutants) were able to partially block polarized expansion in root hairs in Arabidopsis. Genetic complementation of each of these mutants restored root hair growth to wild type levels. By yeast two-hybrid assays, rhP4H5 was identified to physically interact with a leucine-rich protein containing several extensin motifs and with other poly-proline II-rich proteins, suggesting that rhEXTs are the direct targets of rhP4H5. Mutant analysis of four recently discovered glycosyltransferases that can arabinosylate EXTs (rra1-3 and xeg113-2) phenocopy rhp4hs, thus supporting the hypothesis of a crucial role of O-glycans on rhEXTs as key regulators of cell elongation in root hairs. Moreover, by means of differential microarray analysis of several root hair mutants and also by co-expression network analysis, several type-II rhEXTs with obvious root hair phenotypes were identified, which is indicative of a complex genetic network modulating root hair elongation at the cell wall level. Therefore, AtP4Hs, which modulate proline hydroxylation on root hair extensins (rhEXTs), are critical for root hair elongation growth. The control of growth by O-glycosylated EXTs may represent a more general mechanism for regulating cell expansion in different plant cell types.