Effect of arabinogalactan proteins from the root caps of pea and Brassica napus on Aphanomyces euteiches zoospore chemotaxis and germination.
Root tips of many plant species release a number of border, or border-like, cells that are thought to play a major role in the protection of root meristem. However, little is currently known on the structure and function of the cell wall components of such root cells. Here, we investigate the sugar composition of the cell wall of the root cap in two species: pea (Pisum sativum), which makes border cells, and Brassica napus, which makes border-like cells. We find that the cell walls are highly enriched in arabinose and galactose, two major residues of arabinogalactan proteins. We confirm the presence of arabinogalactan protein epitopes on root cap cell walls using immunofluorescence microscopy. We then focused on these proteoglycans by analyzing their carbohydrate moieties, linkages, and electrophoretic characteristics. The data reveal (1) significant structural differences between B. napus and pea root cap arabinogalactan proteins and (2) a cross-link between these proteoglycans and pectic polysaccharides. Finally, we assessed the impact of root cap arabinogalactan proteins on the behavior of zoospores of Aphanomyces euteiches, an oomycetous pathogen of pea roots. We find that although the arabinogalactan proteins of both species induce encystment and prevent germination, the effects of both species are similar. However, the arabinogalactan protein fraction from pea attracts zoospores far more effectively than that from B. napus. This suggests that root arabinogalactan proteins are involved in the control of early infection of roots and highlights a novel role for these proteoglycans in root-microbe interactions.
Laboratoire Glycobiologie et Matrice Extracellulaire Végétale, Équipe d'Accueil 4358, Université de Rouen, 76821 Mont Saint Aignan, France.
Marc Antoine
MA
Cannesan
Caroline
C
Durand
Carole
C
Burel
Christophe
C
Gangneux
Patrice
P
Lerouge
Tadashi
T
Ishii
Karine
K
Laval
Marie-Laure
ML
Follet-Gueye
Azeddine
A
Driouich
Maïté
M
Vicré-Gibouin
D044744:Aphanomyces / Q000166:cytology* / Q000187:drug effects / Q000254:growth & development*; D029688:Brassica napus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism* / Q000382:microbiology; D002473:Cell Wall / Q000187:drug effects / Q000378:metabolism; D011232:Chemical Precipitation; D002633:Chemotaxis / Q000187:drug effects*; D004591:Electrophoresis, Polyacrylamide Gel; D005960:Glucosides / Q000378:metabolism; D008856:Microscopy, Fluorescence; D009005:Monosaccharides / Q000737:chemistry / Q000378:metabolism; D009088:Mucoproteins / Q000737:chemistry / Q000494:pharmacology*; D018532:Pisum sativum / Q000166:cytology / Q000187:drug effects / Q000378:metabolism* / Q000382:microbiology; D010696:Phloroglucinol / Q000031:analogs & derivatives / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry / Q000494:pharmacology; D018518:Plant Root Cap / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*
D005960:Glucosides; D009005:Monosaccharides; D009088:Mucoproteins; D010940:Plant Proteins; C104977:Yariv reagent; C006619:arabinogalactan proteins; D010696:Phloroglucinol