title: The intercellular biotrophic leaf pathogen Cymadothea trifolii locally degrades pectins, but not cellulose or xyloglucan in cell walls of Trifolium repens.
abstract: The intercellular ascomycetous pathogen Cymadothea trifolii, causing sooty blotch of clover, proliferates within leaves of Trifolium spp. and produces a complex structure called interaction apparatus (IA) in its own hyphae. Opposite the IA the plant plasmalemma invaginates to form a bubble. Both structures are connected by a tube with an electron-dense sheath. Using immunocytochemistry on high-pressure frozen and freeze-substituted samples, we examined several plant and fungal cell wall components, including those in new host wall appositions at the interaction site, as well as a fungal polygalacturonase. Within the tube linking IA and host bubble, labelling was obtained for cellulose and xyloglucan but not for rhamnogalacturonan-I and homogalacturonans. The IA labelled for chitin and beta-1,3-glucans, and for a fungal polygalacturonase. Plant wall appositions reacted with antibodies against callose, xyloglucans and rhamnogalacturonan-I. Cymadothea trifolii partly degrades the host cell wall. Structural elements remain intact, but the pectin matrix is dissolved. A fungal polygalacturonase detected in the IA is probably a key factor in this process. Owing to the presence of chitin and beta-1,3-glucans, the IA itself is considered an apoplastic compartment.
authors.affiliation: Universität Tübingen, Lehrstuhl Spezielle Botanik und Mykologie, Auf der Morgenstelle 1, D-72076 Tübingen, Germany. uwe.simon@uni-tuebingen.de
authors.forename: Uwe K
authors.initials: UK
authors.lastname: Simon
authors.forename: Robert
authors.initials: R
authors.lastname: Bauer
authors.forename: Danny
authors.initials: D
authors.lastname: Rioux
authors.forename: Marie
authors.initials: M
authors.lastname: Simard
authors.forename: Franz
authors.initials: F
authors.lastname: Oberwinkler
mesh_terms: D001203:Ascomycota / Q000378:metabolism* / Q000648:ultrastructure; D002473:Cell Wall / Q000378:metabolism; D002482:Cellulose / Q000378:metabolism; D005936:Glucans / Q000378:metabolism; D025301:Hyphae / Q000378:metabolism; D007150:Immunohistochemistry; D010368:Pectins / Q000378:metabolism; D010935:Plant Diseases / Q000382:microbiology; D029921:Trifolium / Q000382:microbiology* / Q000648:ultrastructure; D014990:Xylans / Q000378:metabolism
chemical_list: D005936:Glucans; D014990:Xylans; C029353:xyloglucan; D010368:Pectins; D002482:Cellulose