The multivesicular body-localized GTPase ARFA1b/1c is important for callose deposition and ROR2 syntaxin-dependent preinvasive basal defense in barley.
Host cell vesicle traffic is essential for the interplay between plants and microbes. ADP-ribosylation factor (ARF) GTPases are required for vesicle budding, and we studied the role of these enzymes to identify important vesicle transport pathways in the plant-powdery mildew interaction. A combination of transient-induced gene silencing and transient expression of inactive forms of ARF GTPases provided evidence that barley (Hordeum vulgare) ARFA1b/1c function is important for preinvasive penetration resistance against powdery mildew, manifested by formation of a cell wall apposition, named a papilla. Mutant studies indicated that the plasma membrane-localized REQUIRED FOR MLO-SPECIFIED RESISTANCE2 (ROR2) syntaxin, also important for penetration resistance, and ARFA1b/1c function in the same vesicle transport pathway. This was substantiated by a requirement of ARFA1b/1c for ROR2 accumulation in the papilla. ARFA1b/1c is localized to multivesicular bodies, providing a functional link between ROR2 and these organelles in penetration resistance. During Blumeria graminis f sp hordei penetration attempts, ARFA1b/1c-positive multivesicular bodies assemble near the penetration site hours prior to the earliest detection of callose in papillae. Moreover, we showed that ARFA1b/1c is required for callose deposition in papillae and that the papilla structure is established independently of ARFA1b/1c. This raises the possibility that callose is loaded into papillae via multivesicular bodies, rather than being synthesized directly into this cell wall apposition.
Department of Agriculture and Ecology, Faculty of Life Sciences, University of Copenhagen, 1871 Frederiksberg C, Copenhagen, Denmark.
Henrik
H
Böhlenius
Sara M
SM
Mørch
Dale
D
Godfrey
Mads E
ME
Nielsen
Hans
H
Thordal-Christensen
D020727:ADP-Ribosylation Factors / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport; D011992:Endosomes / Q000378:metabolism; D020868:Gene Silencing; D005936:Glucans / Q000378:metabolism*; D001467:Hordeum / Q000033:anatomy & histology / Q000276:immunology* / Q000382:microbiology; D057146:Multivesicular Bodies / Q000201:enzymology*; D010802:Phylogeny; D010935:Plant Diseases / Q000276:immunology; D018515:Plant Leaves / Q000033:anatomy & histology / Q000201:enzymology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D050765:Qa-SNARE Proteins / Q000378:metabolism*; D057050:Receptor Tyrosine Kinase-like Orphan Receptors / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism
D029681:Arabidopsis Proteins; D005936:Glucans; D010940:Plant Proteins; D050765:Qa-SNARE Proteins; D011993:Recombinant Fusion Proteins; C048306:callose; D057050:Receptor Tyrosine Kinase-like Orphan Receptors; C495672:Ara7 protein, Arabidopsis; D020727:ADP-Ribosylation Factors; D020691:rab GTP-Binding Proteins