The PEN1 syntaxin defines a novel cellular compartment upon fungal attack and is required for the timely assembly of papillae.
Attack by the host powdery mildew Erysiphe cichoracearum usually results in successful penetration and rapid proliferation of the fungus on Arabidopsis. By contrast, the nonhost barley powdery mildew Blumeria graminis f. sp. hordei (Bgh) typically fails to penetrate Arabidopsis epidermal cells. In both instances the plant secretes cell wall appositions or papillae beneath the penetration peg of the fungus. Genetic screens for mutations that result in increased penetration of Bgh on Arabidopsis have recently identified the PEN1 syntaxin. Here we examine the role of PEN1 and of its closest homologue, SYP122, identified as a syntaxin whose expression is responsive to infection. pen1 syp122 double mutants are both dwarfed and necrotic, suggesting that the two syntaxins have overlapping functions. Although syp122-1 and the cell wall mur mutants have considerably more pronounced primary cell wall defects than pen1 mutants, these have relatively subtle or no effects on penetration resistance. Upon fungal attack, PEN1 appears to be actively recruited to papillae, and there is a 2-h delay in papillae formation in the pen1-1 mutant. We conclude that SYP122 may have a general function in secretion, including a role in cell wall deposition. By contrast, PEN1 appears to have a basal function in secretion and a specialized defense-related function, being required for the polarized secretion events that give rise to papilla formation.
Assaad
Farhah F
FF
Department of Plant Biology, Carnegie Institution, Stanford, CA 94305, USA. Farhah@botanik.biologie
Qiu
Jin-Long
JL
Youngs
Heather
H
Ehrhardt
David
D
Zimmerli
Laurent
L
Kalde
Monika
M
Wanner
Gehard
G
Peck
Scott C
SC
Edwards
Herb
H
Ramonell
Katrina
K
Somerville
Chris R
CR
Thordal-Christensen
Hans
H
D017360:Arabidopsis / Q000378:metabolism / Q000382:microbiology*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002460:Cell Line; D002473:Cell Wall / Q000378:metabolism; D005658:Fungi / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006720:Homozygote; D007113:Immunity, Innate; D015151:Immunoblotting; D008565:Membrane Proteins / Q000378:metabolism / Q000502:physiology*; D018613:Microscopy, Confocal; D009154:Mutation; D009336:Necrosis; D010641:Phenotype; D010935:Plant Diseases; D019441:Plant Epidermis / Q000382:microbiology; D018515:Plant Leaves / Q000382:microbiology; D010940:Plant Proteins / Q000737:chemistry; D050765:Qa-SNARE Proteins; D050600:SNARE Proteins; D013997:Time Factors; D014158:Transcription, Genetic; D033921:Vesicular Transport Proteins / Q000378:metabolism
D029681:Arabidopsis Proteins; D008565:Membrane Proteins; C479425:PEN1 protein, Arabidopsis; D010940:Plant Proteins; D050765:Qa-SNARE Proteins; D050600:SNARE Proteins; D033921:Vesicular Transport Proteins; D049452:Green Fluorescent Proteins