title: Entry mode-dependent function of an indole glucosinolate pathway in Arabidopsis for nonhost resistance against anthracnose pathogens.
abstract: When faced with nonadapted fungal pathogens, Arabidopsis thaliana mounts nonhost resistance responses, which typically result in the termination of early pathogenesis steps. We report that nonadapted anthracnose fungi engage two alternative entry modes during pathogenesis on leaves: turgor-mediated invasion beneath melanized appressoria, and a previously undiscovered hyphal tip-based entry (HTE) that is independent of appressorium formation. The frequency of HTE is positively regulated by carbohydrate nutrients and appears to be subject to constitutive inhibition by the fungal mitogen-activated protein kinase (MAPK) cascade of MAPK ESSENTIAL FOR APPRESSORIUM FORMATION1. The same MAPK cascade is essential for appressorium formation. Unexpectedly, the Arabidopsis indole glucosinolate pathway restricts entry of the nonadapted anthracnose fungi only when these pathogens employ HTE. Arabidopsis mutants defective in indole glucosinolate biosynthesis or metabolism support the initiation of postinvasion growth of nonadapted Colletotrichum gloeosporioides and Colletotrichum orbiculare. However, genetic disruption of Colletotrichum appressorium formation does not permit HTE on host plants. Thus, Colletotrichum appressoria play a critical role in the suppression of preinvasion plant defenses, in addition to their previously described role in turgor-mediated plant cell invasion. We also show that HTE is the predominant morphogenetic response of Colletotrichum at wound sites. This implies the existence of a fungal sensing system to trigger appropriate morphogenetic responses during pathogenesis at wound sites and on intact leaf tissue.
authors.affiliation: Department of Plant-Microbe Interactions, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Kei
authors.initials: K
authors.lastname: Hiruma
authors.forename: Mariko
authors.initials: M
authors.lastname: Onozawa-Komori
authors.forename: Fumika
authors.initials: F
authors.lastname: Takahashi
authors.forename: Makoto
authors.initials: M
authors.lastname: Asakura
authors.forename: Pawel
authors.initials: P
authors.lastname: Bednarek
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Okuno
authors.forename: Paul
authors.initials: P
authors.lastname: Schulze-Lefert
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Takano
mesh_terms: D017360:Arabidopsis / Q000378:metabolism* / Q000382:microbiology; D004705:Endocytosis; D005961:Glucosinolates / Q000378:metabolism*; D007211:Indoles / Q000378:metabolism*
chemical_list: D005961:Glucosinolates; D007211:Indoles