Specific HR‐associated recognition of secreted proteins from Cladosporium fulvum occurs in both host and non‐host plants

Abstract

SummaryThe resistance of tomato (Lycopersicon esculentum) to the pathogenic fungus Cladosporium fulvum complies with the gene-for-gene concept. Host resistance is based on speci®c recognition of extracellular fungal proteins, resulting in a hypersensitive response (HR). Five proteins secreted by C. fulvum were puri®ed and the encoding cDNA clone was obtained from two novel ones among them. Various tomato breeding lines and accessions of Lycopersicon pimpinellifolium were tested for their recognitional speci®city by injection of the puri®ed proteins or potato virus X-based expression of the cDNA. We found that HR-associated recognition of one or more of these proteins, in addition to recognition of the racespeci®c elicitors AVR4 and AVR9 of C. fulvum, occurs among Lycopersicon species. Studies on the inheritance of this recognition con®rmed that single dominant genes are involved. Furthermore, one of the extracellular proteins of C. fulvum is speci®cally recognized by Nicotiana paniculata, which is not a host for C. fulvum. These results indicate that plants have a highly effective surveillance system for the presence of`foreign' proteins, which, together with the high mutation rate of pathogens, can explain the complex gene-for-gene relationships frequently observed in pathosystems.

Intragenic recombination generated two distinct Cf genes that mediate AVR9 recognition in the natural population of Lycopersicon pimpinellifolium

“…In a previous study, six accessions of Lp were identified as AVR9-responsive (15). We chose one AVR9-responsive plant of accession LA1301 to characterize the Hcr9 mediating AVR9 recognition.…”

“…The Cf-9 locus has been introgressed into cultivated tomato (Lycopersicon esculentum) from its wild relative Lycopersicon pimpinellifolium (Lp) (14). Lp contains many different recognitional specificities for proteins of C. fulvum and was used as a rich germplasm for Cf R genes (15). The natural habitat of Lp is a narrow, 2,500-km-long coastal area of Ecuador and Peru, bordered by the Pacific Ocean and the Andes Mountains (16).…”

High affinity recognition of a Phytophthora protein by Arabidopsis via an RGD motif

“…So far, very few RGD-containing proteins from plant pathogens have been described. We know of one virus protein, the precursor of G1 and G2 glycoproteins of the tomato spotted wilt virus [30]; two fungal proteins, ECP5 from Cladosporium fulvum [31] and Ptr ToxA from Pyrenophora tritici-repentis [14]; and one oomycete protein, IPI-O from Phytophthora infestans [19]. ECP5, Ptr ToxA and IPI-O are secreted proteins and also G1 and G2 are located outside the virus namely in the virus envelope membrane.…”

Cladosporium fulvum CfHNNI1 induces hypersensitive necrosis, defence gene expression and disease resistance in both host and nonhost plants

“…Preformed defence mechanisms include formation of plant cytoskeleton and barriers against pathogenic invasion (Kobayashi et al 1997;Yun et al 2003), and constitutive accumulation of a variety of secondary metabolites, especially those with antimicrobial activity (Osbourn 1996). Induced defence mechanisms comprise of accumulation of components involved in preformed defence mechanisms, activation of plant defence signalling, accumulation of reactive oxygen species and initiation of hypersensitive response (HR) in some cases (Kamoun et al 1999;Heath 2000;Lauge et al 2000;Mellersh et al 2002;Mellersh and Heath 2003;Christopher-Kozjan and Heath 2003;Shimizu et al 2003;Mysore and Ryu 2004). Some essential nonhost resistance genes have recently been cloned from Arabidopsis.…”

“…During infection the pathogen secrets proteins into plant extracellular space. Upon expression, the gene encoding one of the secreted proteins, ECP2, induces HR and resistance to recombinant Potato virus X in nonhost plant Nicotiana paniculata (Lauge et al 2000), probably through recognition by Cf-ECP2 (Lauge et al 1998). Therefore ECP2 might be a specific Avr elicitor of C. fulvum nonhost resistance.…”