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Gene shuffling‐generated and natural variants of the tomato resistance gene Cf ‐ 9 exhibit different auto‐necrosis‐inducing activities in Nicotiana species
Author(s) -
Wulff Brande B.H.,
Kruijt Marco,
Collins Peter L.,
Thomas Colwyn M.,
Ludwig Andrea A.,
De Wit Pierre J.G.M.,
Jones Jonathan D.G.
Publication year - 2004
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/j.1365-313x.2004.02268.x
Subject(s) - nicotiana benthamiana , biology , gene , nicotiana , hypersensitive response , genetics , gene family , r gene , lycopersicon , plant disease resistance , gene expression , botany , solanaceae
Summary Tomato Cf genes encode membrane‐bound proteins with extracellular leucine‐rich repeats, and confer resistance to the fungal tomato pathogen Cladosporium fulvum , and a hypersensitive response (HR) to C. fulvum ‐derived race‐specific elicitors. Several Cf genes, including Cf ‐ 4 and Cf ‐ 9 , are members of the highly homologous Hcr9 ( h omologues of C . fulvum r esistance gene Cf ‐ 9 ) gene family. Hcr9 s evolve mainly by sequence exchange between paralogues, by which novel Cf genes may be generated. To mimic this aspect of natural evolution, we generated chimeras between multiple Hcr9 s in vitro by gene shuffling. The shufflants were tested for novel specificities by transient expression in Nicotiana benthamiana . Many shufflants induced an HR in the absence of fungal elicitors and were designated auto‐activators. We also identified two natural Hcr9 auto‐activators in the wild tomato species Lycopersicon peruvianum , which induced an HR upon expression in N. benthamiana . The Hcr9 auto‐activators exhibit different auto‐necrosis‐inducing specificities in five selected species of the Nicotiana genus, and they were shown to function in the same signalling pathway as Cf ‐ 9 . Auto‐activating alleles of nucleotide binding site–leucine‐rich repeat genes and the protein kinase Pto were previously described. The auto‐activators described here, belonging to the Cf ‐like structural class of resistance genes, shed light on this important phenotype and may be used as tools to unravel the mechanisms by which this class of resistance proteins function.