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The Receptor for the Fungal Elicitor Ethylene-Inducing Xylanase Is a Member of a Resistance-Like Gene Family

Summary: The Receptor for the Fungal Elicitor Ethylene-Inducing
Xylanase Is a Member of a Resistance-Like Gene Family
in Tomato
Mily Ron and Adi Avni1
Department of Plant Sciences, Tel Aviv University, Tel Aviv 69978, Israel
An ethylene-inducing xylanase (EIX) is a potent elicitor of plant defense responses in specific cultivars of tobacco (Nicotiana
tabacum) and tomato (Lycopersicon esculentum). The LeEix locus in tomatoes was characterized by map-based cloning,
which led to the identification of a novel gene cluster from which two members (LeEix1 and LeEix2) were isolated. Similar to
the tomato Ve resistance genes in tomato plants, the deduced amino acid sequences encoded by LeEix1 and LeEix2 contain
a Leu zipper, an extracellular Leu-rich repeat domain with glycosylation signals, a transmembrane domain, and a C-terminal
domain with a mammalian endocytosis signal. Silencing expression of the LeEix genes prevented the binding of EIX to cells
of an EIX-responsive plant and thus inhibited the hypersensitive response. Overexpression of either LeEix1 or LeEix2 genes
in EIX-nonresponsive tobacco plants enabled the binding of EIX, although only LeEix2 could transmit the signal that induced
the hypersensitive response. Overexpressing LeEix2 in mammalian COS-7 cells enables binding of EIX, indicating physical
interaction between the EIX elicitor and LeEix2 gene product. Structural analysis of the LeEix proteins suggests that they
belong to a class of cell-surface glycoproteins with a signal for receptor-mediated endocytosis. Mutating the endocytosis
signal in LeEix2 (Tyr 993 to Ala) abolished its ability to induce the hypersensitive response, suggesting that endocytosis
plays a key role in the signal transduction pathway.
Plants are constantly under attack by such pathogens as


Source: Avni, Adi - Department of Plant Sciences, Tel Aviv University


Collections: Biology and Medicine