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A Point Mutation in the Ethylene-Inducing Xylanase Elicitor Inhibits the -1-4-Endoxylanase Activity But Not the
 

Summary: A Point Mutation in the Ethylene-Inducing Xylanase Elicitor
Inhibits the -1-4-Endoxylanase Activity But Not the
Elicitation Activity1
Noa Furman-Matarasso, Eitan Cohen, Quansheng Du, Nor Chejanovsky, Uri Hanania, and Adi Avni*
Department of Plant Sciences, Tel-Aviv University, Tel-Aviv 69978, Israel (N.F.-M., E.C., U.H., A.A.); and
Department of Entomology, Institute of Plant Protection, The Volcani Center,
Bet-Dagan 50250, Israel (Q.D., N.C.)
Ethylene-inducing xylanase (EIX) elicits plant defense responses
in certain tobacco (Nicotiana tabacum) and tomato cultivars in
addition to its xylan degradation activity. It is not clear, however,
whether elicitation occurs by cell wall fragments released by the
enzymatic activity or by the xylanase protein interacting directly
with the plant cells. We cloned the gene encoding EIX protein and
overexpressed it in insect cells. To determine the relationship be-
tween the two activities, substitution of amino acids in the xylanase
active site was performed. Substitution at glutamic acid-86 or -177
with glutamine (Gln), aspartic acid (Asp), or glycine (Gly) inhibited
the -1-4-endoxylanase activity. Mutants having Asp-86 or Gln-177
also lost the ability to induce the hypersensitive response and
ethylene biosynthesis. However, mutants having Gln-86, Gly-86,

  

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

 

Collections: Biology and Medicine