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Fungal pathogens secrete an inhibitor protein that distinguishes isoforms of plant pathogenesis‐related endo‐β‐1,3‐glucanases
Author(s) -
Ham KyungSik,
Wu ShengCheng,
Darvill Alan G.,
Albersheim Peter
Publication year - 1997
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 - 10.1046/j.1365-313x.1997.11020169.x
Subject(s) - glucanase , pathogenesis related protein , chitinase , microbiology and biotechnology , mycelium , secretion , biology , phytophthora sojae , glucosyltransferase , enzyme , elicitor , biochemistry , secretory protein , pathogen , pathogenesis , gene , gene expression , botany , immunology
Plant endo‐β‐1,3‐glucanases and chitinases inhibit the growth of some fungi and generate elicitor‐active oligosaccharides while depolymerizing polysaccharides of mycelial walls. Overexpression of the endo‐β‐1,3‐glucanases and/ or chitinases in transgenic plants provides, in some cases, increased protection against fungal pathogens. However, most of the phytopathogenic fungi that have been tested in vitro are resistant to endo‐β‐1,3‐glucanases and chitinases. Furthermore, some phytopathogenic fungi whose growth is inhibited by these enzymes are able to overcome the effect of these enzymes over a period of hours, indicating an ability of those fungi to adapt to the enzymes. Evidence is presented indicating that fungal pathogens secrete proteins that inhibit selective plant endo‐β‐1,3‐glucanases.A glucanase inhibitor protein (GIP‐1) has been purified to homogeneity from the culture fluid of the fungal pathogen of soybeans, Phytophthora sojae f. sp. glycines (Psg), and two basic pathogenesis‐related endo‐β‐1,3‐glucanases (EnGL soy ‐A and EnGL soy ‐B) have been purified from soybean seedlings. GIP‐1 inhibits EnGL soy ‐A but not EnGL soy ‐B. Moreover, GIP‐1 does not inhibit endo‐β‐1,3‐glucanases secreted by Psg itself nor does GIP‐1 inhibit PR‐2c, a pathogenesis‐related endo‐β‐1,3‐glucanase of tobacco. Evidence is presented that Psg secretes other GIPs that inhibit other endo‐β‐1,3‐glucanase(s) of soybean. Furthermore, GIP‐1 does not exhibit proteolytic activity but does appear to physically bind to EnGL soy ‐A. The results reported herein demonstrate specific interactions between gene products of the host and pathogen and establish the need to consider fungal proteins that inhibit plant endo‐β‐1,3‐glucanases when attempting to use the genes encoding endo‐β‐1,3‐glucanases to engineer resistance to fungi in transgenic plants.