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The genetic and biochemical basis of...

Griffitts, Joel Shelby.

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The genetic and biochemical basis of resistance to Bacillus thuringiensis crystal toxins.

Record Type:	Electronic resources : Monograph/item
Title/Author:	The genetic and biochemical basis of resistance to Bacillus thuringiensis crystal toxins./
Author:	Griffitts, Joel Shelby.
Description:	132 p.
Notes:	Source: Dissertation Abstracts International, Volume: 65-01, Section: B, page: 0055.
Contained By:	Dissertation Abstracts International65-01B.
Subject:	Biology, Genetics. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3120445

The genetic and biochemical basis of resistance to Bacillus thuringiensis crystal toxins.
Griffitts, Joel Shelby.

The genetic and biochemical basis of resistance to Bacillus thuringiensis crystal toxins. - 132 p.

Source: Dissertation Abstracts International, Volume: 65-01, Section: B, page: 0055.

Thesis (Ph.D.)--University of California, San Diego, 2004.

Cytolytic pore-forming toxins are utilized by a number of pathogenic bacteria, and are defined by their ability to disrupt the membranes of target host cells. Bacillus thuringiensis is an insect and nematode pathogen that employs a type of pore-forming toxin known as Crystal (Cry) toxin (also known as Bt toxin). Cry toxins have potent and destructive effects on invertebrate gut cells but are harmless to humans. Using the model invertebrate Caenorhabditis elegans, I have investigated how resistance to Cry toxins develops. C. elegans is susceptible to several Cry toxins, including Cry5B. We screened for C. elegans mutants that are resistant to Cry5B. To date these mutants have defined five genes (bre-1 through bre-5, for B&barbelow;t toxin resistant), each of which is required for Cry5B susceptibility. I identified bre-5 as a glycosyltransferase gene, and found that it acts in the animal's intestinal cells. It appears to enable appropriate association of Cry5B with intestinal cell membranes. This finding suggested that carbohydrate modifications on the target cell potentiate Cry toxin action, perhaps by direct interaction of the toxin with some carbohydrate receptor. This idea facilitated the discovery that bre-2, bre-3, and bre-4 also encode glycosyltransferases, that they also function in the intestine to facilitate Cry5B intoxication, and that, with bre-5 , these genes constitute a single genetic pathway. Since genes similar to bre-3 and bre-5 had been proposed to be involved in glycolipid synthesis, I analyzed the lipids of bre mutants and found that the bre genes are indeed required for the synthesis of glycolipids. With the development of Cry5B binding assays, I discovered that Cry5B interacts directly with the same glycolipids that are absent in bre mutants. This interaction is important for Cry toxin function, and is specifically interrupted in vitro and in vivo by galactose and related compounds. That bre mutants are also resistant to the distantly related toxin Cry14A suggests that glycolipid receptors are generally important for the mode of action of this important class of bacterial toxins. Finally, I show that a hookworm parasite possesses Cry5B glycolipid receptors, explaining previous data from our lab that Cry5B can affect animal parasitic nematodes.Subjects--Topical Terms:

1017730
Biology, Genetics.

The genetic and biochemical basis of resistance to Bacillus thuringiensis crystal toxins.
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100 1 $a Griffitts, Joel Shelby. $3 1948705
245 1 4 $a The genetic and biochemical basis of resistance to Bacillus thuringiensis crystal toxins.
300 $a 132 p.
500 $a Source: Dissertation Abstracts International, Volume: 65-01, Section: B, page: 0055.
500 $a Chair: Raffi V. Aroian.
502 $a Thesis (Ph.D.)--University of California, San Diego, 2004.
520 $a Cytolytic pore-forming toxins are utilized by a number of pathogenic bacteria, and are defined by their ability to disrupt the membranes of target host cells. Bacillus thuringiensis is an insect and nematode pathogen that employs a type of pore-forming toxin known as Crystal (Cry) toxin (also known as Bt toxin). Cry toxins have potent and destructive effects on invertebrate gut cells but are harmless to humans. Using the model invertebrate Caenorhabditis elegans, I have investigated how resistance to Cry toxins develops. C. elegans is susceptible to several Cry toxins, including Cry5B. We screened for C. elegans mutants that are resistant to Cry5B. To date these mutants have defined five genes (bre-1 through bre-5, for B&barbelow;t toxin resistant), each of which is required for Cry5B susceptibility. I identified bre-5 as a glycosyltransferase gene, and found that it acts in the animal's intestinal cells. It appears to enable appropriate association of Cry5B with intestinal cell membranes. This finding suggested that carbohydrate modifications on the target cell potentiate Cry toxin action, perhaps by direct interaction of the toxin with some carbohydrate receptor. This idea facilitated the discovery that bre-2, bre-3, and bre-4 also encode glycosyltransferases, that they also function in the intestine to facilitate Cry5B intoxication, and that, with bre-5 , these genes constitute a single genetic pathway. Since genes similar to bre-3 and bre-5 had been proposed to be involved in glycolipid synthesis, I analyzed the lipids of bre mutants and found that the bre genes are indeed required for the synthesis of glycolipids. With the development of Cry5B binding assays, I discovered that Cry5B interacts directly with the same glycolipids that are absent in bre mutants. This interaction is important for Cry toxin function, and is specifically interrupted in vitro and in vivo by galactose and related compounds. That bre mutants are also resistant to the distantly related toxin Cry14A suggests that glycolipid receptors are generally important for the mode of action of this important class of bacterial toxins. Finally, I show that a hookworm parasite possesses Cry5B glycolipid receptors, explaining previous data from our lab that Cry5B can affect animal parasitic nematodes.
590 $a School code: 0033.
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773 0 $t Dissertation Abstracts International $g 65-01B.
790 1 0 $a Aroian, Raffi V., $e advisor
790 $a 0033
791 $a Ph.D.
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856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3120445