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Applied and Environmental Microbiology, April 2000, p. 1559-1563, Vol. 66, No. 4
Plant Research International, 6700 AA
Wageningen, The Netherlands
Received 20 September 1999/Accepted 12 January 2000
In order to test our hypothesis that Bacillus
thuringiensis delta-endotoxin Cry1Ca domain III functions as a
determinant of specificity for Spodoptera exigua,
regardless of the origins of domains I and II, we have constructed by
cloning and in vivo recombination a collection of hybrid proteins
containing domains I and II of various Cry1 toxins combined with domain
III of Cry1Ca. Cry1Ab, Cry1Ac, Cry1Ba, Cry1Ea, and Cry1Fa all become
more active against S. exigua when their domain III is
replaced by (part of) that of Cry1Ca. This result shows that domain III
of Cry1Ca is an important and versatile determinant of S. exigua specificity. The toxicity of the hybrids varied by a
factor of 40, indicating that domain I and/or II modulate the activity
as well. Cry1Da-Cry1Ca hybrids were an exception in that they were not
significantly active against S. exigua or Manduca
sexta, whereas both parental proteins were highly toxic.
Incidentally, in a Cry1Ba-Cry1Ca hybrid, Cry1Ca domain III can also
strongly increase toxicity for M. sexta.
0099-2240/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Bacillus thuringiensis Delta-Endotoxin
Cry1C Domain III Can Function as a Specificity Determinant for
Spodoptera exigua in Different, but Not All,
Cry1-Cry1C Hybrids
*
Corresponding author. Mailing address: Plant Research
International, P.O. Box 16, 6700 AA Wageningen, The Netherlands. Phone: 31 317 477128. Fax: 31 317 418094. E-mail:
R.A.deMaagd{at}plant.wag-ur.nl.
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