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Unintended Effects of Genetic Manipulation
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Spring wheat with scab-resistance transgene was not scab-resistant and showed localized death of leaf tissue.

Manipulated Organism: Spring wheat (Triticum aestivum L.), cultivar Bobwhite.

Inserted Transgenes: PR-2 and PR-3 genes for the pathogenesis-related proteins, beta-1,3-glucanase and chitinase, respectively, derived from the scab-resistant wheat cultivar Sumai-3. The genes were fused to the maize ubiquitin promoter so that they would be expressed in all parts of the plant.

Goal: Make spring wheat resistant to scab (Fusarium, head blight), a major disease.

Intended Effect: Four of the twenty-four transgenic lines expressed either one or both of the transgenes; these four lines showed stable inheritance of the transgenes for up to four generations; one line (32A) showed reduced scab infection under greenhouse conditions.

Unintended Effects:
  • Transgene activity in twenty of the twenty-four transgenic lines (80%) shut down after the initial generation, apparently due to gene silencing.
  • None of the plants from the four transgene-expressing lines was resistant to scab infection under field conditions (including plants of Line 32A that showed reduced scab infection under greenhouse conditions).
  • Plants of Line 32A, which had the highest transgene expression, also suffered from a "lesion-mimic phenotype" in which the leaves developed necrotic (tissue death) spots during flower formation (booting).

Source: Anand, A., T. Zhou, H. N. Trick, B. S. Gill et al. (2003). "Greenhouse and Field Testing of Transgenic Wheat Plants Stably Expressing Genes for Thaumatin-like Protein, Chitinase and Glucanase against Fusarium graminearum," Journal of Experimental Biology vol. 54, pp. 1101-11.

Author Affiliations: Departments of Biochemistry and Plant Pathology, Kansas State University.

Funding: Kansas Wheat Commission and the U.S. Wheat and Barley Scab Initiative (partial).

Product Status: Not on the market as of 2008.

Copyright 2008 The Nature Institute.

This document: http://natureinstitute.org/nontarget/reports/wheat_003.php

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