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.
Target 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.
Nontarget 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.
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