Transgenic expression of a disease-resistance gene activated the
oxidative-stress response in rice.
Manipulated Organism:
Rice (Oryza sativa).
Inserted Transgenes:
An optimized version of the gene for cecropin A, an antimicrobial
peptide originally from the moth Hyalophora cecropia. The maize
ubiquitin promoter was used to express this gene in all parts of the
plant.
Goal of This Study:
To create rice plants resistant to the rice blast fungus Magnaporthe
grisea and to characterize the effects of transgene expression on the
rest of the genome.
Intended Effect:
Rice plants expressing cecropin A showed various degrees of resistance
to rice blast fungus in the greenhouse.
Unintended Effects:
-
Most of the transgenic plants engineered to secrete cecropin A into the
intercellular fluid (apoplast) were infertile.
-
Plants in which cecropin A was allowed to accumulate inside the cell
appeared to have normal fertility and morphology, but unintended effects
on gene expression were discovered. A fourfold increase in expression was
detected for 58 genes covering a wide range of functions.
-
In particular, three different peroxidase genes were strongly activated
in the transgenic rice plants. Peroxidase enzymes detoxify oxygen free
radicals, which are normal by-products of photosynthesis but can also
be elevated by certain stresses. When hydrogen peroxide was applied
externally to transgenic and parent rice plants, the transgenic plants
showed less signs of injury, thereby confirming high levels of peroxidase
activity.
-
Expression also increased for several genes related to protein synthesis,
folding, and secretion, most likely in response to the high expression
levels of cecropin A.
Sources:
Coca, M., G. Penas, J. Gomez, S. Campo et al. (2006). "Enhanced Resistance
to the Rice Blast Fungus Magnaporthe grisea Conferred by Expression
of a cecropin A Gene in Transgenic Rice," Planta vol. 223,
pp. 392-406.
Campo, S., S. Manrique, J. Garcia-Martinez, and B. San Segundo (2008).
"Production of Cecropin A in Transgenic Rice Plants Has an Impact on Host
Gene Expression," Plant Biotechnology Journal vol. 6, pp. 585-608.
Author Affiliations:
CSIC and IRTA, Spain.
Funding:
European Commission; Ministerio de Ciencia y Tecnologia; MEC; Generalitat
de Catalunya.
Product Status:
Not on the market as of 2009.
Copyright 2009 The Nature
Institute.
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