Proteinase inhibitor gene transfer for improving insect resistance in plants
1992
Narvaez, J. | Ryan, C.A.
Tobacco plants transformed with a tomato trypsin Inhibitor I cDNA from a wild tomato species (Lycopersicum peruvianum), under regulation by the CaMV 35S promoter, accumulated Inhibitor I proteins in leaves of about 100 µ/g tissue. When fed to Manduca sexta larvae, the leaves reduced growth of the insects by 50 percent, compared to control leaves. In similar experiments, tobacco transformed with a tomato chymotrypsin Inhibitor I gene from a modern tomato species (L. esculentum) had little effect on growth of the larvae when present in leaves at levels of over 200 µ g/g tissue. Thus the inhibitory specificities of the two Inhibitor I family members were responsible for their differential effects on the M. sexta larvae. When the CaMV 35S promoter construct-tomato chymotrypsin Inhibitor I was expressed in tomato, tobacco, nightshade, and alfalfa plants to compare levels of transgenic Inhibitor I protein accumulation in leaves of different plant species, the differences were striking. The highest accumulation of tomato Inhibitor I was in leaves of the homologous host tomato, and the lowest in the most distantly related plant, alfalfa. The synthesis of the Inhibitor I is reflected in the Inhibitor I mRNA levels, indicating that this foreign gene is transcribed at different rates in different plant species. These experiments indicate that the CaMV promoter may have limited usefulness in achieving high levels of experssion of proteinase inhibitor genes in certain crop plants, such as alfalfa
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