|Tonks, Dennis - UNIVERSITY OF IDAHO|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 3, 2002
Publication Date: January 1, 2003
Interpretive Summary: Transgenes are genes added, without the use of sexual hybridization, using genetic engineering technologies. Some transgenes are not stable and as a result are not expressed in succeeding generations. More basic information about incorporation of transgenes may help solve these problems. Although several transgenic cultivars have been developed, the most efficient development, description, and use of future transgenic cultivars will be aided by a thorough understanding of the inheritance and expression (function) of transgenes. This is especially true for barley, a species for which genetic engineering has only recently been possible, because little is known about the characteristics of transgenic barley. This study was conducted to examine the behavior of transgenes over a number of generations in a large number of transgenic barley plants. The results indicated that often transgenes fail to be passed on to successive generations, and transgenes that are passed on to successive generations sometimes are not expressed and therefore cannot perform their desired function. Often several generations had to be examined to identify transgenic plants in which the transgene functioned properly; once such identification was made, however, future transgenic generations also were seen to perform properly. These results suggest that more time spent examining early generations, and on efforts to identify transgenic plants in which the transgene behavior is proper and predictable, would be beneficial. Basic information on transgene behavior will lead to efficient methods for identifying useful transgenic barley plants, and such information will reduce unpredictable behavior in transgenic plants.
Technical Abstract: Empirical assessments of transgene inheritance and expression provide data necessary for developing efficient breeding strategies for transgenic germplasm, and for guiding research into the improvement of transformation techniques. Transgene inheritance and expression (of herbicide resistance) were studied in the T1 and T3 generations of barley lines derived from 12 independent transformation events; significant deviations from expectations were observed. The primary finding was of poor transgene transmission to progeny; transgene silencing was also detected. Several transgenic lines that exhibited relatively stable transgene inheritance and expression patterns were used as parents to produce single cross and backcross-derived populations. The inheritance and expression patterns in progeny of these crosses generally fit Mendelian expectations for single, dominant loci, with some exceptions. Variability of transgene expression among progeny from the same transformation event was detected in these studies. The relative levels of herbicide resistance among progeny populations was similar to the levels of resistance exhibited by the transgenic parents of those populations. It is concluded that the level of transgene instability observed among these materials will have significant consequences on the use of such materials in breeding programs, and that improved transformation systems that facilitate transgene stability should be developed.