The Impact of Genome-Size Variation on Floral Evolution in Silene

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9726580 Meagher The evolutionary basis of flower-size variation in insect pollinated species has been an area of active interest and investigation in recent years. Results from our studies of the dioecious plant Silene latifolia suggest that specific changes in cell DNA content are related to flower-size evolution. The first major objective of this study is to determine the nature of the genetic changes associated with genome-size variation. In order to gain further insight into genetic mechanisms underlying flower size, we plan to measure the magnitude of the relationship between changes in DNA content at specific sites on chromosomes to changes in flower size. Results from this part of the study will establish the precise physical relationship between these characters. Our second objective of the proposed study is to determine the generality of this relationship between flower size and genome size by expanding our survey to include species from other sections of the genus Silene. Results from this work will help to determine the relationship between non-coding DNA and evolution of morphological characters. From a classical viewpoint, variation in morphological characters is thought to be based on variation at genetic loci that code for specific proteins. Our work is looking at morphological variation in a different way, and we aim to demonstrate that non-coding DNA is important in morphological evolution. This work also has applied implications as well. There is a growing interest in identifying quantitative trait loci (QTL) in plant and animal breeding for purposes of targeting efforts for stock improvement. An underlying assumption in such efforts is that QTL will be based on coding genes that could ultimately be manipulated through breeding or genetic engineering. Our work would suggest that QTL could in fact be based on alternative forms of DNA variation that would require different strategies for alteration and development.