The Role of LEAFY in the Evolution of Rosette-Flowering

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0078161Baum Plant species differ in the manner in which they bear their flowers. The aim of this work is to elucidate how such differences might arise through the modification of gene activity and function. The strategy is to compare the genetic model system, Arabidopsis thaliana, with some wild relatives (Jonopsidium acaule, Leavenworthia alabamica and Idahoa scapigera) that differ in the manner in which flowers are produced. Whereas Arabidopsis produces flowers on an elongated, leafless inflorescence, the other three are "rosette-flowering," producing flowering from the axils of rosette leaves. Phylogenetic data show that rosette-flowering evolved three times independently from inflorescence-flowering ancestors. Based on information from Arabidopsis and prior work on Jonopsidium it is likely that the difference in flower production reflects changes in the regulation of the flower meristem identity gene, LEAFY (LFY). The aim of this study is to test this hypothesis by (1) characterizing LFY expression in Idahoa and Leavenworthia and (2) by cloning LFY homologs (with intact promoters) from the rosette-flowering taxa and the introducing those genes into Arabidopsis. If Arabidopsis plants containing exogenous LFY show modified LFY expression this will suggest evolution in the LFY promoter. Additionally, If transgenes cause partial or complete conversion to rosette-flowering the most likely explanation is that changes at the LFY locus contributed to the evolution of rosette-flowering. The study will, therefore, shed light on the role of LFY in the evolution of flowering morphology, and will serve to clarify a general approach that can be used to study the genetic basis of morphological and developmental evolution