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Zusammenfassung:
Understanding how molecular mechanisms can be linked to evolution of organism form is the founding theme of “evo-devo” studies. Transcription factors, which regulate and coordinate the expression of thousands of genes during development, represent candidate of choice to address the question of how molecular evolution of a developmental regulator can result in changes in the repertoire of gene it controls and ultimately translate into morphological evolution. The plant-specific transcription factor LEAFY controls general aspects of the life cycle in a basal plant, the moss Physcomitrella patens. In contrast, LEAFY has more specialized functions in angiosperms, where it specifically induces floral fate during the reproductive phase. This raises the question of a concomitant change in the biochemical function of LEAFY during the evolution of land plants. We have identified that the DNA binding domain of LEAFY, although largely conserved, has diverged in activity. On the contrary, other, more rapidly evolving portions of the protein have few effects on LEAFY activity 1. In a broader perspective of functional evolution of LFY among land plants, two testable hypotheses can be proposed. LFY might control similar networks of genes in non-flowering and flowering plants, with co-evolution of target sequences and LFY DNA binding specificity. Alternatively, there may have been a complete change of LFY function between basal taxa and flowering plants, in which an initial, albeit gradual change in biochemical activity was the prerequisite for recruitment and/or intercalation of new targets, such as AP1. Our results establish a framework for the study of the functional/morphological evolution of plant form and flower invention and tentative unifying scenario will be discussed.
