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Evolution of genetic mechanisms controlling petal and stamen development (Arabidopsis)

Posted on:2001-07-12Degree:Ph.DType:Dissertation
University:Yale UniversityCandidate:Kramer, Elena MFull Text:PDF
GTID:1460390014457181Subject:Biology
Abstract/Summary:
Our recently acquired understanding of the genetic program that controls floral organ identity in model plant species such as Arabidopsis and Antirrhinum has provided a new set of characters with which to evaluate floral evolution. In this study, I have undertaken a comparative analysis of the sequence and expression patterns of lower eudicot, magnoliid and monocot homologs of the genes which are known to control petal and stamen identity in higher eudicot model species. Analysis of the members of these paralogous gene lineages, represented by APETALA3 ( AP3) and PISTILLATA (PI) in Arabidopsis, will hopefully provide some insight into the events which shaped the evolution of petals and stamens in the angiosperms.; The cloning of AP3 and PI lineage representatives from lower eudicot, magnoliid and monocot species has revealed duplication events in both lineages. In general, the members of the PI lineage display a higher degree of sequence conservation, while the AP3 lineage appears to be in the process of diverging from a PI-like ancestor. The ancestral AP3 lineage, which I refer to as the paleoAP3 lineage, has undergone many duplication events, including one at the base of the higher eudicots which produced the euAP3 and TM6 lineages. Interestingly, the members of the euAP3 lineage, which includes the homologs of Arabidopsis AP3, are more divergent in sequence from the paleoAP3 ancestor than the TM6 representatives.; Expression analysis of these genes was performed in ten species from the lower eudicots, magnoliid dicots and monocots. These analyses have revealed that the role of AP3 and PI homologs in establishing stamen identity is conserved while their function as petal identity determinants has been much more variable. This conclusion is based on patterns of petal gene expression which are often spatially restricted and temporally dynamic, in contrast to what is observed in the higher eudicots. These results do not seem to support a model of strict conservation of the higher eudicot ABC program. They suggest either the presence of an ancestral proto-ABC program which was in the process of refinement or independent petal derivation events which have recruited the AP3/PI lineage members to novel functions.
Keywords/Search Tags:Petal, AP3, Arabidopsis, Lineage, Stamen, Evolution, Identity, Species
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