Plant development and evolution: Lessons learned from candidate genes
Kuzoff, Robert , Cho, Eun Young , Du, Meizhu , Li, Wenli .
Unraveling the molecular-genetic basis of ovule shape disparities among angiosperms.
Angiosperm ovules are an excellent system with which to explore the developmental basis of morphological innovations. Over the history of flowering plant evolution structural disparities have arisen among angiosperm ovules in terms of the number of integuments they have and the orientation of their micropyles. Transitions from bitegmy to unitegmy have occurred at least seven times and there have been at least twelve transitions between anatropy and orthotropy. Structural homology studies suggest that unitegmy arises through a phylogenetic fusion of outer and inner integuments in some lineages and a loss of one integument in others. Comparative studies among angiosperm ovules and mutational analysis in Arabidopsis both indicate that there is a tight and perhaps causal link between the mode of outer integument growth and the orientation of the ovule. Hence, understanding the functional evolution of genes regulating outer integument development may help to explain transitions in two key aspects of ovule diversification; integument number and ovule orientation. We hypothesize that shape disparities of this variety result from changes in the function of genes regulating ovule development. Candidate genes include orthologs of INNER NO OUTER (INO), a single copy gene that has been rigorously characterized in Arabidopsis, and two of its negative regulators, SUPERMAN and NOZZLE. We have cloned orthologs of these genes from a broad range angiosperms and begun exploring the natural history of the gene families to which they belong. Comparative gene expression studies reveal functional conservation among INO orthologs at the transcriptional level, but transormation of INO orthologs into Arabidiosis mutants clearly reveals functional divergence among encoded proteins. Ongoing studies seek to clarify the relationship between molecular evolution in these ovule regulatory genes and the diversification of angiosperm ovule form.
1 - University of Georgia, Department of Plant Biology, 2502 Plant Sciences, Athens, Georgia, 30602-7271, U.S.A.
INNER NO OUTER
Presentation Type: Symposium
Location: Ballroom 1 (Cliff Lodge)
Date: Wednesday, August 4th, 2004
Time: 11:00 AM