Evolução das flores: um espinho atravessado na garganta de Darwin

terça-feira, maio 19, 2009

Transcriptional signatures of ancient floral developmental genetics in avocado (Persea americana; Lauraceae)

André S. Chanderbalia,b,1, Victor A. Albertc, Jim Leebens-Mackd, Naomi S. Altmane, Douglas E. Soltisa and Pamela S. Soltisb

+Author Affiliations

aDepartment of Biology and
bFlorida Museum of Natural History, University of Florida, Gainesville, FL 32611;
cDepartment of Biological Sciences, University at Buffalo, State University of New York, Buffalo, NY 14260;
dDepartment of Plant Biology, University of Georgia, Athens, GA 30602; and
eDepartment of Statistics, Pennsylvania State University, University Park, PA 16802
Edited by M. T. Clegg, University of California, Irvine, CA, and approved February 25, 2009 (received for review November 12, 2008)


The debate on the origin and evolution of flowers has recently entered the field of developmental genetics, with focus on the design of the ancestral floral regulatory program. Flowers can differ dramatically among angiosperm lineages, but in general, male and female reproductive organs surrounded by a sterile perianth of sepals and petals constitute the basic floral structure. However, the basal angiosperm lineages exhibit spectacular diversity in the number, arrangement, and structure of floral organs, whereas the evolutionarily derived monocot and eudicot lineages share a far more uniform floral ground plan. Here we show that broadly overlapping transcriptional programs characterize the floral transcriptome of the basal angiosperm Persea americana (avocado), whereas floral gene expression domains are considerably more organ specific in the model eudicot Arabidopsis thaliana. Our findings therefore support the “fading borders” model for organ identity determination in basal angiosperm flowers and extend it from the action of regulatory genes to downstream transcriptional programs. Furthermore, the declining expression of components of the staminal transcriptome in central and peripheral regions of Persea flowers concurs with elements of a previous hypothesis for developmental regulation in a gymnosperm “floral progenitor.” Accordingly, in contrast to the canalized organ-specific regulatory apparatus of Arabidopsis, floral development may have been originally regulated by overlapping transcriptional cascades with fading gradients of influence from focal to bordering organs.

ABC model basal angiosperms comparative transcriptome analysis fading borders model floral evolution


1To whom correspondence should be addressed. E-mail: achander@botany.ufl.edu

Author contributions: A.S.C., V.A.A., J.L.-M., N.S.A., D.E.S., and P.S.S. designed research; A.S.C. performed research; A.S.C. contributed new reagents/analytic tools; A.S.C. and N.S.A. analyzed data; and A.S.C., V.A.A., J.L.-M., D.E.S., and P.S.S. wrote the paper.

The authors declare no conflict of interest.

This article is a PNAS Direct Submission.

Freely available online through the PNAS open access option.


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Fonte: Science Daily