Evolution of Development and Physiology
Chanderbali, Andre , Altman, Naomi , Soltis, Douglas E. , Soltis, Pamela S. .
Spatial and temporal patterns in the floral transcriptome of the basal angiosperm, Persea americana (avocado): a glimpse of ancient whorls.
Flowers of the basal angiosperm, Persea americana (avocado), have two perianth whorls, three whorls of stamens, and a fourth inner whorl of staminodes, surrounding a single carpel. Apart from the increased number of androecial whorls, these flowers are structurally similar to the majority of flowering plants. However, unlike the sepals and petals typical of core-eudicots, the perianth of Persea consists of nearly identical densely pubescent greenish-yellow laminar organs, termed tepals, which are neither distinctly sepaloid nor petaloid. We used microarrays representing approximately 6200 unique avocado floral transcripts collected and sequenced by the Floral Genome Project (http://fgp.bio.psu.edu/fgp/index.html), to characterize the gene expression profiles of these floral organs, as well as whole inflorescence and floral buds, young fruit, and leaves. We identified over 2000 genes with a minimum of 2-fold differential expression in at least one of these reproductive tissues relative to leaves. To facilitate the presentation and interpretation of the transcriptional profiles captured in this large body of data, we used hierarchical clustering to group the genes and tissues on the basis of similarity in expression pattern. Genes are identified that are 1) expressed predominantly in reproductive organs, including the Persea homologs of the C-function gene, AGAMOUS; 2) expressed across all the floral whorls, but occasionally restricted to stamens, or stamens and tepals, including homologs of the E-function gene, SEPALLATA3, and the B-function genes, APETALA3 and PISTILLATA; or 3) primarily up-regulated in the tepals. The latter includes duplicate homologs of AGL6, and several additional transcription factors, indicating a more complex tepal developmental program than anticipated. Also unanticipated, but complementing the gene expression pattern, the inferred hierarchy of tissue similarity places tepals next to stamens. On the basis of these gene and tissue hierarchies, the functional components driving floral development in Persea represent a unique, and perhaps ancient, genetic program.
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Floral Genome Project
1 - University of Florida, Botany, 220 Bartram Hall, Gainesville, Florida, 32611-7800
2 - Pennsylvania State University, Statistics
3 - University of Florida, Botany
4 - University of Florida, Florida Museum of Natural History
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM