Developmental and Structural Section
Landis, Jacob , Baldridge, Laryssa , Hileman, Lena .
Determining the genetic basis for petal-like sepals in a close relative of snapdragon.
The majority of core eudicots perianths are differentiated into an outer protective whorl of sepals and an inner whorl of showy petals. However, undifferentiated perianths have evolved independently on numerous occasions. In the model species Antirrhinum majus (Veronicaceae) and Arabidopsis thaliana (Brassicaceae), four interacting classes of proteins are postulated to specify organ identity within the flower. According to the ABCE genetic model, A- and E-class proteins specify the identity of sepals, whereas A-, B- and E-class proteins specify the identity of petals. Unlike their close relative A. majus, flowers of Rhodochiton (Veronicaceae) species have first whorl floral organs that are showy and (at least) superficially resemble second whorl petals. We hypothesize that the first whorl organs of Rhodochiton flowers have adopted some level of petal identity, and that this is due to regulatory changes in B-class gene expression, as proposed by the modified “sliding-boundary” ABCE model. Our preliminary analyses of cell structure show similarities in cell shape between petals and petaloid sepals. However, Rhodochiton petals do not appear to possess conical cells typical of A. majus petals. To test predictions of the sliding boundary model we have isolated B-class gene orthologs in Rhodochiton and are in the process of determining their expression. B-class expression in the first and second whorls will be interpreted as evidence supporting the sliding boundary model; a hypothesis that will be further tested using virus induced gene silencing. In contrast, B-class expression exclusive to the second whorl will suggest cooption of other genes in sepaloid petal development. Some candidates include MIXTA-like genes that determine cell shape in petals of A. majus.
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1 - University of Kansas, Ecology and Evolutionary Biology, 1200 Sunnyside Avenue, Lawrence, KS, 66045, United States
2 - University of Kansas, Ecology and Evolutionary Biology, 1200 Sunnyside Ave., Lawrence, KS, 66045, USA
Presentation Type: Poster:Posters for BSA Sections
Location: Event Tent/Cliff Lodge
Date: Monday, July 27th, 2009
Time: 5:30 PM