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The role of DRNL and microRNA319a in petal and stamen growth in Arabidopsis

Posted on:2010-07-30Degree:Ph.DType:Thesis
University:Dartmouth CollegeCandidate:Nag, AnweshaFull Text:PDF
GTID:2440390002985166Subject:Biology
Abstract/Summary:
Work in Arabidopsis and other model species over the past 25 years has led to major insights into the control of floral organ identity. However, much less is known about genes that control the growth and differentiation of floral organs. In this thesis I describe the characterization of two genes, DORNROSCHEN-LIKE (DRNL) and miR319a, that play key roles in growth and differentiation of petals and stamens.;The first gene, DRNL, was identified in a genetic screen for mutants that enhanced the phenotype of the pistillata-5 (pi-5) mutant. In pi-5 drnl-2 mutants, third whorl organs are either missing or are converted to stamen filament-like organs. drnl-2 single mutants develop small filamentous organs in whorl three. I cloned DRNL via map-based approaches and it encodes an AP2 domain transcription factor. DRNL is expressed in the embryo and the seedling in the regions that exhibit high levels of active auxins. In the flower, DRNL is expressed at high levels in developing peals and stamens. Overexpression of DRNL results in severely dwarfed plants. Several lines of evidence suggest that DRNL may function in response to auxin.;The second gene, miR319a, was isolated as a genetic enhancer of drnl-2. In drnl-2 miR319a129 double mutants both second whorl petals and third whorl stamens develop as filamentous organs. miR319a129 single mutants have short narrow petals and short stamens. The best characterized miR319 targets are a subset of TCP genes: TCP2, TCP3, TCP4, TCP10 and TCP24. The mRNA levels of these TCP genes are upregulated in miR319a129. Several lines of evidence demonstrate that TCP4 is a key target of miR319a129. First, the TCP4soj6 mutant, which contains a mutation in the TCP4 miRNA binding site complementary to the miR319a129 mutation, suppresses the flower phenotype of miR319a129. Second, while expression of wild-type TCP4 under petal- and stamen-specific AP3 promoter (pAP3:TCP4) has no effect on flower development, petal and stamen development is severely disrupted when pAP3:TCP4 is present in the miR319a129 background. Overall, these results suggest that proper regulation of TCP4 by miR319a is critical in these floral organs.
Keywords/Search Tags:DRNL, TCP4, Mir319a129, Organs, Growth, Stamen
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