Person: Gleason, Emily
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Gleason
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Emily
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Gleason, Emily
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Publication Characterization of Aquilegia Polycomb Repressive Complex 2 homologs reveals absence of imprinting(Elsevier BV, 2012) Gleason, Emily; Kramer, ElenaEpigenetic regulation is important for maintaining gene expression patterns in multicellular organisms. The Polycomb Group (PcG) proteins form several complexes with important and deeply conserved epigenetic functions in both the plant and animal kingdoms. The plant Polycomb Repressive Complex 2 (PRC2) contains four core proteins, Enhancer of Zeste (E(z)), Suppressor of Zeste 12 (Su(z)12), Extra Sex Combs (ESC), and Multicopy Suppressor of IRA 1 (MSI1), and functions in many developmental transitions. In some plant species, including rice and Arabidopsis, duplications in the core PRC2 proteins allow the formation of PRC2s with distinct developmental functions. In addition, members of the plant specific VEL PHD family have been shown to associate with the PRC2 complex in Arabidopsis and may play a role in targeting the PRC2 to specific loci. Here we examine the evolution and expression of the PRC2 and VEL PHD families in Aquilegia, a member of the lower eudicot order anunculales and an emerging model for the investigation of plant ecology, evolution and developmental genetics. We find that Aquilegia has a relatively simple PRC2 with only one homolog of Su(z)12, ESC and MSI1 and two ancient copies of E(z), AqSWN and AqCLF. Aquilegia has four members of the VEL PHD family, three of which appear to be closely related to Arabidopsis proteins known to associate with the PRC2. The PRC2 and VEL PHD family proteins are expressed at a relatively constant level throughout Aquilegia vulgaris development, with the VEL PHD family and MSI1 expressed at higher levels during and after vernalization and in the inflorescence. Both AqSWN and AqCLF are expressed in Aquilegia endosperm but neither copy is imprinted.Publication Conserved Roles for Polycomb Repressive Complex 2 in the Regulation of Lateral Organ Development in Aquilegia X Coerulea 'Origami'(Springer (Biomed Central Ltd.), 2013) Gleason, Emily; Kramer, ElenaBackground: Epigenetic regulation is necessary for maintaining gene expression patterns in multicellular organisms. The Polycomb Group (PcG) proteins form several complexes with important and deeply conserved epigenetic functions in both the plant and animal kingdoms. One such complex, the Polycomb Repressive Complex 2 (PRC2), is critical to many developmental processes in plants including the regulation of major developmental transitions. In addition, PRC2 restricts the expression domain of various transcription factor families in Arabidopsis, including the class I KNOX genes and several of the ABCE class MADS box genes. While the functions of these transcription factors are known to be deeply conserved, whether or not their regulation by PRC2 is similarly conserved remains an open question. Results: Here we use virus-induced gene silencing (VIGS) to characterize the function of the PRC2 complex in lateral organ development of Aquilegia x coerulea 'Origami', a member of the lower eudicot order Ranunculales. Leaves with PRC2 down-regulation displayed a range of phenotypes including ruffled or curled laminae, additional lobing, and an increased frequency of higher order branching. Sepals and petals were also affected, being narrowed, distorted, or, in the case of the sepals, exhibiting partial homeotic transformation. Many of the petal limbs also had a particularly intense yellow coloration due to an accumulation of carotenoid pigments. We show that the A. x coerulea floral MADS box genes AGAMOUS1 (AqAG1), APETALA3-3 (AqAP3-3) and SEPALLATA3 (AqSEP3) are up-regulated in many tissues, while expression of the class I KNOX genes and several candidate genes involved in carotenoid production or degradation are largely unaffected. Conclusions: PRC2 targeting of several floral MADS box genes may be conserved in dicots, but other known targets do not appear to be. In the case of the type I KNOX genes, this may reflect a regulatory shift associated with the evolution of compound leaves.Publication Conserved Genetic Modules Controlling Lateral Organ Development: Polycomb Repressive Complex 2 and ASYMMETRIC LEAVES1 Homologs in the Lower Eudicot Aquilegia (Columbine).(2013-09-18) Gleason, Emily; Kramer, Elena M.; Bomblies, Kirsten; Extavour, CassandraDevelopment in multicellular organisms relies on establishing and maintaining gene expression profiles that give cells identity. Transcription factors establish gene expression profiles by integrating positional, temporal, and environmental cues to regulate genes essential for a cell's identity. These signals are often short lived while the differentiated state may persist for a long time. Epigenetic factors maintain these gene expression profiles by making heritable chemical alterations to target gene chromatin to stabilize transcriptional patterns. Here we explore the evolution and function of an epigenetic regulator, the Polycomb Repressive Complex 2 (PRC2), and a transcription factor, ASYMMETRIC LEAVES 1 (AS1) , in the lower eudicot Aquilegia. PRC2 is an important and deeply conserved epigenetic regulator, which is critical to many plant developmental processes, including the regulation of major developmental transitions and lateral organ development. We find that Aquilegia has a relatively simple complement of PRC2 genes that are expressed throughout development. Contrary to findings in other plant species, two members of the Aquilegia PRC2, AqSWN and AqCLF, are not imprinted in Aquilegia endosperm. Using virusinduced gene silencing (VIGS), we determined that Aquilegia PRC2 regulates aspects of lateral organ development, including branching within the leaf and lamina expansion, along with caroteinoid production in floral organs. PRC2 targeting of several floral MADS box genes may be conserved in Aquilegia, but other known targets such as the class I KNOX gene are not. AS1 is a transcription factor that plays a conserved role in controlling differentiation and polarity of lateral organs. In species with simple leaves, AS1 promotes cell determination by suppressing the expression of the class I KNOX genes in leaf primordia and regulates abaxial-adaxial polarity in the developing leaf. However, in species with compound leaves, KNOX genes and AS1 often work together to control leaflet initiation and arrangement. In Aquilegia, AqAS1 appears to primarily contribute to proper regulation of class I KNOX genes with a more minor role in leaflet polarity and positioning. Most interestingly, these combined datasets suggest that contrary to the widely held model, class I KNOX genes are neither necessary nor sufficient for leaf complexity in Aquilegia.