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Analysis of Two Transcriptional Regulators that Affect Meristem Function: Arabidopsis thaliana TERMINAL FLOWER2 and Picea abies APETELA2
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Physiological Botany.
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The aerial plant body is derived from undifferentiated cells in the shoot apical meristem that in Arabidopsis thaliana is active throughout the plant life cycle. Upon transition to flowering the activity of the meristem is altered and the meristem starts to produce secondary inflorescences and floral meristems instead of leaves. Both the activity of the meristem and the decision of when to flower are processes strictly regulated by several mechanisms. In this thesis I describe the function of two genes that are active in the regulation of meristem function and in the regulation of when to shift to reproductive development.

First, the Arabidopsis gene encoding TERMINAL FLOWER2 (TFL2), homologous to HETEROCHROMATIN PROTEIN1, was isolated and characterised. Mutations in TFL2 result in plants that are dwarfed, flowers early, have reduced sensitivity to day length and terminate the inflorescence in an apical flower. As homologues from other organisms TFL2 is active in gene regulation by gene repression. I show that the gene affect flowering time by the autonomous and the photoperiod pathways, two of four floral inductive pathways. TFL2 act to repress the activity of genes that are promoters of floral meristem identity and interacts genetically with factors known to alter the chromatin state. Further tfl2 is shown to have altered levels of and response to auxin. All together this shows that TFL2 is active as a regulator of several different processes during plant development.

Second, I have characterised and studied the function of three genes encoding APETALA2 LIKE proteins in Norway spruce (Picea abies). In spruce these genes are expressed in meristems and reproductive tissues. When constitutively expressed in Arabidopsis two of the genes delays flowering time and alter the function of shoot apical and floral meristems. Together this suggests a function similar to the Arabidopsis homologues.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 2007. , p. 50
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 263
Keywords [en]
Developmental biology, Arabidopsis thaliana, Picea abies, gene regulation, development, meristem
Keywords [sv]
Utvecklingsbiologi
Identifiers
URN: urn:nbn:se:uu:diva-7437ISBN: 978-91-554-6774-1 (print)OAI: oai:DiVA.org:uu-7437DiVA, id: diva2:169525
Public defence
2007-02-02, Friessalen, Kärnhuset, EBC, Norbyvägen 14, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2007-01-11 Created: 2007-01-11 Last updated: 2009-04-02Bibliographically approved
List of papers
1. (TFL2) Regulates the Transition to Flowering Through the Autonomous Pathway
Open this publication in new window or tab >>(TFL2) Regulates the Transition to Flowering Through the Autonomous Pathway
(English)Manuscript (Other (popular science, discussion, etc.))
Identifiers
urn:nbn:se:uu:diva-95345 (URN)
Available from: 2007-01-11 Created: 2007-01-11 Last updated: 2010-01-14Bibliographically approved
2. Homeotic gene expression is regulated by TERMINAL FLOWER2 and the CAF-1 complex
Open this publication in new window or tab >>Homeotic gene expression is regulated by TERMINAL FLOWER2 and the CAF-1 complex
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(English)Manuscript (Other (popular science, discussion, etc.))
Identifiers
urn:nbn:se:uu:diva-95346 (URN)
Available from: 2007-01-11 Created: 2007-01-11 Last updated: 2010-01-14Bibliographically approved
3. TERMINAL FLOWER2 regulates auxin levels and auxin response in Arabidopsis
Open this publication in new window or tab >>TERMINAL FLOWER2 regulates auxin levels and auxin response in Arabidopsis
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(English)Manuscript (Other (popular science, discussion, etc.))
Identifiers
urn:nbn:se:uu:diva-95347 (URN)
Available from: 2007-01-11 Created: 2007-01-11 Last updated: 2010-01-14Bibliographically approved
4. APETALA2 like genes from Picea abies show functional similarities to their Arabidopsis homologues
Open this publication in new window or tab >>APETALA2 like genes from Picea abies show functional similarities to their Arabidopsis homologues
2007 (English)In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 225, no 3, p. 589-602Article in journal (Refereed) Published
Abstract [en]

In angiosperm flower development the identity of the floral organs is determined by the A, B and C factors. Here we present the characterisation of three homologues of the A class gene APETALA2 (AP2) from the conifer Picea abies (Norway spruce), Picea abies APETALA2 LIKE1 (PaAP2L1), PaAP2L2 and PaAP2L3. Similar to AP2 these genes contain sequence motifs complementary to miRNA172 that has been shown to regulate AP2 in Arabidopsis. The genes display distinct expression patterns during plant development; in the female-cone bud PaAP2L1 and PaAP2L3 are expressed in the seed-bearing ovuliferous scale in a pattern complementary to each other, and overlapping with the expression of the C class-related gene DAL2. To study the function of PaAP2L1 and PaAP2L2 the genes were expressed in Arabidopsis. The transgenic PaAP2L2 plants were stunted and flowered later than control plants. Flowers were indeterminate and produced an excess of floral organs most severely in the two inner whorls, associated with an ectopic expression of the meristem-regulating gene WUSCHEL. No homeotic changes in floral-organ identities occurred, but in the ap2-1 mutant background PaAP2L2 was able to promote petal identity, indicating that the spruce AP2 gene has the capacity to substitute for an A class gene in Arabidopsis. In spite of the long evolutionary distance between angiosperms and gymnosperms and the fact that gymnosperms lack structures homologous to sepals and petals our data supports a functional conservation of AP2 genes among the seed plants.

Keywords
APETALA2, Flowering time, Meristem maintenance, microRNA, Picea abies
National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-95348 (URN)10.1007/s00425-006-0374-1 (DOI)000243964000006 ()16953432 (PubMedID)
Available from: 2007-01-11 Created: 2007-01-11 Last updated: 2017-12-14Bibliographically approved

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