Dataset Information

Molecular basis for the specification of floral organs by APETALA3 and PISTILLATA.

ABSTRACT: How different organs are formed from small sets of undifferentiated precursor cells is a key question in developmental biology. To understand the molecular mechanisms underlying organ specification in plants, we studied the function of the homeotic selector genes APETALA3 (AP3) and PISTILLATA (PI), which control the formation of petals and stamens during Arabidopsis flower development. To this end, we characterized the activities of the transcription factors that AP3 and PI encode throughout flower development by using perturbation assays as well as transcript profiling and genomewide localization studies, in combination with a floral induction system that allows a stage-specific analysis of flower development by genomic technologies. We discovered considerable spatial and temporal differences in the requirement for AP3/PI activity during flower formation and show that they control different sets of genes at distinct phases of flower development. The genomewide identification of target genes revealed that AP3/PI act as bifunctional transcription factors: they activate genes involved in the control of numerous developmental processes required for organogenesis and repress key regulators of carpel formation. Our results imply considerable changes in the composition and topology of the gene network controlled by AP3/PI during the course of flower development. We discuss our results in light of a model for the mechanism underlying sex-determination in seed plants, in which AP3/PI orthologues might act as a switch between the activation of male and the repression of female development.

SUBMITTER: Wuest SE

PROVIDER: S-EPMC3421202 | biostudies-literature | 2012 Aug

REPOSITORIES: biostudies-literature

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Molecular basis for the specification of floral organs by APETALA3 and PISTILLATA.

Wuest Samuel E SE O'Maoileidigh Diarmuid S DS Rae Liina L Kwasniewska Kamila K Raganelli Andrea A Hanczaryk Katarzyna K Lohan Amanda J AJ Loftus Brendan B Graciet Emmanuelle E Wellmer Frank F

Proceedings of the National Academy of Sciences of the United States of America 20120730 33

How different organs are formed from small sets of undifferentiated precursor cells is a key question in developmental biology. To understand the molecular mechanisms underlying organ specification in plants, we studied the function of the homeotic selector genes APETALA3 (AP3) and PISTILLATA (PI), which control the formation of petals and stamens during Arabidopsis flower development. To this end, we characterized the activities of the transcription factors that AP3 and PI encode throughout flo ...[more]

PMID: 22847437

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Project description:BACKGROUND AND AIMS: According to the floral ABC model, B-function genes appear to play a key role in the origin and diversification of the perianth during the evolution of angiosperms. The basal angiosperm Hedyosmum orientale (Chloranthaceae) has unisexual inflorescences associated with a seemingly primitive reproductive morphology and a reduced perianth structure in female flowers. The aim of this study was to investigate the nature of the perianth and the evolutionary state of the B-function programme in this species. METHODS: A series of experiments were conducted to characterize B-gene homologues isolated from H. orientale, including scanning electron microscopy to observe the development of floral organs, phylogenetic analysis to reconstruct gene evolutionary history, reverse transcription-PCR, quantitative real-time PCR and in situ hybridization to identify gene expression patterns, the yeast two-hybrid assay to explore protein dimerization affinities, and transgenic analyses in Arabidopsis thaliana to determine activities of the encoded proteins. KEY RESULTS: The expression of HoAP3 genes was restricted to stamens, whereas HoPI genes were broadly expressed in all floral organs. HoAP3 was able to partially restore the stamen but not petal identity in Arabidopsis ap3-3 mutants. In contrast, HoPI could rescue aspects of both stamen and petal development in Arabidopsis pi-1 mutants. When the complete C-terminal sequence of HoPI was deleted, however, no or weak transgenic phenotypes were observed and homodimerization capability was completely abolished. CONCLUSIONS: The results suggest that Hedyosmum AP3-like genes have an ancestral function in specifying male reproductive organs, and that the activity of the encoded PI-like proteins is highly conserved between Hedyosmum and Arabidopsis. Moreover, there is evidence that the C-terminal region is important for the function of HoPI. Our findings indicate that the development of the proposed perianth in Hedyosmum does not rely on the B homeotic function.

Dataset Information

Molecular basis for the specification of floral organs by APETALA3 and PISTILLATA.

Publications

Molecular basis for the specification of floral organs by APETALA3 and PISTILLATA.

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