Unknown,Transcriptomics,Genomics,Proteomics

Dataset Information

Orchestration of development by the bifunctional transcription factor, APETALA2

ABSTRACT: The emerging picture of transcriptional regulation is one of unexpected complexity. It is now clear that single transcription factors control hundreds, if not thousands, of direct targets by binding their genomic loci, but it is not understood how many of these are major players and how many are supporting cast. To address this, we leverage a well-characterized developmental network in Arabidopsis and map genome-wide binding of related proteins in multiple tissues. The transcription factor APETALA2 (AP2) has numerous functions, including roles in floral organ identity, seed development and stem cell maintenance. We focus on the role of AP2 in the floral transition and map direct targets on a genome-wide scale. We show that ap2 mutants flower early in long and short days, and that AP2 binds to many loci, most prominently floral pathway integrators, microRNAs and floral organ identity genes, many of which exhibit AP2-dependent transcription. Opposing, logical effects are evident in AP2 binding to two developmental microRNA genes that control AP2 expression, with AP2 positively regulating miR156 and negatively regulating miR172, forming a complex direct feedback loop, which also included all but one of the AP2-like miR172 target clade members. We also seek conserved targets by comparing the genome-wide direct target repertoire of AP2 with that of SCHLAFMÜTZE (SMZ), another member of the AP2-like miR172 target clade that shares partial redundancy, as evidenced by a hexuple mutant for the entire clade that flowered extremely early. Clear similarities and divergence are exposed in the AP2 and SMZ direct target repertoires. Finally, using an inducible expression system, we demonstrate that AP2 has dual molecular roles. It functions both as a transcriptional activator and repressor, directly inducing the expression of the floral repressor AGAMOUS-LIKE 15 (AGL15), and directly repressing the transcription of floral activators like SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1). ChIP-Seq of two biological replicates for ATH-AP2 and respective control samples

ORGANISM(S): Arabidopsis thaliana

SUBMITTER: Felix Ott

PROVIDER: E-GEOD-21301 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Publications

Orchestration of the floral transition and floral development in Arabidopsis by the bifunctional transcription factor APETALA2.

Yant Levi L Mathieu Johannes J Dinh Thanh Theresa TT Ott Felix F Lanz Christa C Wollmann Heike H Chen Xuemei X Schmid Markus M

The Plant cell 20100730 7

The Arabidopsis thaliana transcription factor APETALA2 (AP2) has numerous functions, including roles in seed development, stem cell maintenance, and specification of floral organ identity. To understand the relationship between these different roles, we mapped direct targets of AP2 on a genome-wide scale in two tissue types. We find that AP2 binds to thousands of loci in the developing flower, many of which exhibit AP2-dependent transcription. Opposing, logical effects are evident in AP2 binding ...[more]

PMID: 20675573

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Project description:The emerging picture of transcriptional regulation is one of unexpected complexity. It is now clear that single transcription factors control hundreds, if not thousands, of direct targets by binding their genomic loci, but it is not understood how many of these are major players and how many are supporting cast. To address this, we leverage a well-characterized developmental network in Arabidopsis and map genome-wide binding of related proteins in multiple tissues. The transcription factor APETALA2 (AP2) has numerous functions, including roles in floral organ identity, seed development and stem cell maintenance. We focus on the role of AP2 in the floral transition and map direct targets on a genome-wide scale. We show that ap2 mutants flower early in long and short days, and that AP2 binds to many loci, most prominently floral pathway integrators, microRNAs and floral organ identity genes, many of which exhibit AP2-dependent transcription. Opposing, logical effects are evident in AP2 binding to two developmental microRNA genes that control AP2 expression, with AP2 positively regulating miR156 and negatively regulating miR172, forming a complex direct feedback loop, which also included all but one of the AP2-like miR172 target clade members. We also seek conserved targets by comparing the genome-wide direct target repertoire of AP2 with that of SCHLAFMÜTZE (SMZ), another member of the AP2-like miR172 target clade that shares partial redundancy, as evidenced by a hexuple mutant for the entire clade that flowered extremely early. Clear similarities and divergence are exposed in the AP2 and SMZ direct target repertoires. Finally, using an inducible expression system, we demonstrate that AP2 has dual molecular roles. It functions both as a transcriptional activator and repressor, directly inducing the expression of the floral repressor AGAMOUS-LIKE 15 (AGL15), and directly repressing the transcription of floral activators like SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1).

Project description:The molecular mechanisms by which floral homeotic genes act as major developmental switches to specify the identity of floral organs, are still largely unknown. Floral homeotic genes encode transcription factors of the MADS-box family, which are supposed to assemble in a combinatorial fashion into organ-specific multimeric protein complexes. Major mediators of protein interactions are MADS-domain proteins of the SEPALLATA subfamily, which play a crucial role in the development of all types of floral organs. In order to characterize the roles of the SEPALLATA3 transcription factor complexes at the molecular level, we analyzed genome-wide the direct targets of SEPALLATA3. We used chromatin immunoprecipitation followed by ultrahigh-throughput sequencing or hybridization to whole-genome tiling arrays to obtain genome-wide DNA-binding patterns of SEPALLATA3. The results demonstrate that SEPALLATA3 binds to thousands of sites in the genome. Most potential target sites that were strongly bound in wild-type inflorescences, are also bound in the floral homeotic agamous mutant, which displays only the perianth organs, sepals and petals. Characterization of the target genes shows that SEPALLATA3 integrates and modulates different growth-related and hormonal pathways in a combinatorial fashion with other MADS-box proteins and possibly with non-MADS transcription factors. In particular, the results suggest multiple links between SEPALLATA3 and auxin signaling pathways. Our gene expression analyses link the genomic binding site data with the phenotype of plants expressing a dominant repressor version of SEPALLATA3, suggesting that it modulates auxin response to facilitate floral organ outgrowth and morphogenesis. Furthermore, the binding of the SEPALLATA3 protein to cis-regulatory elements of other MADS-box genes and expression analyses reveal that this protein is a key component in the regulatory transcriptional network underlying the formation of floral organs. ChIP experiments were performed on Arabidopsis wildtype and agamous mutant inflorescences using an antibody raised against a C-terminal peptide of SEP3. As control, ChIP experiments were performed on the sep3 mutant.

Dataset Information

Orchestration of development by the bifunctional transcription factor, APETALA2

Publications

Orchestration of the floral transition and floral development in Arabidopsis by the bifunctional transcription factor APETALA2.

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