Project description:The transcription factors LEAFY (LFY) and APETALA1 (AP1), together with the AP1 paralog CAULIFLOWER (CAL), control the onset of flower development in a partially redundant manner. This redundancy is thought to be mediated, at least in part, through the regulation of a shared set of target genes. However, whether these genes are independently or cooperatively regulated by LFY and AP1/CAL, is currently unknown. To better understand the regulatory relationship between LFY and AP1/CAL during floral initiation, we monitored the activity of LFY in the absence of AP1/CAL function. We found that the regulation of several known LFY target genes is unaffected by AP1/CAL perturbation, while others appear to require AP1/CAL activity. Furthermore, we obtained evidence that LFY and AP1/CAL control the expression of some genes in an antagonistic manner. Notably, these include key regulators of floral initiation such TERMINAL FLOWER1 (TFL1), which had been previously reported to be directly repressed by both LFY and AP1. We show here that TFL1 expression is suppressed by AP1 but promoted by LFY. We further demonstrate that LFY has an inhibitory effect on flower formation in the absence of AP1/CAL activity. We propose that LFY and AP1/CAL may act as part of an incoherent feed-forward loop to control the establishment of a stable developmental program for the formation of flowers.
Project description:The transcription factors LEAFY (LFY) and APETALA1 (AP1)_together with the AP1 paralog CAULIFLOWER (CAL)_control the onRep_of flower development in a partially redundant manner. This redundancy is thought to be mediated_at least in part_through the regulation of a shared Rep_of target genes. However_whether these genes are independently or cooperatively regulated by LFY and AP1/CAL_is currently unknown. To better understand the regulatory relationship between LFY and AP1/CAL during floral initiation_we monitored the activity of LFY in the absence of AP1/CAL function. We found that the regulation of several known LFY target genes is unaffected by AP1/CAL perturbation_while others appear to require AP1/CAL activity. Furthermore_we obtained evidence that LFY and AP1/CAL control the expression of some genes in an antagonistic manner. Notably_these include key regulators of floral initiation such TERMINAL FLOWER1 (TFL1)_which had been previously reported to be directly repressed by both LFY and AP1. We show here that TFL1 expression is suppressed by AP1 but promoted by LFY. We further demonstrate that LFY has an inhibitory effect on flower formation in the absence of AP1/CAL activity. We propose that LFY and AP1/CAL may act as part of an incoherent feed-forward loop to control the establishment of a stable developmental program for the formation of flowers.
2017-04-28 | GSE96799 | GEO
Project description:Orchestration of floral initiation by APETALA1
Project description:The MADS-domain transcription factor APETALA1 (AP1) is a key regulator of Arabidopsis flower development. To understand the molecular mechanisms underlying AP1 function, we identified its target genes during floral initiation using a combination of gene expression profiling and genome-wide binding studies. Many of its targets encode transcriptional regulators, including known floral repressors. The latter genes are down-regulated by AP1, suggesting that it initiates floral development by abrogating the inhibitory effects of these genes. While AP1 acts predominantly as a transcriptional repressor during the earliest stages of flower development, regulatory genes known to be required for floral organ formation were found to be activated by AP1 at more advanced stages, indicating a dynamic mode of action. Our results further imply that AP1 orchestrates floral initiation by integrating growth, patterning and hormonal pathways.
Project description:Although the pattern of lateral organ formation from apical meristems establishes species-specific plant architecture, the positional information that confers cell fate to cells as they transit to the meristem flanks where they differentiate, remains largely unknown. We have combined fluorescence-activated cell sorting and RNA-seq to characterise the cell-type-specific transcriptome at the earliest developmental time-point of lateral organ formation using DORNRÖSCHEN-LIKE::GFP to mark founder-cell populations at the periphery of the inflorescence meristem (IM) in apetala1 cauliflower double mutants, which overproliferate IMs. Within these founder-cells, floral primordium identity genes are upregulated and stem-cell identity markers are downregulated. The transcriptional network of differentially expressed genes supports the hypothesis that lateral organ founder-cell specification involves the creation of polarity from the centre to the periphery of the IM and the establishment of a boundary from surrounding cells, consistent with bract initiation. In contrast to the established paradigm that sites of auxin response maxima pre-pattern lateral organ initiation in the IM, only subtle transcriptional reprogramming within the global auxin network was observed, suggesting that auxin response might play a minor role in the earliest stages of lateral floral initiation.
Project description:Description of gene expression in various types of cauliflower (including Romanesco type) Cauliflower structures develop on inflorescences from plants such as the apetala1 cauliflower double mutant in Arabidopsis thaliana or in the edible Brassica oleracea var botrytis or Romanesco. Whereas the genetic basis for the development of such structure is well understood in the model plant Arabidopsis thaliana, it is less understood in Brassica oleracea. In order to gain insight into the gene expression present in cauliflower and Romanesco curds, we performed RNA-seq analyses of mature cauliflowers and Romanesco curds and from growing cauliflowers curds. This analysis allowed to establish the nature of genes from the APETALA1 and CAULIFLOWER clade that are either mutated or expressed at very low levels in curd structures. These results shed light on the molecular nature of structures that have been selected in the domestication process.
Project description:The MADS-domain transcription factor APETALA1 (AP1) is a key regulator of Arabidopsis flower development. To understand the molecular mechanisms underlying AP1 function, we identified its target genes during floral initiation using a combination of gene expression profiling and genome-wide binding studies. Many of its targets encode transcriptional regulators, including known floral repressors. The latter genes are down-regulated by AP1, suggesting that it initiates floral development by abrogating the inhibitory effects of these genes. While AP1 acts predominantly as a transcriptional repressor during the earliest stages of flower development, regulatory genes known to be required for floral organ formation were found to be activated by AP1 at more advanced stages, indicating a dynamic mode of action. Our results further imply that AP1 orchestrates floral initiation by integrating growth, patterning and hormonal pathways. We used the AP1-GR system to conduct chromatin immunoprecipitation experiments with AP1-specific antibodies followed by deep-sequencing (ChIP-Seq) in order to determine AP1 binding sites on a genome-wide scale. Samples were generated from tissue in which the AP1-GR protein was induced for 2h using a single treatment of 1 uM DEX to the shoot apex. As control, we performed ChIP experiments using the same antibody on uninduced tissue. Experiments were done in two biological replicates.