Project description:Several pathways conferring environmental flowering responses in Arabidopsis converge on developmental processes that mediate floral transition in the shoot apical meristem. Many characterized mutations disrupt these environmental responses, but downstream developmental processes have been more refractory to mutagenesis. We constructed a quintuple mutant impaired in several environmental pathways and showed that it possesses severely reduced flowering responses to changes in photoperiod and ambient temperature. RNA-seq analysis of the quintuple mutant showed that the expression of genes encoding gibberellin biosynthesis enzymes and transcription factors involved in the age pathway correlates with flowering. Mutagenesis of the quintuple mutant generated two late-flowering mutants, quintuple ems 1 (qem1) and qem2. The mutated genes were identified by isogenic mapping and transgenic complementation. The qem1 mutant was an allele of ga20ox2, confirming the importance of gibberellin for flowering in the absence of environmental responses. By contrast, the qem2 mutation is in CHROMATIN REMODELING 4 (CHR4), which has not been genetically implicated in floral induction. Using co-immunoprecipitation, RNA-seq and ChIP-seq, we show that CHR4 interacts with transcription factors involved in floral meristem identity and affects expression of key floral regulators. We conclude that CHR4 mediates the response to endogenous flowering pathways in the inflorescence meristem to promote floral identity.
Project description:Characterization of the activities of the transcription factor that AG encodes throughout flower development using perturbation assays and ChIP-Seq in combination with a floral induction system (FIS) that allows a stage-specific analysis of flower development. Examination of genomic regions bound by fully functional AG-GFP protein at approx floral stage 4-5 as compared to a negative control sample.
Project description:The transition from vegetative to reproductive development is one of the most important phase changes in the plant life cycle. This step is controlled by various environmental signals that are integrated at the molecular level by so-called floral integrators. One such floral integrator in Arabidopsis (Arabidopsis thaliana) is the MADS domain transcription factor SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1). Despite extensive genetic studies, little is known about the transcriptional control of SOC1, and we are just starting to explore the network of genes under the direct control of SOC1 transcription factor complexes. Here, we show that several MADS domain proteins, including SOC1 heterodimers, are able to bind SOC1 regulatory sequences. Genome-wide target gene analysis by ChIP-seq confirmed the binding of SOC1 to its own locus and shows that it also binds to a plethora of flowering-time regulatory and floral homeotic genes. In turn, the encoded floral homeotic MADS domain proteins appear to bind SOC1 regulatory sequences. Subsequent in planta analyses revealed SOC1 repression by several floral homeotic MADS domain proteins, and we show that, mechanistically, this depends on the presence of the SOC1 protein. Together, our data show that SOC1 constitutes a major hub in the regulatory networks underlying floral timing and flower development and that these networks are composed of many positive and negative autoregulatory and feedback loops. The latter seems to be crucial for the generation of a robust flower-inducing signal, followed shortly after by repression of the SOC1 floral integrator. A. thaliana SOC1 ChIP-seq w. control, 3 replicates
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.
Project description:Flower development is a dynamics process in which floral organs are produced from pools of stem cells residing in meristems (Smyth et al., 1990). In order to obtain a high resolution map of the changes of gene expression during this process thus to provide insights into specific expression patterns and their underlying gene regulatory networks, an inducible system which allows us to obtain synchronized flowers (Wellmer et al., 2006) was used to collect stage-specific floral tissues at four stages (stages 0, 2, 4 and 8) for transcriptome profiling by RNA-seq . These stages represent the status of inflorescence meristem, floral meristem specification, floral organ specification and floral organ differentiation, respectively during Arabidopsis flower development.
Project description:Characterization of the activities of the transcription factor that AG encodes throughout flower development using perturbation assays and ChIP-Seq in combination with a floral induction system (FIS) that allows a stage-specific analysis of flower development.
Project description:FUL has a dual role in regulating floral transition and fruit development. We used ChIP-seq to map and compare the FUL binding events in the two different tissues.
Project description:Poplar GeneChip was employed to detect genes expressed during the whole floral developmental process, in order to improve understanding of poplar flower development, since current knowledge on flower development was mainly from model plant Arabidopsis. Male and female floral buds of Populus tomentosa were selected at successive stages of the whole development process for RNA extraction and hybridization on Affymetrix microarrays. We sought to obtain genes contributed to floral development, but not the dynamic expression changes. To that end, equal amount of floral buds RNA per gender from different stages were mixed for the detection of expressed genes.