@phdthesis{Schumacher2019,
  author    = {Schumacher, Julia},
  title     = {Regulation and function of STERILE APETALA in Arabidopsis flower development},
  school      = {Universit{\"a}t Potsdam},
  pages     = {144},
  year      = {2019},
  abstract  = {STERILE APETALA (SAP) is known to be an essential regulator of flower development for over 20 years. Loss of SAP function in the model plant Arabidopsis thaliana is associated with a reduction of floral organ number, size and fertility. In accordance with the function of SAP during early flower development, its spatial expression in flowers is confined to meristematic stages and to developing ovules. However, to date, despite extensive research, the molecular function of SAP and the regulation of its spatio-temporal expression still remain elusive. In this work, amino acid sequence analysis and homology modeling revealed that SAP belongs to the rare class of plant F-box proteins with C-terminal WD40 repeats. In opisthokonts, this type of F-box proteins constitutes the substrate binding subunit of SCF complexes, which catalyze the ubiquitination of proteins to initiate their proteasomal degradation. With LC-MS/MS-based protein complex isolation, the interaction of SAP with major SCF complex subunits was confirmed. Additionally, candidate substrate proteins, such as the growth repressor PEAPOD 1 and 2 (PPD1/2), could be revealed during early stages of flower development. Also INDOLE-3-BUTYRIC ACID RESPONSE 5 (IBR5) was identified among putative interactors. Genetic analyses indicated that, different from substrate proteins, IBR5 is required for SAP function. Protein complex isolation together with transcriptome profiling emphasized that the SCFSAP complex integrates multiple biological processes, such as proliferative growth, vascular development, hormonal signaling and reproduction. Phenotypic analysis of sap mutant and SAP overexpressing plants positively correlated SAP function with plant growth during reproductive and vegetative development. Furthermore, to elaborate on the transcriptional regulation of SAP, publicly available ChIP-seq data of key floral homeotic proteins were reanalyzed. Here, it was shown that the MADS-domain transcription factors APETALA 1 (AP1), APETALA 3 (AP3), PISTILLATA (PI), AGAMOUS (AG) and SEPALLATA 3 (SEP3) bind to the SAP locus, which indicates that SAP is expressed in a floral organ-specific manner. Reporter gene analyses in combination with CRISPR/Cas9-mediated deletion of putative regulatory regions further demonstrated that the intron contains major regulatory elements of SAP in Arabidopsis thaliana. In conclusion, these data indicate that SAP is a pleiotropic developmental regulator that acts through tissue-specific destabilization of proteins. The presumed transcriptional regulation of SAP by the floral MADS-domain transcription factors could provide a missing link between the specification of floral organ identity and floral organ growth pathways.},
  language  = {en}
}
@misc{PajoroMadrigalMuinoetal.2014,
  author    = {Pajoro, Alice and Madrigal, Pedro and Mui{\~n}o, Jose M. and Matus, Jos{\´e} Tom{\´a}s and Jin, Jian and Mecchia, Martin A. and Debernardi, Juan M. and Palatnik, Javier F. and Balazadeh, Salma and Arif, Muhammad and {\´O}'Maoil{\´e}idigh, Diarmuid S. and Wellmer, Frank and Krajewski, Pawel and Riechmann, Jos{\´e}-Luis and Angenent, Gerco C. and Kaufmann, Kerstin},
  title     = {Dynamics of chromatin accessibility and gene regulation by MADS-domain transcription factors in flower development},
  series = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  volume    = {15},
  journal   = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-43113},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-431139},
  pages     = {19},
  year      = {2014},
  abstract  = {Background: Development of eukaryotic organisms is controlled by transcription factors that trigger specific and global changes in gene expression programs. In plants, MADS-domain transcription factors act as master regulators of developmental switches and organ specification. However, the mechanisms by which these factors dynamically regulate the expression of their target genes at different developmental stages are still poorly understood. Results: We characterized the relationship of chromatin accessibility, gene expression, and DNA binding of two MADS-domain proteins at different stages of Arabidopsis flower development. Dynamic changes in APETALA1 and SEPALLATA3 DNA binding correlated with changes in gene expression, and many of the target genes could be associated with the developmental stage in which they are transcriptionally controlled. We also observe dynamic changes in chromatin accessibility during flower development. Remarkably, DNA binding of APETALA1 and SEPALLATA3 is largely independent of the accessibility status of their binding regions and it can precede increases in DNA accessibility. These results suggest that APETALA1 and SEPALLATA3 may modulate chromatin accessibility, thereby facilitating access of other transcriptional regulators to their target genes. Conclusions: Our findings indicate that different homeotic factors regulate partly overlapping, yet also distinctive sets of target genes in a partly stage-specific fashion. By combining the information from DNA-binding and gene expression data, we are able to propose models of stage-specific regulatory interactions, thereby addressing dynamics of regulatory networks throughout flower development. Furthermore, MADS-domain TFs may regulate gene expression by alternative strategies, one of which is modulation of chromatin accessibility.},
  language  = {en}
}
@article{OmidbakhshfardProostFujikuraetal.2015,
  author    = {Omidbakhshfard, Mohammad Amin and Proost, Sebastian and Fujikura, Ushio and M{\"u}ller-R{\"o}ber, Bernd},
  title     = {Growth-Regulating Factors (GRFs): A Small Transcription Factor Family with Important Functions in Plant Biology},
  series = {Molecular plant},
  volume    = {8},
  journal   = {Molecular plant},
  number    = {7},
  publisher = {Cell Press},
  address   = {Cambridge},
  issn      = {1674-2052},
  doi       = {10.1016/j.molp.2015.01.013},
  pages     = {998 -- 1010},
  year      = {2015},
  abstract  = {Growth-regulating factors (GRFs) are plant-specific transcription factors that were originally identified for their roles in stem and leaf development, but recent studies highlight them to be similarly important for other central developmental processes including flower and seed formation, root development, and the coordination of growth processes under adverse environmental conditions. The expression of several GRFs is controlled by microRNA miR396, and the GRF-miRNA396 regulatory module appears to be central to several of these processes. In addition, transcription factors upstream of GRFs and miR396 have been discovered, and gradually downstream target genes of GRFs are being unraveled. Here, we review the current knowledge of the biological functions performed by GRFs and survey available molecular data to illustrate how they exert their roles at the cellular level.},
  language  = {en}
}
@article{AbdirashidLenhard2020,
  author    = {Abdirashid, Hashim and Lenhard, Michael},
  title     = {Say it with double flowers},
  series = {Journal of experimental botany},
  volume    = {71},
  journal   = {Journal of experimental botany},
  number    = {9},
  publisher = {Oxford Univ. Press},
  address   = {Oxford},
  issn      = {0022-0957},
  doi       = {10.1093/jxb/eraa109},
  pages     = {2469 -- 2471},
  year      = {2020},
  abstract  = {Every year, lovers world-wide rely on mutants to show their feelings on Valentine's Day. This is because many of the most popular ornamental flowering plants have been selected to form extra petals at the expense of reproductive organs to enhance their attractiveness and aesthetic value to humans. This so-called 'double flower' (DF) phenotype, first described more than 2000 years ago (Meyerowitz et al., 1989) is present, for example, in many modern roses, carnations, peonies, and camellias. Gattolin et al. (2020) now identify a unifying explanation for the molecular basis of many of these DF cultivars.},
  language  = {en}
}