Biomedical subjects

Monika Demar

Publications and source records attributed to Monika Demar.

3 recordsLinked to original sources

PubMed2005

WUSCHEL controls meristem function by direct regulation of cytokinin-inducible response regulators.

Plants continuously maintain pools of totipotent stem cells in their apical meristems from which elaborate root and shoot systems are produced. In Arabidopsis thaliana, stem cell fate in the shoot apical meristem is controlled by a regulatory network that includes the CLAVATA (CLV) ligand-receptor system and the homeodomain protein WUSCHEL (WUS). Phytohormones such as auxin and cytokinin are also important for meristem regulation. Here we show a mechanistic link between the CLV/WUS network and hormonal control. WUS, a positive regulator of stem cells, directly represses the transcription of several two-component ARABIDOPSIS RESPONSE REGULATOR genes (ARR5, ARR6, ARR7 and ARR15), which act in the negative-feedback loop of cytokinin signalling. These data indicate that ARR genes might negatively influence meristem size and that their repression by WUS might be necessary for proper meristem function. Consistent with this hypothesis is our observation that a mutant ARR7 allele, which mimics the active, phosphorylated form, causes the formation of aberrant shoot apical meristems. Conversely, a loss-of-function mutation in a maize ARR homologue was recently shown to cause enlarged meristems.

Arabidopsis↗

PubMed2005

A gene expression map of Arabidopsis thaliana development.

Regulatory regions of plant genes tend to be more compact than those of animal genes, but the complement of transcription factors encoded in plant genomes is as large or larger than that found in those of animals. Plants therefore provide an opportunity to study how transcriptional programs control multicellular development. We analyzed global gene expression during development of the reference plant Arabidopsis thaliana in samples covering many stages, from embryogenesis to senescence, and diverse organs. Here, we provide a first analysis of this data set, which is part of the AtGenExpress expression atlas. We observed that the expression levels of transcription factor genes and signal transduction components are similar to those of metabolic genes. Examining the expression patterns of large gene families, we found that they are often more similar than would be expected by chance, indicating that many gene families have been co-opted for specific developmental processes.

Arabidopsis↗

PubMed2003

Dissection of floral induction pathways using global expression analysis.

Flowering of the reference plant Arabidopsis thaliana is controlled by several signaling pathways, which converge on a small set of genes that function as pathway integrators. We have analyzed the genomic response to one type of floral inductive signal, photoperiod, to dissect the function of several genes transducing this stimulus, including CONSTANS, thought to be the major output of the photoperiod pathway. Comparing the effects of CONSTANS with those of FLOWERING LOCUS T, which integrates inputs from CONSTANS and other floral inductive pathways, we find that expression profiles of shoot apices from plants with mutations in either gene are very similar. In contrast, a mutation in LEAFY, which also acts downstream of CONSTANS, has much more limited effects. Another pathway integrator, SUPPRESSOR OF OVEREXPRESSION OF CO 1, is responsive to acute induction by photoperiod even in the presence of the floral repressor encoded by FLOWERING LOCUS C. We have discovered a large group of potential floral repressors that are down-regulated upon photoperiodic induction. These include two AP2 domain-encoding genes that can repress flowering. The two paralogous genes, SCHLAFMUTZE and SCHNARCHZAPFEN, share a signature with partial complementarity to the miR172 microRNA, whose precursor we show to be induced upon flowering. These and related findings on SPL genes suggest that microRNAs play an important role in the regulation of flowering.

Animals↗