A protodermal miR394 signal defines a region of stem cell competence in the Arabidopsis shoot meristem
Zusammenfassung der Projektergebnisse
In this project, we investigate a central question of stem cell maintenance: how is the architecture of the stem cell niche stable reproduced in spite of the ongoing cell divisions of the stem cells and their progeny? In the shoot meristem of higher plants, the stem cells are located in the three outermost cell layers of the shoot tip. Underneath the stem cells is located the organizing center, a small group of cells providing signals to the stem cells to maintain their undifferentiated state. We previously found that maintenance of shoot meristem stem cells during embryo development requires a mobile micro RNA molecule, miR394, which is expressed exclusively in the outmost protodermal layer of the shoot meristem but can move into the next two underlying cell layers. miR394 provides stem cell competence to the cell in the shoot tip by enabling them to respond to the transcription factor WUS. It does do so by targeting the miRNA of LCR, an F-Box protein, towards decay. In this project, we firstly show that miR394 is required to maintain stem cells throughout postembryonic development. We also demonstrate that miR394 expression can convert differentiated cells into shoot meristem stem cells and, unexpectedly, that it can promote the formation of somatic embryos, which is an important tool in agricultural propagation of plants with a desired genotype. At the base of the role of miR394 in patterning the stem cell niche lies its specific expression. Unexpectedly we found that this expression is independent of known regulators of epidermal cell specification, suggesting a novel fundamental patterning mechanism that separate epidermal from inner cells in the embryo. We have identified the important regulatory sequences in the MIR394B gene and we have started to search for transcription factors that bind to these sequences. Finally, we employed several approaches to isolate the target protein(s) recognized by the F-Box protein LCR, as a readout of miR394 signaling in stem cell regulation. We have isolated a homolog of an animal oncogene as potential target, which will be further investigated.
Projektbezogene Publikationen (Auswahl)
- (2020). Integration of pluripotency pathways regulates stem cell maintenance in the Arabidopsis shoot meristem. Proc Natl Acad Sci USA 117, 22561-22571
Su, Y.H., Zhou, C., Li, Y.J., Yu, Y., Tang, L.P., Zhang, W.J., Yao, W.J., Huang, R., Laux, T., and Zhang, X.S.
(Siehe online unter https://doi.org/10.1073/pnas.2015248117)
