Lateral root formation is an important determinant of root system architecture. In Arabidopsis, lateral roots originate from pericycle cells, which undergo a program of morphogenesis to generate a new lateral root meristem. Despite its importance for root meristem organization, the onset of quiescent center (QC) formation during lateral root morphogenesis remains unclear. Here, we used live 3D confocal imaging to monitor cell organization and identity acquisition during lateral root development. Our dynamic observations revealed an early morphogenesis phase and a late meristem formation phase as proposed in the bi-phasic growth model. Establishment of lateral root QCs coincided with this developmental phase transition. QC precursor cells originated from the outer layer of stage II lateral root primordia, within which the SCARECROW (SCR) transcription factor was specifically expressed. Disrupting SCR function abolished periclinal divisions in this lateral root primordia cell layer and perturbed the formation of QC precursor cells. We conclude that de novo QC establishment in lateral root primordia operates via SCR-mediated formative cell division and coincides with the developmental phase transition.
The authors declare no competing or financial interests.
T.G., L.L., M.J.B. and S.G. designed the research; T.G. and K.S. performed the research; T.G., K.T., D.M.W., M.Y., T.M., D.W., H.F. and S.G. contributed new tools; T.G., L.L., M.J.B. and S.G. analyzed the data; T.G., K.T., H.F., L.L., M.J.B. and S.G. wrote the paper; all authors read and approved the paper.
This work was supported by the Ministry of Education, Culture, Sports, Science, and Technology (MEXT) through a JSPS Research Fellowship for Young Scientists [12J02079 to T.G.]; a Grant-in-Aid for Scientific Research on Priority Areas [19060006 to H.F.]; and a Grant-in-Aid for Scientific Research on Innovative Areas [25113003 to H.F.].
Supplementary information available online at http://dev.biologists.org/lookup/doi/10.1242/dev.135319.supplemental
- Received January 15, 2016.
- Accepted July 26, 2016.