| The shoot meristem gives rise to all the above-ground organs by maintaining a population of stem cells. The size and structure of the shoot meristem are maintained throughout development by balancing the proliferation and differentiation of these pluripotent cells. Several genes have been identified to be regulators of meristem development including the CLAVATA loci (CLV1, CLV2, and CLV3) and WUSCHEL (WUS).; I have isolated four mutant alleles of a novel locus, POLTERGEIST (POL), as suppressors of clvl, clv2 and clv3 phenotypes. All pol alleles were nearly indistinguishable from wild-type plants; however, pol mutations provided partial suppression of meristem defects in strong clv1 and clv3 alleles, and nearly complete suppression of weak clv1 alleles. pol mutations partially suppressed clv1 and clv2 meristem defects and clv2 organ development defects in an incompletely dominant fashion. pol almost completely suppressed clv2 phenotypes in a recessive manner. These results suggest that POL functions downstream of CLAVATA to regulate meristem development.; Dominant interactions were observed between the pol and wuschel (wus) mutations indicating that POL may function in close conjunction with WUS. Interestingly, POL expression overlaps the WUS expression domain and both proteins are predicted to be localized to the nucleus. Furthermore, pol wus flowers have significantly fewer organs than pol clv wus flowers. This result indicates that CLV has a functional role in the pol wus plants and that POL regulates both a CLV-WUS pathway and a WUS-independent CLV pathway.; POL encodes a protein phosphatase 2C (PP2C) with a predicted nuclear localization sequence, suggesting that it has a role in signal transduction within the nucleus. The N-terminus has possible regulatory function and the C-terminus has catalytic activity. Although the functional domains of PP2Cs are conserved, the POL protein represents a unique subclass of plant PP2Cs.; POL represents a novel downstream component of the CLV shoot meristem development pathway. My genetic and molecular analyses of POL have expanded our understanding of how stem cells are maintained at the meristem. In particular, this study provides a good foundation for future understanding of CLV downstream components and the role of PP2Cs in plant development. |
