Genetic and molecular characterization of <italic>POLTERGEIST</italic>, a regulator of shoot meristem development in <italic>Arabidopsis thaliana</italic>.
Yu, Lita Po
2002
Abstract
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 <italic>CLAVATA</italic> loci (<italic>CLV1, CLV2</italic>, and <italic>CLV3</italic>) and <italic> WUSCHEL</italic> (<italic>WUS</italic>). I have isolated four mutant alleles of a novel locus, <italic>POLTERGEIST </italic> (<italic>POL</italic>), as suppressors of <italic>clvl, clv2</italic> and <italic>clv3</italic> phenotypes. All <italic>pol</italic> alleles were nearly indistinguishable from wild-type plants; however, <italic>pol</italic> mutations provided partial suppression of meristem defects in strong <italic> clv1</italic> and <italic>clv3</italic> alleles, and nearly complete suppression of weak <italic>clv1</italic> alleles. <italic>pol</italic> mutations partially suppressed <italic>clv1</italic> and <italic>clv2</italic> meristem defects and <italic>clv2</italic> organ development defects in an incompletely dominant fashion. <italic>pol</italic> almost completely suppressed <italic>clv2</italic> phenotypes in a recessive manner. These results suggest that <italic>POL</italic> functions downstream of <italic>CLAVATA</italic> to regulate meristem development. Dominant interactions were observed between the <italic>pol</italic> and <italic>wuschel</italic> (<italic>wus</italic>) mutations indicating that <italic> POL</italic> may function in close conjunction with <italic>WUS</italic>. Interestingly, <italic>POL</italic> expression overlaps the <italic>WUS</italic> expression domain and both proteins are predicted to be localized to the nucleus. Furthermore, <italic>pol wus</italic> flowers have significantly fewer organs than <italic>pol clv wus</italic> flowers. This result indicates that CLV has a functional role in the <italic>pol wus</italic> plants and that <italic> POL</italic> regulates both a <italic>CLV-WUS</italic> pathway and a <italic> WUS</italic>-independent <italic>CLV</italic> pathway. <italic>POL</italic> 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. <italic>POL</italic> represents a novel downstream component of the <italic> CLV</italic> shoot meristem development pathway. My genetic and molecular analyses of <italic>POL</italic> 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 <italic>CLV</italic> downstream components and the role of PP2Cs in plant development.Subjects
Arabidopsis Characterization Development Genetic Meristem Molecular Poltergeist Protein Phosphatase 2c Regulator Shoot Thaliana Wuschel
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