Abstract
Maintenance of undifferentiated stem cells is one of the important functions of plant apical meristems. We isolated a novel mutant, named meristem disorganization1-1 (mdo1-1), exhibiting abnormal shoot morphogenesis. The mdo1-1 homozygous plants showed pleiotrophic shoot phenotypes, such as aberrant phyllotaxis and plastochrone, and frequent stem fasciation. In the mutant shoot apical meristem, the surface cells were occasionally enlarged and canonical layer structure was disrupted, associated with elevated cell division activity. The mdo1-1 allele also affected function of root apical meristem. In the mutant root tips, quiescent center and initial cells were not maintained properly, resulting in the retarded growth of roots. Molecular cloning as well as complementation test indicated that the MDO1 gene encodes a relatively small protein found specifically in wide variety of land plants and that, in mdo1-1, tightly conserved amino acid in the orthlogs is substituted. These results, thus, suggest that the MDO1 gene function is crucial for maintenance of undifferentiated stem cells in apical meristems.
