Mutations in Two Independent Genes Lead to Suppression of the Shoot Apical Meristem in Maize

• Published in: Plant physiology (Bethesda) 2002-02, Vol.128 (2), p.502-511
• Main Authors: Roberto Pilu, Gabriella Consonni, Elena Busti, Andrew P. Mac Cabe, Anna Giulini, Dolfini, Silvana, Giuseppe Gavazzi
• Format: Article
• Language: English
• Subjects: Adenine - analogs & derivatives; Adenine - physiology; Agronomy. Soil science and plant productions; Apical meristems; Biological and medical sciences; Chromosome Mapping; Coleoptiles; Corn; Cytokinins - physiology; Development and Hormone Action; dgr gene; Economic plant physiology; Embryonic growth stage; Embryos; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Plant; Genes, Plant - genetics; Genetic mutation; Growth and development; Homeodomain Proteins - genetics; Homeodomain Proteins - metabolism; Hormones; Kinetin; Meristem - genetics; Meristem - growth & development; Meristems; Morphogenesis, differentiation, rhizogenesis, tuberization. Senescence; Mutants; Mutation; Phenotype; Phenotypes; Plant growth. Development of the storage organs; Plant physiology and development; Plant Proteins - genetics; Plant Shoots - genetics; Plant Shoots - growth & development; Plants; Seedlings; Segregation; Signal Transduction - physiology; sml gene; Vegetative apparatus, growth and morphogenesis. Senescence; Zea mays; Zea mays - genetics; Zea mays - growth & development
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.010767

The shoot apical meristem (SAM), initially formed during embryogenesis, gives rise to the aboveground portion of the maize (Zea mays) plant. The shootless phenotype (sm1) described here is caused by disruption of SAM formation due to the synergistic interaction of mutations at two genetic loci. Seedlings must be homozygous for both sm1 (shootmeristemless), and the unlinked dgr (distorted growth) loci for a SAM-less phenotype to occur. Seedlings mutant only for sm1 are impaired in their morphogenesis to different extents, whereas the dgr mutation alone does not have a recognisable phenotype. Thus, dgr can be envisaged as being a dominant modifier of sm1 and the 12 (normal):3 (distorted growth):1 (shoot meristemless) segregation observed in the F2 of the double heterozygote is the result of the interaction between the sm1 and dgr genes. Other segregation patterns were also observed in the F2, suggesting instability of the dgr gene. Efforts to rescue mutant embryos by growth on media enriched with hormones have been unsuccessful so far. However, mutant roots grow normally on medium supplemented with kinetin at a concentration that suppresses wild-type root elongation, suggesting possible involvement of the mutant in the reception or transduction of the kinetin signal or transport of the hormone. The shootless mutant appears to be a valuable tool with which to investigate the organization of the shoot meristem in monocots as well as a means to assay the origins and relationships between organs such as the scutellum, the coleoptile, and leaves that are initiated during the embryogenic process.