ragged seedling2 (rgd2) is a novel, recessive mutation affecting lateral organ development in maize. The mutant phenotype of homozygous rgd2-R leaves is variable. Mild leaf phenotypes have a reduced midrib and may be moderately narrow and furcated; severe Rgd2-R- leaves are filamentous or even radial. Despite their radial morphology, severe Rgd2-R- mutant leaves develop distinct adaxial and abaxial anatomical features. Although Rgd2-R - mutants exhibit no reduction in adaxial or abaxial cell types, areas of epidermal cell swapping may occur that are associated with misaligned vascular bundles and outgrowths of ectopic margins. Scanning electron microscopy of young primordia and analyses of leaf developmental-marker gene expression in mutant apices reveal that RGD2 functions during recruitment of leaf founder cells and during expansive growth of leaf primordia. Overall, these phenotypes suggest that development is uncoordinated in Rgd2-R- mutant leaves, so that leaf components and tissues may develop quasi-independently. Models whereby RGD2 is required for developmental signaling during the initiation, anatomical patterning, and lateral expansion of maize leaves are discussed.
Bibliographical noteFunding Information:
The authors thank M. Freeling for assistance during early stages of this work, M. Timmermans for sharing insight and unpublished clones, J. Shields for technical assistance with Cryo-SEM microscopy, and Shane Heinen for contributions to SSR mapping. The work performed by D.H and M.S. was supported by National Science Foundation grant IBN-024959-01.
- Founder cells
- Leaf development