Induction of leaves directly from leaves in the maize mutant Lax midrib1-O

• Published in: Developmental biology Vol. 186; no. 1; pp. 36 - 45
• Main Authors: Schichnes, Denise, Schneeberger, Richard, Freeling, Michael
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.06.1997
• Subjects: Meristem - cytology; Meristem - growth & development; Microscopy, Electron, Scanning; Morphogenesis; Mutation; Phenotype; Plant Leaves - growth & development; Plant Leaves - ultrastructure; Zea mays - genetics
• ISSN: 0012-1606; 1095-564X
• DOI: 10.1006/dbio.1997.8579

One of the several phenes specified by the maize dominant mutation Lax midrib1-O ( Lxm1-O on 3L) is the proliferation of leaf “flaps” usually paired around veins on the abaxial leaf surface. Using histology and scanning electron microscopy, we show these flaps to be authentic leaf structures; in rare instances, complete ectopic leaves are found. The first divisions preceding flap emergence occur between plastochrons 4 and 7, stages when the course of leaf differentiation is well under way. No sign of meristem or any small, densely cytoplasmic primordium-like cells were seen at the sites of flap initiation. In addition, the sites of ectopic leaf initiation do not express KNOX ( Knotted-like h omeobo x) proteins, a molecular marker for shoot apical meristem cell identity. Thus, the cells that proliferate into ectopic leaves do not arise from a meristem or a primordium. A similar phenomenon has been described in several dicots, but in no other monocots. The details of flap morphology compared to the morphology of the leaf proper suggest a model whereby cells in regions of the leaf proper maintain the competence they acquired in the meristem. These cells then respond properly, in a regulated manner, to a delayed signal emanating from veins denoting “make the organ you are competent to make.”