Lax midrib1-O, a systemic, heterochronic mutant of maize

• Published in: American journal of botany Vol. 85; no. 4; pp. 481 - 491
• Main Authors: Schichnes, Denise E., Freeling, Michael
• Format: Journal Article
• Language: English
• Published: United States Botanical Soc America 01.04.1998; American Botanical Society
• Subjects: Corn; Evolutionary genetics; Genetic mutation; Genetics and Molecular Biology; heterochrony; Inbred strains; Leaves; maize; phase change; Phenotypes; Plant genetics; Plants; Poaceae; Siblings; Tassels; Zea mays
• ISSN: 0002-9122; 1537-2197
• DOI: 10.2307/2446431

Lxm1-O, a dominant EMS (ethyl methanesulfonate) induced mutation in maize (Zea mays, Poaceae), was originally reported to affect the blade/sheath boundary over the midrib region of the leaf. Here we present a more extensive analysis of the Lxm phenotype in nine different inbred lines. Lxm leaves are longer and narrower, and can initiate ectopic leaves. Additionally, Lxm1-O affects all plant organs observed. Compared to wild-type siblings, Lxm plants have fewer nodes, basal displacement of reproductive structures, and advance more quickly to the reproductive phase. We address questions as to whether Lxm1-O abbreviates a specific developmental phase, using hair, wax, and ear node data. We found that each phase was affected, although to varying degrees, depending on the inbred line. We interpret Lxm1-O to be a heterochronic mutation, causing the developmental acceleration of each phase of the shoot. Lxm1-O is novel, since other systemic heterochronic maize mutants prolong the juvenile phase, thereby extending shoot development. We discuss the importance of heterochronic mutations in the context of morphological evolution.