Sectors expressing the homeobox gene liguleless3 implicate a time-dependent mechanism for cell fate acquisition along the proximal-distal axis of the maize leaf

Gary J. Muehlbauer, John E. Fowler, Michael Freeling

Research output: Contribution to journalArticlepeer-review

60 Scopus citations

Abstract

The longitudinal axis of the maize leaf is composed of, in proximal to distal order, sheath, ligule, auricle and blade. The semidominant Liguleless3-O (Lg3-O) mutation disrupts leaf development at the ligular region of the leaf midrib by transforming blade to sheath. In a previous study, we showed that leaf sectors of Lg3 mutant activity are cell nonautonomous in the transverse dimension and can confer several alternative developmental fates. In our present study we identify five Lg3 sector types in the leaf: sheath-like with displaced ligule (sheath-like), sheath-like with ectopic ligule (ectopic ligule), auricle-like, macrohairless blade and wild-type blade. The acquisition of a specific sector fate depends on the timing of Lg3 expression. Early Lg3 expression results in adoption of the sheath-like phenotype at the ligule position (a proximal cell fate), whereas later Lg3 expression at the same position results in one of the more distal cell fates. Furthermore, sheath-like Lg3 sectors exhibit a graded continuum of phenotypes in the transformed blade region from the most proximal (sheath) to the most distal (wild-type blade), suggesting that cell fate acquisition is a gradual process. We propose a model for leaf cell fate acquisition based on a timing mechanism whereby cells of the leaf primordium progress through a maturation schedule of competency stages which eventually specify the cell types along the proximal to distal axis of the leaf. In addition, the lateral borders between Lg3 'on' sectors and wild-type leaf sometimes provide evidence of no spreading of the transformed phenotype. In these cases, competency stages are inherited somatically.

Original languageEnglish (US)
Pages (from-to)5097-5106
Number of pages10
JournalDevelopment
Volume124
Issue number24
StatePublished - 1997

Keywords

  • Competency
  • Homeobox gene
  • Homeodomain protein
  • Leaf development
  • Liguleless3
  • Maize
  • Maturation schedule

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