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Phase identity of the maize leaf is determined after leaf initiation
J A Orkwiszewski1, R S Poethig
1Plant Science Institute, Department of Biology, University of Pennsylvania, Philadelphia, PA 19104-6018, USA.
Summary
Maize shoot development involves juvenile and adult phases. Research shows leaf identity determination occurs later than previously thought, and shoot apical meristem identity doesn't initiate vegetative phase change.
Area of Science:
- Plant biology
- Developmental biology
- Genetics
Background:
- Maize shoot development transitions through juvenile and adult phases, marked by distinct leaf types.
- Phase change models predict specific timing for leaf identity determination.
Purpose of the Study:
- To investigate the precise timing of leaf type determination during maize vegetative development.
- To test existing models of phase change regulation in maize.
Main Methods:
- Clonal analysis of leaf primordia at different developmental stages.
- In vitro culture of adult shoot apices to induce rejuvenation.
- Assessment of leaf primordium size and tissue identity post-treatment.
Main Results:
- Juvenile and adult leaf regions in maize are not clonally distinct until primordia reach 700 micrometers.
- Leaf primordia up to 3 mm can be rejuvenated in vitro, with juvenile tissue distribution suggesting near-simultaneous rejuvenation.
- In vitro culture rejuvenated existing primordia but did not alter future leaf identity or total leaf number.
Conclusions:
- Leaf cell fate determination occurs later in development than previously predicted by phase change models.
- Maize leaf identity is regulated independently of shoot apical meristem identity.
- Vegetative phase change in maize is not initiated by a change in shoot apical meristem identity.