Neocentromere-mediated chromosome movement in maize

Area of Science:

• * Cell Biology
• * Genetics
• * Molecular Biology

Background:

• * Neocentromere activity represents a unique form of nonkinetochore chromosome movement.
• * In maize, the Abnormal chromosome 10 (Ab10) gene induces neocentromeres, causing heterochromatic knobs to move towards the spindle poles during meiotic anaphase.

Purpose of the Study:

• * To investigate how neocentromere activity impacts the function of linked centromere/kinetochores.
• * To determine if neocentromeres and kinetochores are mobilized by the same spindle mechanism.
• * To elucidate the mechanism driving neocentromere motility.

Main Methods:

• * Utilized a novel system for live-cell observation of meiotic chromosome congression and segregation in maize.
• * Employed combined in situ hybridization and immunocytochemistry.
• * Analyzed chromosome movement rates and microtubule-kinetochore/neocentromere interactions.

Main Results:

• * Neocentromeres are active from prometaphase through anaphase, moving poleward at rates up to 1.4 micron/min, exceeding normal chromosome movement (0.79 micron/min).
• * Kinetochore-mediated chromosome movement is only marginally affected by linked neocentromere activity.
• * Neocentromeres associate laterally with microtubules, unlike kinetochores, and their movement correlates with knob size, suggesting microtubule depolymerization is not required.

Conclusions:

• * Neocentromeres are mobilized on microtubules via minus end-directed motor proteins interacting with knob DNA.
• * Neocentromere activity does not significantly impede normal kinetochore function.
• * Provides insights into the distinct mechanisms of chromosome movement during meiosis.