Preprophase band

Preprophase band (PPB) is a microtubule array found in plant cells that are about to undergo mitosis. It is a ring of microtubules and associated proteins that forms just beneath the plasma membrane, encircling the cell at the future site of the cell plate formation. The preprophase band predicts the future axis of cell division, playing a crucial role in determining the spatial organization of the newly-formed cells, which is essential for the development and morphology of a plant.

Formation and Function

The formation of the preprophase band marks the onset of preprophase, a unique phase in the cell cycle of plant cells that precedes prophase of mitosis. The PPB assembles during the late G2 phase of the cell cycle and disassembles before the breakdown of the nuclear envelope, marking the transition to prophase. The exact mechanism of PPB formation is not fully understood, but it involves the reorganization of microtubules around the cell nucleus, guided by the action of microtubule-associated proteins (MAPs).

The primary function of the preprophase band is to delineate the future division plane of a cell. It does so by establishing a spatial memory that guides the assembly of the phragmoplast and the formation of the cell plate during cytokinesis. This ensures that cell division is precisely oriented in relation to the plant's overall architecture, which is critical for the formation of organized tissues and for the plant's developmental processes.

Components

The preprophase band is composed of several key components:

• Microtubules: The main structural component of the PPB, providing the framework for the band's formation.
• Microtubule-associated proteins (MAPs): Proteins that stabilize microtubules and regulate their dynamics during PPB assembly and disassembly.
• Motor proteins: Including kinesins and dyneins, which are involved in the movement of microtubules and other components during PPB formation.

Significance in Plant Development

The orientation of cell division controlled by the preprophase band is of paramount importance in plant development. It influences the pattern of cell division in developing tissues, affecting the shape and function of organs. Mutations affecting PPB components can lead to disorganized growth and developmental abnormalities, highlighting the critical role of the PPB in plant biology.

Research and Applications

Research on the preprophase band has provided insights into the molecular mechanisms of cell division orientation and spatial organization in plants. Understanding the PPB's role in cell division has implications for improving plant breeding and biotechnology, allowing for the manipulation of plant architecture for enhanced yield and resilience.