The microtubule cytoskeleton is essential for numerous critical processes in eukaryotes. The versatility of the microtubule cytoskeleton derives from its ability to form distinct arrays depending on cellular needs. We use the Arabidopsis thaliana cortical microtubules as an experimentally tractable model system to elucidate the molecular mechanisms for the dynamics, spatial organization and function of the microtubule cytoskeleton. Current areas of research in the lab are:
Mechanisms controlling microtubule dynamics and organization
Cells control the inherent dynamics of microtubules through a host of microtubule-associated proteins, some of which target microtubule tips while others bind to the microtubule lattice to either stabilize, destabilize or crosslink microtubules. Together, these regulatory proteins provide a molecular toolkit by which cells construct and dynamically remodel microtubule arrays.
Current research questions:
1. Mechanisms that regulate katanin activity: how do cells tune the activity of the microtubule severing enzyme katanin to achieve different cellular, developmental and physiological functions?
2. Role of microtubule bundling: how do different microtubule crosslinking proteins affect microtubule organization and their capacity to reorganize?
3. Functions of microtubule tip regulators: what is the biochemical and structural basis by which new plant microtubule plus-end and minus-end regulators target and modulate microtubule tip behavior?
How cortical microtubules orchestrate cell wall deposition
Cortical microtubules guide the movement of cellulose synthase complexes that extrude cellulose into the cell wall and are thought to serve as tracks for molecular motor proteins that transport vesicles containing noncellulosic cell wall components. Our work focuses on the Arabidopsis FRA1 kinesin to investigate how membrane trafficking and cortical microtubules interact during cell wall biogenesis. Our previous work showed that FRA1 moves processively along cortical microtubules and is important for high-capacity secretion of matrix polysaccharides such as pectin. We uncovered an importin-beta as a key regulator of FRA1’s motility and turnover and found that FRA1 stabilizes the sites of cell wall deposition by affecting the microtubule localization of CMU proteins that rivet cortical microtubules in place.
Current research questions:
1. Identify cargo of the FRA1 kinesin: how does FRA1 contribute to membrane trafficking and does it transport vesicles containing matrix polysaccharides?
2. Investigate the role of FRA1 in secondary cell wall formation: how does FRA1 contribute to the secretion of secondary cell wall material?
3. Regulators of FRA1: what are the mechanisms that activate FRA1 motility? Do CMU proteins compete with cargo for binding to the FRA1 tail domain?
Role of mechanical stimuli in plant cell morphogenesis
Both plant and animal cells sense and respond to mechanical cues from their environment. A critical, but often overlooked, component of this process is that cells themselves alter these cues by modifying their extracellular microenvironment and through connections with adjacent cells. This process is further complicated by mechanical stresses created due to differential growth rates and growth directions of cells within plant tissues. Unraveling these complex and recursive effects requires new tools and methodologies to probe the constant interplay between mechanical and biochemical stimuli that together shape plant morphogenesis.
Current research questions:
1. Engineer a plant-on-a-chip microdevice: develop methods to grow plant cells on artificial matrices to study how they sense and respond to defined mechanical forces under controlled conditions.
2. Mechanisms underlying chiral plant growth patterns: how do certain mutations that affect cortical microtubules generate chiral growth of plant tissues and organs?