Research in the group Cellular Coordination focuses on understanding processes and underlying principles that regulate plant growth and development. In plants, growth is restricted by the cell wall that surrounds cells outside the plasma membrane and physically glues neighboring cells. Deposition of cell wall material is mediated by the plant cytoskeleton, comprised of actin filaments and microtubules. In interphase cells, cortical microtubules serve as tracks for plasma membrane-localized cellulose synthase complexes. The orientation of cortical microtubules thus determines the direction of cellulose deposition and consequently of cell expansion. Plant-specific microtubule arrays additionally contribute to establishment of division planes and formation of new cell plates during cell division. Networks of microtubule-associated proteins act in concert to coordinate microtubule organization, dynamics and, e.g., plasma membrane tethering of microtubules, and serve to integrate incoming signals from developmental and environmental stimuli into reorganization of the microtubule cytoskeleton.
Signaling via the second messenger calcium plays a prominent role in plants for coordinating numerous developmental processes and responses to environmental cues. Generation of stimulus-specific calcium signatures, decoding of the encrypted information, and mounting specific cellular responses are integral phases of the transduction process, with differential interactions between calcium sensor proteins, such as calmodulin (CaM) and closely related CaM-like proteins (CML), and their molecular targets at its nexus. We previously identified a novel class of CaM/CML target proteins in Arabidopsis, the 33-member IQD (IQ67-DOMAIN) family of largely unknown functions. The plant-specific IQD family represents one of the largest classes of putative CaM/CML targets. Molecular, biochemical and histochemical analysis of the entire Arabidopsis IQD family indicate that IQDs provide an assortment of scaffold proteins at microtubules, the plasma membrane and in the nucleus that regulate plant growth and development. Very little is known in plants about molecular mechanisms of IQD protein function and the underlying biological roles. Our studies of the IQD family thus provide a unique opportunity to address how early signaling is integrated at the cell wall-plasma membrane-cytoskeleton continuum during growth regulation.