Protein-Protein Interactions Linking Signaling and Cytoskeletal Proteins Involved in Wood Formation

Efforts to identify and characterize genes that regulate wood formation have been greatly aided by the emergence of poplar (Populus trichocarpa) as a genomic model for tree research.  Specifically, the availability of a sequenced genome facilitates in depth transcriptomic and proteomic analyses that were not possible just a few years ago.  These new capabilities coupled with facile transgenesis make poplar an excellent model for investigating the functional genomics of wood formation as a major component of tree biomass accumulation.  We have cloned a portion of the poplar woody biomass ORFeome comprising approximately 350 genes strongly upregulated in poplar wood-forming tissue (xylem).  We are in the process of screening by yeast two-hybrid (Y2H) over 200 of these proteins as bait against a xylem cDNA prey library. Here we focus on results obtained for selected signaling proteins that interact with coiled-coil proteins that are known or predicted cytoskeletal proteins.  For example, a poplar ROP GTPase was found to interact with five distinct coiled-coil proteins, and a calcineurin B-like interacting protein kinase (CIPK) also interacted with a putative cytoskeletal protein with coiled-coil domains.  We are currently testing other coiled-coil, predicted cytoskeletal proteins that are members of the biomass ORFeome for their ability to interact with each other and with both the ROP GTPase and CIPK proteins in a Y2H binary matrix.  Additionally, we are screening biomass ORFeome members predicted to encode intrinsically disordered proteins, as these are significantly more likely to be hub proteins that interact with numerous partners.