Dr. Beers is engaged in the discovery and characterization of genes that influence the differentiation and function of secondary xylem (wood) and phloem.
Humans use wood as raw material for a wide variety of essential and non-essential products, and our dependence on wood is poised to increase significantly as efforts to improve the efficiency of cellulosic biofuel production intensify. Yet, despite the long history of wood use, plant scientists only recently began to provide in-depth characterizations of genes that regulate wood formation. Contributing to this effort has been the main focus Dr. Beers’ work at Virginia Tech. During that time he and his laboratory group members pioneered the use of Arabidopsis as a model for the molecular biology of wood formation (Zhao et al., 2000) and published the first genome-wide transcript profile for xylem and phloem from any plant (Zhao et al., 2005).
His transcript profiling experiments were the foundation for subsequent reverse genetic experiments that revealed the functions of the xylem-associated proteases XCP1 and XCP2 (Avci et al., 2008), which have become widely used markers for xylem differentiation in Arabidopsis and other models. Although it is often stated that proteases such as XCP1 and XCP2 play roles in xylem cell autolysis, little direct evidence exists to support such claims. In Avci et al. (2008), in collaboration with the Haigler lab at NCSU, the Beers lab showed that normal progression of autolysis in xylem tracheary elements was aided by XCP1 and XCP2, thus providing the first detailed characterization of trafficking and activity of a proteolytic enzyme during tracheary element differentiation. They also discovered and characterized XND1, the first NAC domain transcription factor gene shown to be capable of blocking tracheary element formation (Zhao et al., 2008; Grant et al., 2010).
Beers is also interested in phloem cell differentiation and phloem-mediated signaling. He characterized two phloem-specific Myb-related genes, MYR1 and MYR2, which negatively regulate a shade avoidance-like response in Arabidopsis. UnlikephyB mutants, however, which constitutively exhibit the shade avoidance syndrome, the myr1 myr2 phenotype is evident only under low light intensity (Zhao et al., 2011). Further characterization of MYR1 and MYR2 can lead to a more detailed understanding of how the phloem contributes to the integration of the quality and quantity components of light and transduces those signals. Additionally, more work is needed to define the role played by the phloem as a regulator of carbon partitioning and wood formation in trees.
Gains in knowledge of the molecular genetics of wood formation have relied mainly on cloning of genes responsible for vascular mutants or characterization of selected genes that are transcriptionally co-regulated with wood cell differentiation. However, provided they share the same compartment in a cambium or xylem cell at some point in time, two interacting proteins need not be transcriptionally co-regulated to be important components of a wood formation network. Thus, protein-protein interaction (PPI) networks are important complements to transcriptome networks as tools for gene discovery. The Beers lab is currently working on a PPI project based on genes expressed in poplar wood-forming tissue. Ultimately, when enough experimentally determined PPIs are available, development of dense PPI networks integrated with transcriptome, metabolome, and protein-DNA interaction (PDI) networks will fuel a surge of new research activity in functional systems biology.