Regulation of cellulose biosynthesis and deconstruction by protein phosphorylation
Shaolin Chen^1*, Zhiqi Hao², Chris Somerville¹

1 Energy Biosciences Institute, University of California, Berkeley, CA 94720, USA
2 Thermo Fisher Scientific Inc, 355 River Oaks Parkway, San Jose, CA 95134, USA
* Corresponding Author：Email: schen1@berkeley.edu

Abstract
The great abundance of cellulose places it at the forefront as a primary source of biomass for a renewable energy source, and a variety of efforts are underway to improve cellulose deconstruction for the production of cellulosic biofuels. However, the knowledge of how plant cells make cellulose and how microorganisms degrade cellulose remains very rudimentary. Understanding these processes will help optimize the production of cellulosic biofuels. Protein phosphorylation plays critical roles in regulating cellulose biosynthesis and deconstruction. Cellulose microfibrils are synthesized at the plasma membrane by cellulose synthase (CesA) complexes. The CesA1 and CesA3 components of cellulose synthase complexes are phosphorylated at sites clustered in two hypervariable regions of the proteins. Mutations of the phosphorylated residues to Ala (A) or Glu (E) alter anisotropic cell expansion and bidirectional motility of CesA complexes in the plasma membrane in rapidly expanding hypocotyls. In addition, protein phosphorylation regulates cell wall deconstruction by filamentous fungi. Here we present a mass spectrometry-based quantitative phosphoproteomics approach to identify the regulatory pathways that control the expression and secretion of cell wall degrading enzymes from the filamentous fungus Neurospora crassa.

Keywords: cell wall, biosynthesis, deconstruction, phosphorylation, CesA proteins, kinase