Investigating the functions and interactions of FLAs in secondary cell walls

Ma Y1,2, Zeng W3, Bacic A1,2 and Johnson KL1,2

  1. University of Melbourne.
  2. La Trobe University.
  3. Zhejiang Agriculture and Forestry University.

Our natural and plantation forests represents 90% of the captured carbon and is our most renewable bio-resource. The bulk of the biomass consists of secondary cell walls, which are thick, rigid and deposited on the inner side of the primary walls in specialized tissues. Secondary cell wall development is an area of intense interest given its importance for plant growth, water conductance and human applications such as biofuels, bio-inspired materials/bio-composites, construction and paper. A group of plant cell wall glycoproteins, the Fasciclin-Like Arabinogalactan proteins (FLAs) have been implicated in regulating secondary cell wall development and influencing their biomechanical properties. FLAs are a sub-class of the arabinogalactan-proteins (AGPs), glycoproteins implicated in cell wall sensing and signalling and proposed to cross-link to pectins in the wall. The fasciclin (FAS) domain has been shown to be involved in protein-protein interactions and development in mammals, insects and algae. Glycoproteins such as FLAs are therefore fascinating ’chimeric’ molecules with a number of interesting properties; being able to potentially form protein-protein, protein-carbohydrate and carbohydrate-carbohydrate interactions in the wall. Using Arabidopsis as a model system, we have focused on a subset of FLAs (FLA11, FLA12 and FLA16) that are expressed in cells undergoing secondary cell wall development. Preliminary evidence suggests these FLAs influence the amount and angle of cellulose deposition, the most abundant cell wall polymer that forms the structural basis for all cell walls. Through mutant studies, biomechanical analysis, examination of FLA location and bioinformatics we are gaining insight into the function(s) of these complex glycoproteins.