Analyzing the complex machinery of cell wall biosynthesis

The plant cell wall polymers make up most of the plant biomass and provide the raw material for many economically important products including food, feed, bio-materials, chemicals, textiles, and biofuel. This broad range of functions and applications make the biosynthesis of these polysaccharides a highly interesting target of scientific research. In this thesis a protein-protein interaction strategy was used to gain insight in the cell wall biosynthesis of Arabidopsis thaliana and to identify additional genes involved in this process. Using the membrane based yeast two hybrid system several distinct goals have been reached in this thesis, i) the characterization of the rosette structure by resolving the organization of the different cellulose synthase proteins in the complex, ii) the identification of unknown components of the cellulose synthezing machinery, iii) the confirmation of a xyloglucan synthesizing complex and the identification of several of its components. On the whole, this work has generated an effective tool in cell wall research and identified new players in the biosynthesis of both cellulose and xyloglucan. <br/

KORRIGAN1 Interacts Specifically with Integral Components of the Cellulose Synthase Machinery

Cellulose is synthesized by the so called rosette protein complex and the catalytic subunits of this complex are the cellulose synthases (CESAs). It is thought that the rosette complexes in the primary and secondary cell walls each contains at least three different non-redundant cellulose synthases. In addition to the CESA proteins, cellulose biosynthesis almost certainly requires the action of other proteins, although few have been identified and little is known about the biochemical role of those that have been identified. One of these proteins is KORRIGAN (KOR1). Mutant analysis of this protein in Arabidopsis thaliana showed altered cellulose content in both the primary and secondary cell wall. KOR1 is thought to be required for cellulose synthesis acting as a cellulase at the plasma membrane–cell wall interface. KOR1 has recently been shown to interact with the primary cellulose synthase rosette complex however direct interaction with that of the secondary cell wall has never been demonstrated. Using various methods, both in vitro and in planta, it was shown that KOR1 interacts specifically with only two of the secondary CESA proteins. The KOR1 protein domain(s) involved in the interaction with the CESA proteins were also identified by analyzing the interaction of truncated forms of KOR1 with CESA proteins. The KOR1 transmembrane domain has shown to be required for the interaction between KOR1 and the different CESAs, as well as for higher oligomer formation of KOR1

Interactions between membrane-bound cellulose synthases involved in the synthesis of the secondary cell wall

It has not yet been reported how the secondary CESA (cellulose synthase) proteins are organized in the rosette structure. A membrane-based yeast two-hybrid (MbYTH) approach was used to analyze the interactions between the CESA proteins involved in secondary cell wall synthesis of Arabidopsis and the findings were confirmed in planta by bimolecular fluorescence complementation (BiFC) assay. Results indicated that although all CESA proteins can interact with each other, only CESA4 is able to form homodimers. A model is proposed for the secondary rosette structure. The RING-motif proved not to be essential for the interaction between the CESA protein

Limited impact of deforestation- and conversion-free soy supply chains from South America on European producer and consumer prices

The EU is developing a law to ban the placing on the market of products associated with deforestation and forest degradation. This report estimates the impact of this law on soy supply chains, on EU producers feeding their animals partly with soy (meal), and on consumer products where soy is embedded. More concretely, this study estimates the extra cost of deforestation-and conversion-free(DCF)soy supply from Argentina and Brazil to the EU and the impact on the price of production and consumption in the EU, for e.g. pig meat, chicken meat, milk, beef, salmon and eggs. The study points out that for Argentina, in the highest-cost scenario, for a single trader who sets up a segregated DCF supply to the EU, these extra costs are about 1% of the cost of producing and exporting soy to the EU. In a more probable scenario, where Argentinian traders collaborate to setup a 100% DCF supply,the costs per tonne are three times lower. For Brazil the costs are estimated to be 10-20timeslowerthan for Argentina. This is due to the larger volumes exported from Brazil and reflects actions already taken in Brazil, including to comply with the Amazon Soy Moratorium. These costs will have very limited impact in the EU.With the highest-cost scenario for Argentina, the extra cost represents up to 0.2% of the average turnover of specialized farms in The Netherlands producing pigs, chicken meat, eggs or dairy. We estimate a slight decrease in the income of these producers of animal products in a transition period, varying between 0.3% for dairy farmers and 3% for pig farms, laying hen farms and poultry farms.In the “most probable scenario” the income for the farmers is estimated to decrease by up to 0.6% in a transition period.When the EU regulation is implemented, however, all European producers will switch to DCF soy for animal feed, and this cost increase will be passed on to the subsequent links in the supply chain through the functioning of the market. After the transition period, which may take a few years, there will no longer be a negative effect on producers' income. EU consumers will not notice an increase in the price of these products(all other things being equal). This is because under the highest-cost scenario the extra cost for DCF soy is only about 1% of the total cost to produce and transport soy to the EU, and because the cost of soy is only a fraction of the overall cost of consumer products. More concretely, the average price of a kilogram of pork meat in Belgian supermarkets is currently €8.18;when the EU law comes into place, the price will still be €8.18, all other things being equal