Crema of the Crop: Producing Designer Heteromannans in Yeast and Plant Cell Walls

• Applicant: Professor Dr. Catalin Voiniciuc
• Subject Area: Plant Biochemistry and Biophysics ; Plant Genetics and Genomics ; Plant Cell and Developmental Biology
• Term: from 2018 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 414353267

Sugars are fundamental to all living cells. Plant cells are shaped and strengthened by carbohydrate-rich walls, and can thus survive in a wide range of environments. Since cell wall polysaccharides make up the bulk of the plant biomass, they represent the most abundant source of renewable material on Earth. Nevertheless, polysaccharides elongation and substitution remain poorly understood processes. Plant cell walls primarily consist of cellulose microfibrils cross-linked by hemicellulose and, to a lesser extent, pectin. Junctions between these distinct classes of polysaccharides govern the biomechanical properties of the wall. Heteromannan (HM) is regarded as the most ancient hemicellulose, and is found throughout the plant kingdom. Despite their widespread distribution, the biosynthesis of HM polysaccharides has been grossly understudied relative to other plant cell wall components. The global demand for HM extracted from plant seeds has increased substantially in recent years due to its utility as an environmentally-friendly thickener in foods, cosmetics, and in many other industries. Furthermore, as the main component of the crema atop espresso, HM enhances the texture of the coffee beverage consumed by millions around the world on a daily basis.Although the genomics era has ushered the identification of multiple genes involved in HM biosynthesis, most of them remain to be functionally characterized. I will use synthetic biology tools to gain mechanistic insight into HM biosynthesis. Yeast cell walls lack hemicelluloses, but can be quickly engineered to accumulate large amounts of HM by expressing plant glycosyltransferases. I therefore propose to decipher the biosynthesis of plant HM with an unprecedented precision by combing yeast genetic engineering with state-of-the-art biochemical analyses of cell wall structure. I will thus characterize the key proteins required for HM production and explore how they function together by sequentially building HM backbones in yeast, then substituting them with specific side chains. I will then engineer plant seeds to accumulate tailor-made HM structures in order to validate the discoveries from yeast, and to explore how remodelled hemicelluloses impact the architecture and properties of the plant cell wall. I will thus address fundamental gaps in plant biology and synthesize designer HM polymers in both yeast and plant cell walls, whose structure and function could be tailored to produce valuable materials for specific industrial applications.

• DFG Programme: Research Grants