Aspergillus nidulans: a bioresource for green biotechnology

Cellulose is the most abundant biopolymer on earth and is of great economic importance. It is the main constituent of cotton and wood, which represent the major resources for all cellulose products. Together with lignins, structural proteins and noncellulosic polysaccharides, (e.g. pectins, xyloglucans, xylans), cellulose forms a complex network reinforced by multiple cross-links. This network accommodates a variety of mechanical requirements during plant life and its physical and mechanical properties are comparable to those of the best synthetic materials. These properties are exploited in various products such as paper, textiles and building materials. In addition to these traditional sectors, there is a great potential to develop carbohydrate-based materials that combine environmental friendliness and biocompatibility with high performance and increased functionality, through the metabolic engineering of plants. The possibility of marrying the properties of naturally-occurring biopolymers results in new blends with improved features, which can eventually be exploited for biotechnological applications. An emblematic example is the introduction of the fungal chitin biosynthetic pathway in plants: chitin does not occur naturally in plants, but the introduction of chitin or its partially deacetylated form (chitosan) would confer interesting properties, which can be exploited in different industrial sectors. For instance, the synthesis of chitin would increase the tensile strength of the plant, which constitutes an important step towards materials development. This feature is also of particular importance in crops subject to brittle snap. In addition to this, it is known that treatment of plant tissues with chitin or chitosan elicits antifungal and antiviral defense responses that protect the plant from the further spread of pathogens. It would therefore be possible to create plants with an enhanced resistance to pathogens attack, by introducing key enzymes involved in chitin biosynthesis. In a longer perspective, this technology can be transferred to trees and thus constitute a precious toolbox for the forest industry, which is an important export engine for Austria. In the light of the wide range of applications of cellulose, it is proposed here to exploit the cell wall biosynthetic genes of the model filamentous fungus Aspergillus nidulans as a bioresource for the metabolic engineering of plants. For this purpose, it is proposed: - To unveil the role of some poorly or non- characterized glycosyltransferases (GTs) responsible for cell wall formation in A. nidulans, using an overexpression and a reverse genetics approach (e.g. gene knockdowns and knockouts). - To introduce the chitin synthase (Chs) and oxaloacetate acetylhydrolase (Oah) genes from A. nidulans in the model organism Arabidopsis thaliana to create plants with modified cell wall composition and potentially altered chemo-physical surface properties, that may increase resistance to biotic stresses and potentially represent new biomaterials. In summary, by learning from nature, this project will lay the basis for the development of biomimetic materials combining environmental friendliness and biocompatibility with enhanced performance and functionality. In a longer perspective, this knowledge will facilitate the development of significant applications based on plant biomass. The proposed project shows the potential of redirecting plant metabolism towards the biosynthesis of novel polysaccharides, which could result in improved properties of cellulose fibers.