Research review paper Genetic engineering of filamentous fungi — Progress, obstacles and future trends Vera Meyer ⁎ TU Berlin, Institut für Biotechnologie, Fachgebiet Mikrobiologie und Genetik, Gustav-Meyer-Allee 25, D-13355 Berlin, Germany Received 28 August 2007; received in revised form 3 December 2007; accepted 4 December 2007 Available online 14 December 2007 Abstract Filamentous fungi are widely used in biotechnology as cell factories for the production of chemicals, pharmaceuticals and enzymes. In order to improve their productivities, genetic engineering strategies can be powerful approaches. Different transformation techniques as well as DNA- and RNA-based methods to rationally design metabolic fluxes have been developed for industrially important filamentous fungi. However, the lack of efficient genetic engineering approaches still forms an obstacle for a multitude of fungi producing new and commercially interesting metabolites. This review summarises the variety of options that have recently become available to introduce and control gene expression in filamentous fungi and discusses their advantages and disadvantages. Furthermore, important considerations that have to be taken into account to design the best engineering strategy will be discussed. © 2007 Elsevier Inc. All rights reserved. Keywords: Filamentous fungi; Genetic and metabolic engineering; Transformation; Gene targeting; ku70; Antisense; RNAi; Hammerhead ribozyme Contents 1. Introduction ............................................................. 177 2. Approaches to genetic transformation ................................................ 178 3. Re-engineering gene targeting .................................................... 179 4. RNA technologies for genetic engineering .............................................. 180 5. Designing an engineering strategy .................................................. 182 6. Conclusions and prospects ...................................................... 183 References ................................................................. 183 1. Introduction The ability of filamentous fungi to grow on rather simple and inexpensive substrates as well as their capacity to produce a wide range of commercially interesting metabolites have attracted considerable interest to exploit them as production organisms in biotechnology. Nowadays, filamentous fungi are used in biotechnology as cell factories for a wide range of products. Diverse compounds ranging from simple organic acids to complex secondary metabolites are produced for the use in various market segments (Table 1). Due to their exceptional high capacity to express and secrete proteins, filamentous fungi have become indispensable for the production of enzymes of fungal and non-fungal origin. Cur- rently, native or recombinant enzymes are mainly produced by Aspergillus niger, A. oryzae and Trichoderma reesei and also other strains are currently under development (Punt et al., 2002). In addition, filamentous fungi naturally produce an astonishing wealth of secondary metabolites and a few of them are Available online at www.sciencedirect.com Biotechnology Advances 26 (2008) 177 – 185 www.elsevier.com/locate/biotechadv ⁎ Tel.: +49 30 314 72827; fax: +49 30 314 72922. E-mail address: v.meyer@lb.tu-berlin.de. 0734-9750/$ - see front matter © 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.biotechadv.2007.12.001