Insight into Filamentous Fungal Secretion and Evolution through Genomic Analysis

Abstract

Filamentous fungi are of broad economic importance due to their roles in industry, medicine and agriculture. There are several filamentous fungi, such as Trichoderma reesei, which have been harnessed as protein factories due to their immense secretion capacity. Unfortunately, their full potential cannot be exploited due to an incomplete understanding of the pathways and genes involved in the fungal secretion system. Through the development of bioinformatic tools and the use of genomic technologies including expressed sequence tags and bacterial artificial chromosomes, the genome of T. reesei has been partially characterized and a number of genes involved in the secretion system have been identified.

Pathogenic fungi, such as Magnaporthe grisea, are of great economic importance due to their devastating effect on agriculture. M. grisea is responsible for the loss of incredible amounts of rice crop yearly and has recently had its genome completely sequenced and annotated. The genome sequence has revealed the set of transposable elements in M. grisea which have then been analyzed using gene genealogies and the coalescent. The genealogies and coalescent have revealed that all elements analyzed showed a rapid expansion at some point in the past. This can be explained as a genomic event leading to the acceptance of transposable element activity most likely caused by the loss of genomic defense mechanisms. As a pathogen, the ability to evolve quickly in the face of plant defense mechanisms is essential. Transposable element activity can provide means for rapid evolution and this acceptance may represent a shift of these elements from genomic parasitism to mutualism.