Comparative studies of the secretome of fungus-growing ants

Leafcutter ants of the species Acromyrmex echinatior live in symbiosis with the fungus Leucoagaricus gongylophorus. The ants harvest fragments of leaves and carry them to the nest where they place the material on the fungal colony. The fungus secretes a wide array of proteins to degrade the leaves into nutrients that the ants can feed on. The focus of this study is to discover, characterize and compare the secreted proteins. In order to do so cDNA libraries are constructed from mRNA extracted from the fungus material. The most efficient technology to screen cDNA libraries selectively for secreted and membrane-bound proteins is the TAST (Transposon Assisted Signal Trapping) technology (Becker et al. 2004,Microbiol Methods 57, 123-133). The TAST screening will give a list of full length gene sequences encoding secreted proteins. The main part of the secretome will consist of biomass degrading enzymes, but also antimicrobial proteins will probably be in the secretome. To date only a few enzymes from the Leucoagaricus secretome have been identified. We expect to discover novel proteins and to gain a better understanding of the biodegrading pathways of Leucoagaricus. Ultimately, this work may identify enzymes that can be used in biomass conversion processes. (Poster # 426)