Comparative EST analysis of a Zoophthora radicans isolate derived from Pieris brassicae and an isogenic strain adapted to Plutella xylostella.

Zoophthora radicans is an entomopathogenic fungus with the potential to be used as an insect biological control agent. To better understand the mechanisms used by Z. radicans to infect different hosts, we generated expressed sequence tag (EST) datasets from a Z. radicans strain originally isolated from Pieris brassicae, and an isogenic strain passaged through Plutella xylostella. In total, 1839 ESTs were generated which clustered into 466 contigs and 433 singletons to provide a set of 899 unique sequences. Approximately 85 % of the ESTs were significantly similar (E< or =e(-03)) to other fungal genes, of which 69.6 % encoded proteins with a reported function. Proteins involved in protein synthesis and metabolism were encoded by 38.3 % of the ESTs, while 26.3 % encoded proteins involved in cell-cycle regulation, DNA synthesis, protein fate, transport, cell defence, transcription and RNA synthesis, and 4.9 % encoded proteins associated with cellular transport, signal transduction, control of cellular organization and cell-wall degradation. Several proteinases, including aspartic proteinases, trypsins, trypsin-like serine proteases and metalloproteases, with the potential to degrade insect cuticle were expressed by the two isolates.