Cloning and expression analysis of a predicted toxin gene from Photorhabdus sp. HB78

Abstract

The genome of the insect pathogen Photorhabdus luminescens TT01 strain contains multiple genes predicted to encode toxins. One of these, plu0840, has 55% sequence identity with an enterotoxin from Aeromonas hydrophila. In order to further investigate this gene, we successfully cloned the complete plu0840 from Photorhabdus sp. HB78 and expressed it as a GST-Plu0840 fusion protein in Escherichia coli BL21(DE3) using pGEX-4T-l as a vector. Most of GST-Plu0840 was insoluble and sequestered into inclusion bodies. The inclusion bodies were harvested and dissolved. The resultant protein was cleaved and purified from the GST-tag. Oral bioassay showed that Plu0840 inhibited growth of Spodoptera litura and Spodoptera exigua larvae.