Sequence analysis of insecticidal genes from Xenorhabdus nematophila BP and insecticidal activity

XnBP83 is a clone which had oral toxicity to Helicoverpa. armegera screened from the cosmid library of Xenorhabdus. nematophilus BP. Comsmid XnBP83 was sequenced using a strategy of subcloning and primer-walking DNA sequencing. The inserted sequences of XnBP83 have 38 939 bp including 5 ORFs that are associated to the insecticidal activity: xptA1, xptB1 xptC1, xptA2 and xptD1. The results of sequence analysis showed that: 1) The xptD1 of XnBP83 is incomplete, and shares 99% predicted amino acid sequence identity to that of X. nematophilus PMF1296. 2) The xptA1 of XnBP83 has 7 569 bp nucleotides, encoding 2 520 amino acids which shares 98% identical amino acid residues with that of PMF1296. 3) The xptB1 has 3 051 bp nucleotides, encoding 1 016 amino acids. The XptB1 sequence shares 98% identical amino acid residues with XptB1 of PMF1296. There are 28 different amino acids from 620 to 650 amino acids. 4) The xptC1 of X. nematophilus BP has 4 225 bp, encoding 1 408 amino acids. The XptC1 sequence shares 96% identical amino acid residues with that of X. nematophilus PMF1296. There are 18 different amino acids from 627 to 646 amino acids. The amino acid sequence with TAQRYLAK was inserted to downstream to 232nd amino acid. And 5) The xptA 2 has a length of 7 574 bp, encoding 2 524 amino acids. The XptA2 sequence shares 90% identical amino acid residues with that of PMF1296. Two distinctly divergence amino acid regions present from 788 to 855 and from 1 630 to 1 784 amino acids. Oral bioassay of the supernatant and cell sediment of XnBP83 against H. armegera. S. exigua, S. litura and T. ni showed that XnBP83 had broad-spectrum insecticidal activity.