Research Report

Draft Genome Sequence of Bacillus thuringiensis Strain S2685-1, a Novel Strain with High Larvacidal Toxicity against Helicoverpa zea  

Zhou  Y.1,2,* , Wu  Z.Q.3,* , Liu  P.P.3 , Wei  Y.J.4 , Zhang  W.F.5 , Zhang  Y.4 , Liu  S.K.3 , Fang  J.X.J.1,2,3,6
1 Hainan Institute of Tropical Agricultural Resources (HITAR), Sanya, China
2 College of Life and Technology Science, Guangxi University, Nanning, Guangxi, China
3 Alkali Soil Natural Environmental Science Center(ASNESC), Northeast Forestry University, Harbin, 150040, China
4 College of Bioinformatics Science and Technology, Harbin Medical University, Harbin, China
5 College of Life Sciences, Hainan Normal University, Haikou, China
6 The HITAR Institute Canada Inc. British Columbia, Canada * These authors contributed equally.
Author    Correspondence author
Bt Research, 2015, Vol. 6, No. 9   doi: 10.5376/bt.2015.06.0009
Received: 30 Oct., 2015    Accepted: 20 Nov., 2015    Published: 16 Dec., 2015
© 2015 BioPublisher Publishing Platform
This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Preferred citation for this article:

Zhou Y., Wu Z.Q., Liu P.P., Wei Y.J., Zhang W.F., Zhang Y., Liu S.K., and Fang J.X.J., 2015, Draft genome sequence of Bacillus thuringiensis strain S2685-1, a novel strain with high larvacidal toxicity against Helicoverpa zea, Bt Research, Vol.6, No.9 1-4 (doi: 10.5376/bt.2015.06.0009)


Here, we report the draft genome sequence of Bt Strain S2685-1. It consists of 262 scaffolds with a GC content of 34.89% and a total length of 5,685,503 bp. The assemble analysis shows that there are four replicons in S2685-1, including a circular chromosome of 5,287,484 bp with 6326 ORFs and 5429 CDSs and three circular plasmids, which are named S2685-1P01 (151,717 bp), S2685-1P02 (196,775 bp) and S2685-1P03 (49,527 bp), respectively. The average GC content of the chromosome sequence is 35.08%, while that of the plasmid sequences are 31.86%, 32.23% and 34.89%, respectively. Two crystal genes have been predicted from this strain but they share 100% sequence identity to cry1Ac in HD73. It also had been identified with high larvacidal toxicity against Helicoverpa zea in S2685-1.

Bacillus thuringiensis; S2685-1; Larvacidal Toxicity; Helicoverpa zea

Results and Discussion
Bacillus thuringiensis is a gram-positive entomopath- ogenic bacteria (Broza et al., 1986), used as microbial insecticide widely and successfully in agriculture. It can produce lots of insecticidal parasporal crystal proteins during sporulation (Crickmore et al., 1998). The present studies showed that insecticidal crystal proteins (ICPs) exhibited specific insecticidal activity against insects belonging to the orders Lepidoptera, Diptera, Coleoptera, Hymenoptera, Homoptera, Orthoptera, Mallophaga, nematodes, mites and protozoa (Schnepf et al., 1998), even were toxic to cancer cell (Mizuki et al., 1999). B. thuringiensisstrain S2685-1 isolated from Heilongjiang Liangshui National Nature Reserve belongs to the Hainan Institute of Tropical Agricultural Resources (HITAR). The scanning electron microscope observation showed that it was able to generate bipyramidal parasporal crystals and it was highly toxic to corn earworm (Helicoverpa zea) (Fang et al., 2015). Here, we present the draft genome sequence of B. thuringiensis strain S2685-1 and provide many valuable information of the sequence, which will help for further understanding the pathogenicity of B. thuringiensis against Helicoverpa zea.

The sequencing of Bt S2685-1genome was performed in the Shanghai Human Genome Center (CHGC, Shanghai, China) by using an Illumina HISeq2000 Sequencing platform. The draft genome sequence consists of 262 scaffolds with a GC content of 34.89% and a total length of 5,685,503 bp. Gene predictions and annotations were completed using the Glimmer software (Delcher et al., 2007) and MetaGeneMark software (Zhu et al., 2010). Both tRNA and rRNA genes were identified by tRNAscan (Lowe and Eddy, 1997) and rRNAmmer (Lagesen et al., 2007), respectively. Identification of the insecticidal parasporal crystals protein gene was accomplished by the local database comparison and DELTA-BLAST.

The draft genome of B. thuringiensis strain S2685-1 contains four replicons: a circular chromosome of 5,287,484 bp and three circular plasmids, which were named S2685-1P01 (151,717 bp), S2685-1P02 (196,775 bp) and S2685-1P03 (49,527 bp), respectively (Figure 1).
 Figure 1 Draft genome sequence map of S2685-1
The chromosome encodes 6326 predicted open reading frames (ORFs) including 5429 coding sequences (CDSs) and the total length of genes was 4,462,815 bp, which makes up 84.4% of genome. The G+C content of chromosome was 35.08% and 53 tRNA and 5 rRNA operons were predicted. Approximately, 2233 CDSs were annotated into the 189 pathwaysby using KAAS (Moriya et al., 2007). These plasmids contain a total of 533 predicted ORFs. The G+C contents range from 31.86% to 34.89% (Table 1).
Table 1 Genome features of Bacillus thuringiensis S2685-1
Two crystal genes have been predicted from this strain, and they located on plasmid S2685-1P01 and S2685-1P02, respectively. Strangely, this two crystal genes share 100% sequence identity to cry1Ac, which has been identified in B. thuringiensis serovar kurstaki str. HD73. Based on the phylogenetic trees from the chromosome, strain B. thuringiensis S2685-1 was found to be closest to B. thuringiensis serovar kurstaki str. HD73 (Song et al., 2013).

In brief, the genome sequence of S2685-1 strain not only enriches the genome database of B. thuringiensis, but also facilitates understanding the function of toxic proteins against Helicoverpa zea.

Nucleotide sequence accession
The draft genome sequence of Strain S2685-1 has not been yet included in the GenBank but deposited in the database maintained by the HITAR Institute Canada Inc. The annotated chromosome and plasmids would be available upon request.

This Project of Bt Genome Sequence was initiated and funded by the HITAR Institute Canada Inc. in British Columbia, Canada and Guangxi Graduate Education Innovation Projects (YCBZ2014006).

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