Han Lanlan

Cloning, Expression and Activity of cry1Ia Gene from Bacillus thuringiensis Isolate

A Full-length cry1Ia gene fragment, which obtained by PCR amplification with a pair of primers designed according to cryIa-type gene sequences and DNA from Bacillus thuringiensis Btc008 as template, was introduced into expression vector pET-21b and transformed into Escherichia coli BL21(DE3). Molecular weight of the induced express product was 81 kD. The encoded protein was composed of 719 amino acid residues and the predicted MW was 81.2 kD. The amino acid sequence of the Cry1Ia was very different from those of 12 known Cry1Ia-type proteins. This gene with accession number AF373207 was designated as cry1Ia8 by International Bt Insecticidal Gene Nomenclature Committee. The bioassay results indicated that the Cry1Ia toxin protein showed distinctly insecticidal activity against Ostrinia furnacalis and Plutella xylostella with LC50 of 0.268 μg/g and 2.227 μg/mL, respectively, while it also had insecticidal activity against Leguminivora glycinivorella,but no activity against Pyrrhalta aenescens. The novel cry1Ia8 gene will be new resource for the construction of genetically engineered bacterium and transgenic plant for biocontrol of insect pests. It is also available for screening gene stacks to delay the resistance produce of the pests.

Genetic Differentiation Analyses Based on mtDNA CO II Gene Sequences Among Different Geographic Populations of Aphis glycines (Hemiptera: Aphididae) in Northeast China

Abstract Aphis glycines (Hemiptera: Aphididae) is considered as a cosmopolitan pest of cultivated soybean, major difficulties in its control measures may be due to its higher genetic diversity; however, the knowledge about population genetic diversity of this species is limited. This study aimed to represent the genetic differentiation among different geographic populations of soybean aphid in Northeast China. In order to investigate and assess the genetic diversity, genetic differentiation, molecular variance, population structure, ecological importance and evolutionary history of A. glycines, we sequenced a fragment of one protein-coding gene, the cytochrome c oxidase II of mitochondrial DNA gene. The results showed that four haplotypes were defined among CO II gene of 180 sequences of soybean aphid in Northeast China including H1 shared by all the populations. Lower haplotype diversity (Hd=0.3590± 0.0420) and nucleotide diversity (Pi=0.0012±0.0002) were observed and high gene flow was detected in every two populations, while most of the variation (80.81%) arose from variability within A. glycines from individuals. Low genetic differentiation and high gene flow (Nm=2.106) indicated a high migration rate between the populations, which might reveal that gene flow in different geographic populations did not affect by geographical distance. The phylogenetic tree and the haplotype network of A. glycines were obtained based on sequences of CO II gene, there were no significant genealogical branches or clusters recognized in NJ tree, and no clear distribution, delineation of haplotypes were demonstrated in the haplotype network according to geographical location. This study rejected the vicariance hypothesis: geographic isolation could be a barrier and it restricted A. glycines gene flow among 10 populations.