A strong promoter of a non-cry gene directs expression of the cry1Ac gene in Bacillus thuringiensis
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Bacillus thuringiensis bacteria show insecticidal activities that rely upon the production of insecticidal crystal proteins, which are encoded by cry or cyt genes and can target a variety of insect pests. It has been shown that cry1Ac is the only cry gene in B. thuringiensis subsp. kurstaki HD73 (B. thuringiensis HD73) and its expression is controlled by both σE and σK. Here, we report a novel σE-dependent strong promoter of a non-cry gene (HD73_5014), which can direct strong cry1Ac gene expression in B. thuringiensis HD73. We constructed an E. coli-B. thuringiensis shuttle vector (pHT315-P 5014 -1Ac) for cry1Ac gene expression, using the HD73_5014 gene promoter. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and western blot analysis showed that expression of the cry1Ac gene directed by the HD73_5014 gene promoter was at the same level as that directed by the previously known strongest cry promoter, P cry8E . However, this strain did not form typical bipyramidal crystals in mother cells, as observed by transmission electron microscopy and atomic force microscope. The strain with Cry1Ac protein expression under the control of the HD73_5014 gene promoter (P 5014 -cry1Ac) showed insecticidal activity against Plutella xylostella similar to that under the control of the orf1cry8E gene promoter (P cry8E -cry1Ac). Collectively, these results suggest that the HD73_5014 gene promoter, as a non-cry gene promoter, would be an efficient transcriptional element for cry gene expression. These data also show the possibility for improving Cry production by searching for transcriptional elements in not only cry genes, but also non-cry genes.
KeywordsNon-cry gene promoter P5014 cry1Ac Bacillus thuringiensis
We thank F He (CAAS) and X Tian (CAAS) for participating in some of the work, S Huang (CAAS) for providing technical support in preparing the AFM pictures, and X Chen (CAAS) and Y Xiao (CAAS) for some experimental performances.
XZ, JZ, DS, and FS designed the experiments. XZ performed the experiments. TG, QP, and FS analyzed the results. LS analyzed the RNA-Seq data. TG, YC, and FS wrote the manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
This article does not contain any studies with human participants or animals performed by any of the authors
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