AUTHOR=Lu Jing-Wen , Jin Liang , Li Meng-Ge , Yu Bryan Q. , Wen Yang-Fan , Gu Yu-Qing , Lin Yi , Yu Xiao-Qiang 

TITLE=A possible mechanism of Cry7Ab4 protein in delaying pupation of Plutella xylostella larvae

JOURNAL=Frontiers in Immunology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2022.849620

DOI=10.3389/fimmu.2022.849620

ISSN=1664-3224

ABSTRACT=<p>Cry toxins produced by <italic>Bacillus thuringiensis</italic> (Bt) are well known for their insecticidal activities against Lepidopteran, Dipteran, and Coleopteran species. In our previous work, we showed that trypsin-digested full-length Cry7Ab4 protoxin did not have insecticidal activity against <italic>Plutella xylostella</italic> larvae but strongly inhibited their growth. In this paper, we expressed and purified recombinant active Cry7Ab4 toxic core from <italic>Escherichia coli</italic> for bioassay and identified its binding proteins. Interestingly, Cry7Ab4 toxic core exhibited activity to delay the pupation of <italic>P. xylostella</italic> larvae. Using protein pull-down assay, several proteins, including basic juvenile hormone-suppressible protein 1-like (BJSP-1), were identified from the midgut juice of <italic>P. xylostella</italic> larvae as putative Cry7Ab4-binding proteins. We showed that feeding <italic>P. xylostella</italic> larval Cry7Ab4 toxic core upregulated the level of BJSP-1 mRNA in the hemocytes and fat body and decreased the free juvenile hormone (JH) level in larvae. BJSP-1 interacted with Cry7Ab4 and bound to free JH <italic>in vitro</italic>. A possible mechanism of Cry7Ab4 in delaying the pupation of <italic>P. xylostella</italic> larvae was proposed.</p>