Study On The Interaction Of Bacillus Thuringiensis Crystal Protein Cry6A And Caenorhabditis Elegans

Parasporal crystal protein produced by Bacillus thuringiensis(Bt) is the most widely used microbial insecticide. Cry6 A is a group of nematicidal crystal protein with novel topology structure, which exhibits diverse nematicidal property. When attacked by Cry6 A crystal protein toxin, nematode may take a variety of defense strategy to protect itself. In our previous study,many differentially expressed proteins have been observed from C. elegans intoxicated by Cry6 A toxin through proteomics technology. In this research,the functions of the differentially expressed proteins in the defense response of C. elegans toward Cry6 A toxin were studied.Our result showed that, Cry6 A toxin obviously promoted the energy metabolism of C. elegance. When worm was intoxicated by Cry6 A toxin, the expression levels of several crucial enzymes in energy metabolism pathway increased obviously. For example, the abundance of arginine kinase and pyruvate dehydrogenase were enhanced by 1.53-fold and 1.92-fold,respectively. Due to the increase of energy production, ATP was observed to be enhanced by 6.67-fold from C. elegans after intoxication of Cry6 A toxin.When nematode is under the condition of toxin stress, the energy metabolism level was enhanced to meet the need of immune defense response, and then provides protection for nematode from the intoxication by Cry6 A crystal protein toxin.Cry6A crystal protein toxin significantly enhances the expression level of DIM-1, which functions in nematode locomotion. After intoxication by Cry6 A toxin, the motilities of wild-type N2 and DM2(movement protein gene dim-1mutant strain of C.elegans) were all obviously inhibited. Motility track analysis indicated that the wavelength and amplitude of DM2 path decreased more obviously than those of N2, which indicates that the mutant strain DM2 is more sensitive to Cry6 A toxin than N2 on the impact of motility. The greatersusceptibility of DM2 to Cry6 A toxin is due to the deficiency of DIM-1. When attacked by Cry6 A toxin, nematode may provide protection for itself by enhancing the expression level of DIM-1 to recover its locomotion ability,which proved that DIM-1 plays key role in the defense response of nematode to Cry6 A crystal protein toxin.The expression levels of several proteins related to worm lifespan were significantly changed by intoxication of Cry6 A crystal protein toxin, such as DAF-2, DAF-16, PUD1, and PUD2. In the presence of Cry6 A the lifespan of N2 strain shortened significantly. Meanwhile, the mutant strains CF1442(daf-2/daf-16)and CB1370(daf-2)exhibited more sensitive to Cry6 A toxin compared with wild-type strain N2. These results implied that daf-2 and daf-16 protect nematode from Cry6 A toxin through regulating its lifespan, thereby play important role in worm defense response.In conclusion, this study showed that C.elegans may trigger diverse defense responses to protect itself when it is challenged by Cry6 A crystal protein toxin, such as increase of energy metabolism level to promote immune response, remediation of locomotion ability, and regulation of lifespan, which revealed a very delicate network of defense response in C. elegans. Moreover,all these results gave us give an important insight into studying the resistance of nematode to pathogens, and facilitate us to further understand the survival mechanism in nature conditions, and in-depth understand the ecology of C.elegnas, the model organism.