The mitogen-activated protein kinase p38 is involved in insect defense against Cry toxins from Bacillus thuringiensis

The insecticidal Cry toxins are pore-forming toxins produced by the bacteria Bacillus thuringiensis that disrupt insect-midgut cells. In this work we analyzed the response of two different insect orders, the Lepidopteran Manduca sexta and Dipteran Aedes aegypti to highly specific Cry toxins, Cry1Ab and Cry11Aa, respectively. One pathway activated in different organisms in response to a variety of pore-forming toxins is the mitogen-activated protein kinase p38 pathway (MAPK p38) that activates a complex defense response. We analyzed the MAPK p38 activation by immunodetection of its phosphorylated isoform, and the induction of p38 by RT-PCR, real-time PCR quantitative assays and immunodetection. We show that MAPK p38 is activated at postraductional level after Cry toxin intoxication in both insect orders. We detected the p38 induction at the transcriptional and traductional level, and observed a different response. In these three levels, we found that both insects respond to Cry toxin action but M. sexta responses more strongly than A. aegypti. Gene silencing of MAPK p38 in vivo, resulted in both insect species becoming hypersensitive to Cry toxin action, suggesting that the MAPK p38 pathway is involved in insect defense against Bt Cry toxins. This finding may have biotechnological applications for enhancing the activity of some Bt Cry toxins against specific insect pests.