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

Abstract

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 immunodection. 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.

Single amino acid mutation in an ATP-binding cassette transporter gene causes resistance to Bt toxin Cry1Ab in the silkworm, Bombyx mori

“…Glycosyltransferase genes of B. mori were PCR-amplified, cloned, and sequenced by using newly designed primers (Bre primers in SI Appendix, Table S2). None of the genes for cadherin-like peptide (16), aminopeptidases (17,18), glycosyltransferases (Bre-2-5) (19,20), alkaline phosphatase (21), chlorophyllide-binding protein (22), α-amylase (23), or MAPK p38 (24) were located on chromosome 15 (SI Appendix, Table S3), indicating the presence of a different form of Bt resistance in strain C2.…”

Molecular characterization and immunohistochemical localization of a mitogen-activated protein kinase, Accp38b, from Apis cerana cerana

“…These results suggest that the function of p38 MAPKs in insects is conserved. Recently, the p38 MAPK from Drosophila was reported to participate in the defense response against Cry toxins from Bacillus thuringiensis, pathogenic bacteria and fungi (10,18). This observation provides clues for the role of Accp38b in the defense response; however, it should be further explored.…”

Role of Pore-Forming Toxins in Bacterial Infectious Diseases

“…With the exception of membrane repair mechanisms, which have not been determined clearly in vivo except for in C. elegans (330), all of these mechanisms were also identified in vivo in 1 or more of the 10 pathogens discussed here (Table 2). A role in PFT defense, or at least PFTdependent activation, was seen for MAPKs with S. pneumoniae PLY (p38) (390), GBS ␤-h/c (p38 and JNK) (361), B. anthracis ALO (p38 and ERK) (34), and B. thuringiensis Cry toxins (p38 and JNK) (231,313). A role for the inflammasome was observed for S. pneumoniae PLY (357,363), S. aureus alpha-toxin (366), and possibly GAS SLO (365) and L. monocytogenes LLO (362).…”