Characterization of an Ecdysone Oxidase from (L.) and Its Role in Bt Cry1Ac Resistance.

Understanding the molecular mechanisms underlying insect resistance to (Bt) pesticidal proteins is crucial for sustainable pest management. Here, we found that downregulation of the ecdysone oxidase gene () in the normal feeding stages contributes to increased 20-hydroxyecdysone (20E) titer and mediates resistance to the Bt Cry1Ac toxin. The gene was cloned and its expression was significantly downregulated in the midgut of Bt-resistant and Cry1Ac-selected .

A midgut transcriptional regulatory loop favors an insect host to withstand a bacterial pathogen.

Mounting evidence suggests that insect hormones associated with growth and development also participate in pathogen defense. We have discovered a previously undescribed midgut transcriptional control pathway that modulates the availability of 20-hydroxyecdysone (20E) in a worldwide insect pest (), allowing it to defeat the major virulence factor of an insect pathogen (Bt). A reduction of the transcriptional inhibitor (PxDfd) increases the expression of a midgut microRNA (miR-8545), which in turn represses the expression of a newly identified ecdysteroid-degrading glucose dehydrogenase (PxGLD).

MAPK-mediated transcription factor GATAd contributes to Cry1Ac resistance in diamondback moth by reducing PxmALP expression.

The benefits of biopesticides and transgenic crops based on the insecticidal Cry-toxins from Bacillus thuringiensis (Bt) are considerably threatened by insect resistance evolution, thus, deciphering the molecular mechanisms underlying insect resistance to Bt products is of great significance to their sustainable utilization. Previously, we have demonstrated that the down-regulation of PxmALP in a strain of Plutella xylostella (L.) highly resistant to the Bt Cry1Ac toxin was due to a hormone-activated MAPK signaling pathway and contributed to the resistance phenotype.

MAPK-Activated Transcription Factor PxJun Suppresses Expression and Confers Resistance to Cry1Ac Toxin in (L.).

Deciphering the molecular mechanisms underlying insect resistance to Cry toxins produced by Bacillus thuringiensis (Bt) is pivotal for the sustainable utilization of Bt biopesticides and transgenic Bt crops. Previously, we identified that mitogen-activated protein kinase (MAPK)-mediated reduced expression of the gene is associated with Bt Cry1Ac resistance in the diamondback moth, Plutella xylostella (L.).