Cysteine protease enhances plant-mediated bollworm RNA interference

Area of Science:

• Plant-insect interactions
• Molecular entomology
• RNA interference (RNAi)

Background:

• Oral ingestion of plant-expressed double-stranded RNA (dsRNA) induces target gene suppression in insects.
• The insect peritrophic matrix (PM) acts as a barrier, hindering dsRNA transmission to midgut cells.
• Plant cysteine proteases are being investigated for their role in modulating insect physiology.

Purpose of the Study:

• To investigate the effect of plant cysteine proteases on the insect peritrophic matrix.
• To determine if cysteine proteases enhance plant-mediated RNA interference (RNAi) in insects.
• To evaluate the combined efficacy of cysteine proteases and dsRNA in plant defense strategies.

Main Methods:

• Cotton bollworm larvae (Helicoverpa armigera) were fed plant cysteine proteases (GhCP1, AtCP2).
• Peritrophic matrix permeability was assessed in pre-fed larvae.
• Larvae were exposed to toxins (gossypol) and dsRNA-expressing plants (dsCYP6AE14), with and without protease pre-feeding.

Main Results:

• Ingestion of plant cysteine proteases attenuated the peritrophic matrix in cotton bollworm larvae.
• Protease pre-feeding increased gossypol accumulation and susceptibility to a dsRNA virus (DpCPV).
• Enhanced RNAi effects were observed in larvae fed dsRNA-expressing plants after protease pre-feeding.
• Cotton plants co-expressing dsCYP6AE14 and GhCP1 showed improved resistance to bollworm feeding compared to single-transgene lines.

Conclusions:

• Plant cysteine proteases can increase peritrophic matrix permeability in herbivorous insects.
• This increased permeability enhances the efficacy of plant-mediated RNAi and toxin delivery.
• Combining cysteine proteases with dsRNA in plants offers a promising strategy for improved insect pest control.