RNA Interference of Three Genes of the Unfolded Protein Response: Activating Factor of Transcription 4, Eukaryotic Translation Initiation Factor 2-alpha Kinase, and Inositol-Requiring Enzyme 1 in Acyrthosiphon pisum.

The Activating Transcription Factor 4 (ATF4) is a transcription factor that can act as both an activator and repressor and is a critical component of the Unfolded Protein Response (UPR) and Amino Acid Response (AAR) pathways. Inositol-requiring enzyme 1 (IRE1) is an Endoplasmic Reticulum (ER) membrane bound kinase/endoribonuclease that functions as a sensor of unfolded protein and is the most conserved component of the UPR in eukaryotes. Eukaryotic Initiation Factor-2-alpha Kinase (PERK) is an ER membrane bound kinase that phosphorylates eukaryotic initiation factor upon activation of the UPR causing downregulation of protein synthesis. It was hypothesized that introduction of double stranded RNA (dsRNA) complementary to each of the target genes to aphid diet may correlate with a change in expression of each gene. The objective of this study was to determine the possible relationship between fed dsRNA concentration and aphid survival. Increase in concentration of ATF4 dsRNA in artificial diet was correlated to a decrease in survival of fed aphids. Greater concentrations of fed dsRNA were associated with less expression of ATF4 mRNA in whole aphids. Increase in concentration of IRE1 and PERK dsRNAs in artificial diet were not correlated to a decrease in survival of fed aphids, although increase in concentrations of the respective dsRNAs were associated with less expression of the target gene mRNAs. These results suggest that target mRNA expression appears to be influenced by concentration of fed dsRNA. The results of this study also indicate that decrease in ATF4 expression is associated with decreased insect survival while decrease in IRE1 and PERK expression is not.