SILENCING THE EGYPTIAN COTTON LEAFWORM; Spodoptera littoralis (BIOSD.) CYTOCHROME P450 INHIBITS THE METABOLISM OF GOSSYPOL USING RNAI TECHNIQUE

Abstract

RNA interference is an effective means regulate gene expression in both vitro and vivo. P450 monooxygenase plays a vital role in adaptation to cotton defence compounds such gossypol; toxic to Lepidopteran pests. This gene is highly expressed in insect midgut and its expression correlates with larval growth when gossypol is included in diet. Commonly, the transcription levels of P450 monoxygenase enzymes in the insect midgut are increased in the presence of gossypol compound. The current study is therefore revealed the inhibition effect of siRNA of cytP450 on the Egyptian cotton leafworm; Spodoptera littoralis (Biosd.) by selective targeting of cytochrome P450 gene. Small sequence of siRNA was designed and was subjected to cotton leafworm larvae using two different assays; diet mixing assay and force feeding assay. In diet mixing assay; the larval mortality percentage was ranged between 6.7 to 60% with 20 to 300ng siRNAi/g diet but this mortality showed 23.3 to 53.35 % in force feeding assay respectively 72h after treatment. Also, changes in esterase enzyme level was proved in insect gut (0.08 to 0.19 ng) in treated and untreated larvae when they subjected to diet incorporating 300ng/g siRNAi. Thus, the current investigation revealed that dsRNA used in this study plays as key factor for growth inhibition of cotton leafworm larvae which may consider as pave to develop transgenic cotton plants express siRNAi sequence that could reduce cotton leafworm population without insecticides intervention.