Vitelogenin

Whitefly (B.tabaci) are small insects common in house plants that have developed resistance to many synthetic pesticides making chemical control difficult.

We are going to conduct bio-control of whitefly by attacking the Vitellogenin receptor protein using RNAi. Vitellogenin improces cell oxidative stress tolerance. Removing the Vitellogenin receptor would cause whitefly to die as a result of accumulated oxidative stress.

Background information:

Whitefly (Bemisia tabaci) is globally considered as a polyphagous agricultural pest that causes severe direct and indirect damage to many crops by feeding and transmitting viruses to plants[1].

Vitellogenin(vg): plays vital role in oocytes and embryo development in insects and Vitellogenin gene is responsible for the reduction of oxidative stress in honeybees. We are planning to clone this gene into yeast to test if it reduces oxidative stress in eukaryotes [2]. The recombinant yeast Pichia pastoris has been described in [3]. Oxidative stress in eukaryotes is casually linked to the production of Carbonyl derivatives, by measuring Carbonyl derivatives concentration; oxidative stress can be quantified [4]. By using RNAi to create yeast without Vitellogenin gene and comparing oxidative stress with the wild type, it shows whether Vitellogenin is suitable to reduce oxidative stress in human cells.

RNAi definition in insects: dsRNA is cleaved by a RNase III, often called Dicer, into 21-25 nt-long short interfering RNA duplexes(siRNA). These siRNAs are incorporated into the RNA-induced silencing complex(RISC); after discarding the passenger strand, the RISC will bind to a homolog mRNA, cutting it and thereby hindering translation[8].

RNAi for the whitefly(B.tabaci) Bio-control via oral route: Regarding to the objective of the Sygenta proposal, biocontrol must be applied in the wild by feeding or targeting the specific pest(B. tabaci) that lives on crops. Thus, injecting RNAi into the body of the pest becomes inapplicable. According to [6], the artificial diet (with/without dsRNA/siRNAs) was filter-sterilized (0.22 μm). A 100 μl diet was sandwiched between the two layers of UV-sterilized parafilm and stretched on the inner surface of the tube cap. The entire process was carried out aseptically. The caps of insects containing tubes were replaced with the diet containing caps and tubes were kept upright. The diet was replaced on alternate days to minimize the possibilities of degradation in test samples and prevent microbial contamination.