ABSTRACT
The cotton bollworm, Helicoverpa armigera, is a highly polyphagous pest, causing enormous losses to variouseconomically important crops. The identification and in vitro functional validation of target genes of a pest is aprerequisite to combat pest via host-mediated RNA interference (RNAi). In the present study, six hormonalbiosynthesis genes of H. armigera were chosen and evaluated by feeding insect larvae with dsRNAs corresponding to each target gene, viz., juvenile hormone acid methyltransferase (HaJHAMT), prothoracicotropichormone (HaPTTH), pheromone biosynthesis-activating peptide (HaPBAP), molt regulating transcription factor(HaHR3), activated protein 4 (HaAP-4) and eclosion hormone precursor (HaEHP). The loss of function phenotypes for these hormonal genes were observed by releasing second instar larvae on to artificial diet containingtarget gene-specific dsRNAs. Ingestion of dsRNAs resulted in mortality ranging from 60% to 90%, reduced larvalweight, phenotypic deformities and delayed pupation. The quantitative real-time PCR (qRT-PCR) analysisshowed that the target gene transcript levels were decreased drastically (31% to 77%) as compared to control orunrelated control (GFP-dsRNA), and correlated well with the mortality and developmental defects of larvae.Also, a comparison of the silencing efficacy of un-diced long HaPTTH-dsRNA with RNase III diced HaPTTHdsRNA (siRNAs) revealed that long dsRNAs were more efficient in silencing the target gene. These resultsindicated that the hormonal biosynthesis genes have varied sensitivity towards RNAi and could be the vital targetsfor insect resistance in crop plants like cotton which are infested by H. armigera
ABSTRACT
Ensuring agricultural food security is a major concern for the future world, and being the second mostconsumed crop, rice yield needs an urgent upliftment. Grain yield is a pleiotropic trait that employs a plethoraof genes functioning in complex signalling cascades. The yield related genes are controlled by variousregulatory factors including the microRNAs (miRNAs), the small 20–22 nucleotide (nt) non-coding RNAs,which have emerged as the master ribo-regulators of eukaryotic genes. Plant miRNAs can bind to highlycomplementary sequences in the target messenger RNAs (mRNAs) and negatively regulate gene expression tocoordinate the various biological processes involved in plant development. In rice, an ideal plant architecture(IPA) has been regarded as the key to attain high yield and several miRNAs have been deciphered to playimportant roles in orchestrating vital regulatory procedures for achieving optimum plant morphological yieldrelated traits like less unproductive tillers, more panicle branches and heavier grains. In this review, we presentand discuss the various genetic engineering strategies undertaken to manipulate the miRNA-mRNA expressionlevels in order to achieve improved grain output by modulation of rice plant architecture and recent advancesmade in this regard