Research
MicroRNAs in Insect-Pathogen interaction using silkworm as a model
MicroRNAs (miRNAs) are ~22 nucleotides non-coding RNA molecules generated from stem-loop hairpin structures called miRNA precursors (pre-miRNAs) of ~80 nt. miRNA genes are first transcribed from different genomic locations as primary transcripts (pri-miRNAs) by RNA polymerase II (Figure 1). These premiRNAs are then processed by RNAase III enzyme Drosha and exported to cytoplasm with the help of Exportin-5. Another RNAase III enzyme. Dicer cuts these ~80 nt premiRNAs to release ~22 nt mature miRNA. The miRNA binds the RNA-Induced Silencing Complex (RISC), and aligns with the target mRNA. Depending on the level of complementarity between the miRNA and the target sequence, the mRNA can either be translationally repressed (partial) or cleaved (identical). In plants, cleavage appears to be the primary mode of action, while in animals’ translational repression seems to be the key method. Since the first discovery of miRNAs lin-4 and let-7 in Caenorhabditis elegans, miRNA abundance in the genomes of various organisms including insects, plants, higher vertebrates and viruses has been reported.
miRNAs play regulatory role in many cellular and developmental processes like cell division , cell death , hormone secretion, neural development and recent evidences suggest that miRNAs also function as tumour suppressor and oncogene. miRNA as a tool has various applications like elucidating the function of any gene as miRNA/siRNA mediated blocking/knock down, which is not only very efficient in delivery but also have enhanced stability and minimized target effects. Moreover, recently researchers have made miRNA expression profile to classify the cancer in humans in any organism.
Figure 1: Steps involved in the biogenesis of microRNAs
MicroRNAs in immune response
The insect immune mechanism has aroused considerable interest in the recent years. Insects possess an innate immune system that shares many fundamental characteristics with the innate immune response of vertebrates. Insect immune system is characterized by an immediate early activation of prophenoloxidase cascade and a rapid induction of anti-microbial proteins and peptides upon microbial infection.
MicroRNAs have crucial roles in regulating the adaptive as well as the innate immune responses. miRNA mediated gene regulation serve as a defence mechanism against viral infections, thereby providing another layer to the innate immune response. In the present study our main objective is to Identify and characterize miRNAs and their targets involved in the insect-pathogen interaction, which would reveal novel insights into the molecular mechanisms by which miRNAs regulate innate immune responses.
Projects being pursued
- Identification and characterization of miRNAs and their targets in Insects.
- Study the Role of microRNAs in intricate insect-pathogen interactions.
Working group
- Jyoti Singh
- Chandrapal Singh
- Deepa Badrinarayan
- S Annapurna Bhavani
- P Nagamanju
Publications
- Singh J, Nagaraju J (2008) In silico prediction and characterization of microRNAs from red flour beetle (Tribolium castaneum). Insect Molecular Biology.
- Archak S, Nagaraju J (2007) Computational prediction of rice (Oryza sativa) miRNA targets. Genomics, Proteomics and Bioinformatics 5: 196-206.