Exploring systemic RNA interference in insects: a genome-wide survey for RNAi genes in Tribolium

Abstract

Background: RNA interference (RNAi) is a highly conserved cellular mechanism. In some organisms, such as Caenorhabditis elegans, the RNAi response can be transmitted systemically. Some insects also exhibit a systemic RNAi response. However, Drosophila, the leading insect model organism, does not show a robust systemic RNAi response, necessitating another model system to study the molecular mechanism of systemic RNAi in insects.

Diet-delivered RNAi in Helicoverpa armigera – Progresses and challenges

“…T. castaneum (Tomoyasu et al, 2008). The same study surmised that secondary amplification in T. castaneum is likely based on a different gene with similar activity to RdRp or another mechanism entirely.…”

“…The presence of at least 2 sid-1 homologs in H. armigera has been reported (unpublished data, Xue et al (2012)), but analysis of published insect genomes thus far has not produced clear correlation between the presence of sid-1 homologs and systemic RNAi response in insects (Tomoyasu et al, 2008). Sid-1 homologs have been shown to be dispensable with regard to the robust systemic RNAi observed in Locusta migratoria (Luo et al, 2012) and T. castaneum (Tomoyasu et al, 2008). Furthermore, homologs of genes necessary for systemic RNAi in C. elegans have also been found to be absent in T. castaneum (Tomoyasu et al, 2008), which suggests the existence of an alternative mechanism for systemic RNAi in insects.…”

“…Sid-1 homologs have been shown to be dispensable with regard to the robust systemic RNAi observed in Locusta migratoria (Luo et al, 2012) and T. castaneum (Tomoyasu et al, 2008). Furthermore, homologs of genes necessary for systemic RNAi in C. elegans have also been found to be absent in T. castaneum (Tomoyasu et al, 2008), which suggests the existence of an alternative mechanism for systemic RNAi in insects.…”

Use of chromatin remodeling ATPases as RNAi targets for parental control of western corn rootworm (Diabrotica virgifera virgifera) and Neotropical brown stink bug (Euschistus heros)

“…Frequently, homozygous mutant offspring of a heterozygous mother can survive to adulthood using the mother's deposit of RNA or protein in the egg; in fruit flies the essential function of such genes can be assessed by germline mutant clones (Perrimon, 1998). Since it is believed that the RNAi effect is not amplified in insects (Roignant et al, 2003;Tomoyasu et al, 2008), pRNAi may more effectively target the finite mRNA load from the mother. Hence, genes that have essential maternal contribution of mRNA are likely to offer more sensitive pRNAi targets.…”

Knowledge-based discovery for designing CRISPR-CAS systems against invading mobilomes in thermophiles

“…RNA-directed defense mechanisms in the genomes of thermophilic bacteria and archaea have evolved like a prokaryotic genome to cope with the constant threat of genome invaders (Chellapandi and Ranjani 2011;Makarova et al 2012;Weinberger et al 2012;Vestergaard et al 2014). The existence of this pathway in these genomes has been hypothesized to parallel the eukaryotic RNAi pathway known as Clustered regularly interspaced short palindromic repeats-CRISPR-associated sequences (CRISPR-CAS) system or prokaryotic RNAi (pRNAi) (Lillestol et al 2006;Makarova et al 2006;Tomoyasu et al 2008). The common structural characteristics of CRISPR loci are: (1) multiple short direct repeats (2) non-repetitive spacer sequences between the repeats of similar size (3) a common leader sequence of a few hundred base pairs harboring multiple CRISPR loci and (4) accompanied by cas gene families.…”