Sex Determination in Beetles: Production of All Male Progeny by Parental RNAi Knockdown of Transformer

Sex in insects is determined by a cascade of regulators ultimately controlling sex-specific splicing of a transcription factor, Doublesex (Dsx). We recently identified homolog of dsx in the red flour beetle, Tribolium castaneum (Tcdsx). Here, we report on the identification and characterization of a regulator of Tcdsx splicing in T. castaneum. Two male-specific and one female-specific isoforms of T. castaneum transformer (Tctra) were identified. RNA interference-aided knockdown of Tctra in pupa or adults caused a change in sex from females to males by diverting the splicing of Tcdsx pre-mRNA to male-specific isoform. All the pupa and adults developed from Tctra dsRNA injected final instar larvae showed male-specific sexually dimorphic structures. Tctra parental RNAi caused an elimination of females from the progeny resulting in production of all male progeny. Transformer parental RNAi could be used to produce all male population for use in pest control though sterile male release methods

Doublesex Target Genes in the Red Flour Beetle, Tribolium castaneum

Sex determination cascade in insects terminates with the production of sex-specific protein, Doublesex (Dsx). We identified the dsx homolog (Tcdsx) in Tribolium castaneum. The pre-mRNA of Tcdsx is sex-specifically spliced into three female (Tcdsxf1, Tcdsxf2 and Tcdsxf3) and one male-specific (Tcdsxm) isoforms. Cis-regulatory elements potentially involved in sex-specific splicing of the Tcdsx pre-mRNA were identified in the female-specific exon and the adjoining intronic sequences. All the three female-specific TcDsx proteins share common OD1 and OD2 domains and differ in their C-terminal sequences. Knockdown of Tcdsx resulted in a reduction in the oocyte development, egg production and hatching of eggs laid. Several genes, including those coding for Vitellogenins and Vitellogenin receptors were identified as targets of TcDsx. RNAi experiments showed an isoform-specific targeting of identified target genes by TcDsx as knockdown in the expression of Tcdsx isoforms individually or in combinations resulted in differential effects on the expression of target genes

Novel female-specific splice form of dsx in the silkworm, Bombyx mori

The Bombyx mori doublesex (Bmdsx), a homologue of doublesex of Drosophila, is the bottom most gene of the sex determination cascade. Bmdsx plays a very crucial role in somatic sexual development. Its pre-mRNA sex-specifically splices to generate two splice variants; one encodes female-specific and the other encodes male-specific polypeptides which differ only at their C-termini. The open reading frame of Bmdsx consists of 5 exons, of which exons 3 and 4 are female-specific and are skipped in males. In the present study, we have identified a third splice form of the Bmdsx which is specific only to females and differs from the previously reported Bmdsxf isoform by the presence of 15 bp sequence. This new female splice form is generated as a result of alternative 5' splice site selection in the third exon adding additional 15 bp sequence in exon 3 which results in alteration of the reading frame leading to incorporation of an early stop codon. Thus the protein encoded by this splice form is 20 aa shorter than the known BmDsxF. Initial results obtained from the study of dsx homologues in Saturniid silkmoths suggest that both the female-specific Dsx proteins are essential for female sexual differentiation. It remains to be seen whether female-specific multiple splice forms of dsx are characteristic feature of only silkmoths or widespread among lepidopterans. The findings that sex determination mechanism is unique in lepidopterans offer an opportunity to develop genetic sexing methods in beneficial as well as economically destructive lepidopteran pests

Comparative Analysis of Double-Stranded RNA Degradation and Processing in Insects

RNA interference (RNAi) based methods are being developed for pest management. A few products for control of coleopteran pests are expected to be commercialized soon. However, variability in RNAi efficiency among insects is preventing the widespread use of this technology. In this study, we conducted research to identify reasons for variability in RNAi efficiency among thirty-seven (37) insects belonging to five orders. Studies on double-stranded RNA (dsRNA) degradation by dsRNases and processing of labeled dsRNA to siRNA showed that both dsRNA degradation and processing are variable among insects belonging to different orders as well as among different insect species within the same order. We identified homologs of key RNAi genes in the genomes of some of these insects and studied their domain architecture. These data suggest that dsRNA digestion by dsRNases and its processing to siRNAs in the cells are among the major factors contributing to differential RNAi efficiency reported among insects

Unique Features of a Global Human Ectoparasite Identified Through Sequencing of the Bed Bug Genome

The bed bug, Cimex lectularius, has re-established itself as a ubiquitous human ectoparasite throughout much of the world during the past two decades. This global resurgence is likely linked to increased international travel and commerce in addition to widespread insecticide resistance. Analyses of the C. lectularius sequenced genome (650 Mb) and 14,220 predicted protein-coding genes provide a comprehensive representation of genes that are linked to traumatic insemination, a reduced chemosensory repertoire of genes related to obligate hematophagy, host-symbiont interactions, and several mechanisms of insecticide resistance. In addition, we document the presence of multiple putative lateral gene transfer events. Genome sequencing and annotation establish a solid foundation for future research on mechanisms of insecticide resistance, human-bed bug and symbiont-bed bug associations, and unique features of bed bug biology that contribute to the unprecedented success of C. lectularius as a human ectoparasite

Molecular Evolutionary Trends and Feeding Ecology Diversification in the Hemiptera, Anchored by the Milkweed Bug Genome

Background: The Hemiptera (aphids, cicadas, and true bugs) are a key insect order, with high diversity for feeding ecology and excellent experimental tractability for molecular genetics. Building upon recent sequencing of hemipteran pests such as phloem-feeding aphids and blood-feeding bed bugs, we present the genome sequence and comparative analyses centered on the milkweed bug Oncopeltus fasciatus, a seed feeder of the family Lygaeidae. Results: The 926-Mb Oncopeltus genome is well represented by the current assembly and official gene set. We use our genomic and RNA-seq data not only to characterize the protein-coding gene repertoire and perform isoform-specific RNAi, but also to elucidate patterns of molecular evolution and physiology. We find ongoing, lineage-specific expansion and diversification of repressive C2H2 zinc finger proteins. The discovery of intron gain and turnover specific to the Hemiptera also prompted the evaluation of lineage and genome size as predictors of gene structure evolution. Furthermore, we identify enzymatic gains and losses that correlate with feeding biology, particularly for reductions associated with derived, fluid nutrition feeding. Conclusions: With the milkweed bug, we now have a critical mass of sequenced species for a hemimetabolous insect order and close outgroup to the Holometabola, substantially improving the diversity of insect genomics. We thereby define commonalities among the Hemiptera and delve into how hemipteran genomes reflect distinct feeding ecologies. Given Oncopeltus’s strength as an experimental model, these new sequence resources bolster the foundation for molecular research and highlight technical considerations for the analysis of medium-sized invertebrate genomes

Unique features of a global human ectoparasite identified through sequencing of the bed bug genome

The bed bug, Cimex lectularius, has re-established itself as a ubiquitous human ectoparasite throughout much of the world during the past two decades. This global resurgence is likely linked to increased international travel and commerce in addition to widespread insecticide resistance. Analyses of the C. lectularius sequenced genome (650 Mb) and 14,220 predicted protein-coding genes provide a comprehensive representation of genes that are linked to traumatic insemination, a reduced chemosensory repertoire of genes related to obligate hematophagy, host–symbiont interactions, and several mechanisms of insecticide resistance. In addition, we document the presence of multiple putative lateral gene transfer events. Genome sequencing and annotation establish a solid foundation for future research on mechanisms of insecticide resistance, human–bed bug and symbiont–bed bug associations, and unique features of bed bug biology that contribute to the unprecedented success of C. lectularius as a human ectoparasite

Brunt of COVID-19 Pandemic on Medics’ Children

COVID-19 has created many changes in the social norms; children being an obvious part of society are also not exempted from this. Not only their studies have been affected, but also their behaviour has been found to be altered. They are facing many different types of attitudes from their own parents, classmates, friends and society during this COVID scenario. This study was conducted to assess the behavioural changes in the children of medical professionals due to the apprehension caused by the corona infection and stress generated by the same

Long Non-Coding RNAs in Insects

Only a small subset of all the transcribed RNAs are used as a template for protein translation, whereas RNA molecules that are not translated play a very important role as regulatory non-coding RNAs (ncRNAs). Besides traditionally known RNAs (ribosomal and transfer RNAs), ncRNAs also include small non-coding RNAs (sncRNAs) and long non-coding RNAs (lncRNAs). The lncRNAs, which were initially thought to be junk, have gained a great deal attention because of their regulatory roles in diverse biological processes in animals and plants. Insects are the most abundant and diverse group of animals on this planet. Recent studies have demonstrated the role of lncRNAs in almost all aspects of insect development, reproduction, and genetic plasticity. In this review, we describe the function and molecular mechanisms of the mode of action of different insect lncRNAs discovered up to date