Genome sequencing and assembly of Indian golden silkmoth, Antheraea assamensis Helfer (Saturniidae, Lepidoptera).

Muga silkworm (Antheraea assamensis), one of the economically important wild silkmoths, is unique among saturniid silkmoths. It is confined to the North-eastern part of India. Muga silk has the highest value among the other silks. Unlike other silkmoths, A. assamensis has a low chromosome number (n = 15), and ZZ/ZO sex chromosome system. Here, we report the first high-quality draft genome of A. assamensis, assembled by employing the Illumina and PacBio sequencing platforms. The assembled genome of A. assamensis is 501.18 Mb long, with 2697 scaffolds and an N50 of 683.23 Kb. The genome encompasses 18,385 protein-coding genes, 86.29% of which were functionally annotated. Phylogenetic analysis of A. assamensis revealed its divergence from other Antheraea species approximately 28.7 million years ago. Moreover, an investigation into detoxification-related gene families, CYP450, GST, and ABC-transporter, revealed a significant expansion in A. assamensis as compared to the Bombyx mori. This expansion is comparable to Spodoptera litura, suggesting adaptive responses linked to the polyphagous behavior observed in these insects. This study provides valuable insights into the molecular basis of evolutionary divergence and adaptations in muga silkmoth. The genome assembly reported in this study will significantly help in the functional genomics studies on A. assamensis and other Antheraea species along with comparative genomics analyses of Bombycoidea insects.

Transcriptome analysis of Nosema assamensis infecting muga silkworms (Antheraea assamensis) reveals insights into candidate pathogenicity related genes and molecular pathways required for pathogenesis.

Muga silkworms are often prone to many diseases since, these are non-domesticated and are reared outdoors. Microsporidia, an obligate intracellular pathogen with spore as its active form, causes pebrine disease in these silkworms. The study has attempted to categorise the transcript data of the Nosema obtained from the infected muga silkworm using gene ontology and KEGG pathway studies. A total of 2850 unigene sets were identified out of which 2739 unigenes were placed under biological, cellular as well as molecular function categories based on the gene ontology (GO) terms. 1620 out of these unigenes sets found their orthologous partner in the corresponding Nosema bombycis transcriptome. The unigenes were found to be enriched under organic substance metabolic process, organic cyclic compound binding and intracellular anatomical structure for biological process, molecular function and cellular components respectively. The KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway analysis indicated majority of the enzymes were found to be mapped under purine and thiamine metabolic pathways, indicating an increase in the energy metabolism required to establish the infection in the silkworms. The putative virulence genes identified in this study are PTP2, PTP3, SWP12 and SWP26 which were found to be expressed in other Nosema species indigenous to India, indicating a probable conservation of these genes, which are primarily involved in establishing host pathogen interactions. The expression of these genes was in detectable levels in the infected silkworm samples. These genes may be validated further through bioassay in order understand their roles in establishing the infection and propagation of the spores. The identified virulence genes may be further targeted to develop diagnostic tools for identification of the pathogen at early stages of infection.