Abstract
We report a draft assembly of the genome of Hi5 cells from the lepidopteran insect pest, Trichoplusia ni, assigning 90.6% of bases to one of 28 chromosomes and predicting 14,037 protein-coding genes. Chemoreception and detoxification gene families reveal T. ni-specific gene expansions that may explain its widespread distribution and rapid adaptation to insecticides. Transcriptome and small RNA data from thorax, ovary, testis, and the germline-derived Hi5 cell line show distinct expression profiles for 295 microRNA- and >393 piRNA-producing loci, as well as 39 genes encoding small RNA pathway proteins. Nearly all of the W chromosome is devoted to piRNA production, and T. ni siRNAs are not 2´-O-methylated. To enable use of Hi5 cells as a model system, we have established genome editing and single-cell cloning protocols. The T. ni genome provides insights into pest control and allows Hi5 cells to become a new tool for studying small RNAs ex vivo.
Highlights
Lepidoptera, one of the most species-rich orders of insects, comprises more than 170,000 known species (Mallet J, 2007; ), many of which are agricultural pests
The piRNA pathway has been extensively studied in the dipteran insect Drosophila melanogaster, but no piRNA-producing, cultured cell lines exist for dipteran germline cells
Because lepidopteran cell lines are typically tetraploid (), we conclude that the ~368.2 Mb T. ni genome comprises 28 chromosomes: 26 autosomes plus W and Z sex chromosomes
Summary
Lepidoptera (moths and butterflies), one of the most species-rich orders of insects, comprises more than 170,000 known species (Mallet J, 2007; ), many of which are agricultural pests. One of the largest lepidopteran families, Noctuidae, diverged over 100 million years ago (mya) from the Bombycidae—best-known for the silkworm, Bombyx mori (Rainford JL et al, 2014). Hi5 cells produce abundant microRNAs (miRNAs), small interfering RNAs (siRNAs), and PIWI-interacting RNAs (Kawaoka S et al, 2009) (piRNAs), making them one of just a few cell lines suitable for the study of all three types of animal small RNAs. The most diverse class of small RNAs, piRNAs protect the genome of animal reproductive cells by silencing transposons (Brennecke J et al, 2007; Reuter M et al, 2011). The piRNA pathway has been extensively studied in the dipteran insect Drosophila melanogaster (fruit fly), but no piRNA-producing, cultured cell lines exist for dipteran germline cells. T. ni Hi5 cells grow rapidly without added hemolymph (Hink WF, 1970), are readily transfected, and— unlike the more difficult to grow B. mori BmN4 cells (Iwanaga M et al, 2014), which express germline piRNAs—remain homogeneously undifferentiated even after prolonged culture. In contrast to B. mori, no T. ni genome sequence is available, limiting the utility of Hi5 cells
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
