1 INTRODUCTION
The Japanese giant silkworm, Caligula japonica (Moore 1872)
(Lepidoptera: Bombycoidea), is generally considered as a forestry pest
due to its damage to many trees, particular for walnut tree (Chenet al ., 2021a). It is widely distributed in Asian, and its damage
caused huge economic loss every year in Japan, North Korea, Russia, and
especially as to China. However, recent research indicated that the
cocoon of pupa (Figure 1) displays nontoxicity, biocompatibility,
suitable mechanical properties, and porosity while showing no adverse
effect in animal trials and even appears to enhance cell proliferation,
so it could be used as natural medical mesh in the medical industry
(Chen et al. , 2022). While the genetical mechanism of this
compatibility are completely unexplored. There are two types of diapause
for C. japonica . It overwinters with egg diapause. The egg period
lasts until the middle of May of the next year and pupates from the
middle of July. The pupal period is about 40 days, which shows summer
diapause (Chen et al. , 2021b). Diapause of insects is common, but
it is rare for a species to have two diapause modes. At molecular level,
the regulation mechanism related to diapause C. japonica have
remained unknown. To more in-depth research on regulation of diapause
and exert its potential medical value of C. japonica , a
high-quality genome is an essential tool.
As a miniature animal group on the earth, insects have evolved a variety
of strategies to resist unfit environment to survive, among that
diapause is a very effective strategy. The regulation of insect diapause
involves many factors, such as the induction of abiotic factors,
photoperiod, temperature, and humidity. Both long and short light can
induce insects to enter diapause, For instance, Mamestra
brassicae will enter summer diapause when the illumination is
> 12h (Goto and Hukushima, 1995); Chilo suppressaliswill enter winter diapause when the illumination is less than 12h (Xiaoet al. , 2010). While the regulation of hormones and some
foundational proteins are always inseparable as biological factor
(Denlinger, 2002). Studies have shown that Ecdysone, juvenile hormone,
prothoracic tropic hormone (PTTH) and some rhythm genes,including
diapause hormone (DH ), period (per ) , timeless
(tim ) , Cryptochrome 1(CRY 1 ), Cryptochrome 2(CRY
2 ), can affect the diapause of insects (Denlinger, 1985). Nevertheless,
it is poorly understood how rhythm genes regulate diapause of C.
japonica .
The high-quality genome can help to explore the new function of key
genes in insect physiological regulation and searching for new metabolic
pathways. Here, to better study the diapause mechanism and explore the
genetic of C. japonica ,
we
conducted high-throughput sequencing of its genome and obtained
high-quality chromosome level genome. The rhythm genes closely related
to diapause were annotated manually. We provide a helpful genome
sequence resources for in-depth investigations for insect diapause and
forward research on C. japonica .