1 INTRODUCTION
The rose-grain aphid Metopolophium dirhodum (Walker) (Hemiptera:
Aphididae) is one of the most common and economically important aphid
pests for cereals, including wheat, barley, rye and oat, worldwide
(Cannon, 1986; Honek, 1991; Ma et al., 2004; Li et al., 2020). M.
dirhodum is native in the Holarctic and was then introduced to North
America, South America, South Africa, Europe, Oceania and Eastern Asia
(Honek et al., 2018; Blackman and Eastop, 2000). In the continental
climate of central Europe, M. dirhodum is usually the most
abundant aphid species on cereals (Honek et al., 1987, 2018; Praslicka
et al., 1996).
Damage caused to cereals by M. dirhodum takes several forms.
These include sucking the juice from wheat leaves, stems and young ears,
which further results in the deterioration of plant nutrition (Holt et
al., 1984), defecating sticky honeydew that further obstructs
photosynthesis and reduces wheat quality (Jiang et al., 2019), and
transmission of a number of pathogenic plant viruses, including the
barley yellow dwarf virus (Kennedy et al., 2005). Both nymphs and adults
of this aphid may cause yield losses of 27–30% during the latter part
of flowering stages of wheat (Holt et al., 1984; Chopa et al., 2012).
Recently, several studies have
focused on the population dynamics (Honek et al., 2018), control methods
(Cambier et al., 2001; Chopa et al., 2012) and symbiotic microorganisms
(Telesnicki et al., 2012) of M. dirhodum . However, the challenge
to developing a further understanding is the lack of genomic resources
for this pest. To date, chromosome-level genomes with annotation
information for several aphid species, including Acyrthosiphon
pisum (International Aphid Genomics Consortium., 2010), Sitobion
miscanthi (Jiang et al., 2019), Eriosoma lanigerum (Mathers et
al., 2021) and Rhopalosiphum maidis (Chen et al., 2019), are
available, which will be very helpful for the further study of these
aphids. Here, we report the genome sequence of M. dirhodumassembled by incorporating Pacific Biosciences (PacBio) long HiFi reads
and Hi-C technology. Subsequently, gene prediction, functional
annotation and phylogenetic analysis were also performed. The genomic
resource developed here for M. dirhodum is valuable for
understanding its genetics, development and evolution and will provide
an important reference for the study of other insect genomes.
M. dirhodum , like most aphids, can produce wing morphs when
experiencing crowding, poor nutrition and temperature or photoperiod
changes (Müller et al., 2001; Braendle et al., 2006; Zhang et al.,
2019). Wing dimorphism in insects
is an adaptive switch to environmental changes. Specifically, wingless
morphs allocate more resources to reproduction, enabling rapid colony
growth. Winged morphs are devoted to dispersal, which enables them to
look for new habitats and food resources. Moreover, winged morphs are
better at long-distance migration and host alternation, thus causing
more serious host damage and virus transmission (Zhang et al., 2019).
Therefore, understanding the molecular mechanisms of M. dirhodumin triggering wing dimorphism is important for its effective control. In
the present study, we constructed and sequenced RNA libraries of winged
and wingless M. dirhodum from third- and fourth-instar nymphs and
adults. Differentially expressed genes between the winged and wingless
populations were analyzed and identified according to the current
assembly of the M. dirhodum genome. The results lay a solid
foundation for further study of the molecular mechanisms of wing
dimorphism in M. dirhodum or other insects.