A determining factor for insect feeding preference in the silkworm, Bombyx mori

Area of Science:

• * Insect behavior and genetics
• * Molecular mechanisms of host-plant selection

Background:

• * Insect feeding preference is crucial for adaptation and survival, but its genetic basis remains largely unknown.
• * The domesticated silkworm (Bombyx mori), a monophagous species feeding primarily on mulberry leaves, serves as an excellent model for studying host-plant selection.
• * The molecular mechanisms underlying Bombyx mori's specific feeding preference are not yet understood.

Purpose of the Study:

• * To identify the genetic factors responsible for the mulberry-specific feeding preference in Bombyx mori.
• * To investigate the role of the gustatory receptor gene GR66 in determining insect feeding behavior.

Main Methods:

• * Utilized a transposon-based clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein-9 nuclease (Cas9) system to genetically mutate the GR66 locus.
• * Established homozygous mutant silkworm strains with truncated GR66 proteins.
• * Conducted feeding assays and feeding choice experiments to evaluate the feeding behavior of mutant and wild-type larvae.

Main Results:

• * GR66 mutant silkworm larvae exhibited altered feeding behavior, consuming a variety of plant species beyond mulberry leaves, including fruits and seeds.
• * Mutant larvae demonstrated a loss of specificity for mulberry leaves in feeding choice assays.
• * Genetic mutation of GR66 led to the acquisition of new feeding activities in silkworm larvae.

Conclusions:

• * The study provides the first genetic and phenotypic evidence that a single bitter gustatory receptor (GR), GR66, is a major determinant of insect feeding preference.
• * GR66 plays a critical role in the mulberry-specific feeding behavior of Bombyx mori.
• * Findings offer insights into the molecular basis of host-plant selection in insects.