Egg Cooling After Oviposition Extends the Permissive Period for Microinjection-Mediated Genome Modification in .

In general, transgenesis efficiency is largely dependent on the developmental status of eggs for microinjection. We investigated whether the relationship between transgenesis efficiency and cooling eggs in silkworms, , affects the transgenesis frequencies. First, we performed a microinjection using eggs of different developmental statuses at 25 °C.

Fibroin heavy chain gene replacement with a highly ordered synthetic repeat sequence in Bombyx mori.

The exceptional quality of silkworm silk is attributed to the amino acid sequence of its fibroin heavy chain (Fib-H) protein. The large central domain of Fib-H, which consists of glycine- and alanine-rich crystalline regions interspersed with amorphous motifs of approximately 30 amino acid residues, is considered crucial for fibrilization and determines the properties of the silk fiber. We established a technical platform to modify the Fib-H core region systematically using transcription activator-like effector nuclease-mediated homologous recombination through a somatic and germline gene knockin assay along with PCR-based screening.

Abolition of egg diapause by ablation of suboesophageal ganglion in parental females is compatible with genetic engineering methods.

Microinjection of genetic material into non-diapause eggs is required for genetic engineering of silkworms. Besides diapause could be useful for maintaining transgenic lines, a drawback of this technology is that most standard silkworm strains and experimental lines of interest produce diapausing eggs. Several approaches have been developed to abolish diapause but none are very efficient.

Myosuppressin is involved in the regulation of pupal diapause in the cabbage army moth Mamestra brassicae.

Diapause, a programmed developmental arrest, is common in insects, enabling them to survive adverse seasons. It is well established that pupal diapause is regulated by ecdysteroids secreted by the prothoracic glands (PGs), with cessation of ecdysteroid secretion after pupal ecdysis leading to pupal diapause. A major factor regulating the gland activity is prothoracicotropic hormone (PTTH) secreted from the brain.

Endocrine Mechanisms Regulating Post-Diapause Development in the Cabbage Armyworm, Mamestra brassicae.

Diapause, a programmed developmental arrest at a specific stage, is common in insects and is regulated by hormones. It is well established that in pupal diapause, cessation of ecdysteroid secretion from the prothoracic glands (PGs) after pupal ecdysis leads to diapause initiation, while resumption of its secretion induces post-diapause development. However, what regulates the activity of the glands is poorly understood, especially for the glands of diapause-terminated pupae.

Prothoracicotropic hormone acts as a neuroendocrine switch between pupal diapause and adult development.

Diapause is a programmed developmental arrest that has evolved in a wide variety of organisms and allows them survive unfavorable seasons. This developmental state is particularly common in insects. Based on circumstantial evidence, pupal diapause has been hypothesized to result from a cessation of prothoracicotropic hormone (PTTH) secretion from the brain.