The corpora allata from adult female Locusta migratoria rapidly metabolise precocene-I to a geometric mixture of dihydrodiols, and simultaneously suffer extensive macromolecular labelling. This could explain the selective cell death which precocenes induce, and focuses attention on the high level of epoxidase in these insect organs.

Lethal metabolism of precocene-I to a reactive epoxide by locust corpora allata

The Hemiptera (aphids, cicadas, and true bugs) are a key insect order, with high diversity for feeding ecology and excellent experimental tractability for molecular genetics. Building upon recent sequencing of hemipteran pests such as phloem-feeding aphids and blood-feeding bed bugs, we present the genome sequence and comparative analyses centered on the milkweed bug Oncopeltus fasciatus, a seed feeder of the family Lygaeidae.

https://link.springer.com/content/pdf/10.1186/s13059-019-1660-0.pdf

Molecular evolutionary trends and feeding ecology diversification in the Hemiptera, anchored by the milkweed bug genome

A key regulatory gene in metamorphosing (holometabolous) insect life histories is the transcription factor broad (br), which specifies pupal development. To determine the role of br in a direct-developing (hemimetabolous) insect that lacks a pupal stage, we cloned br from the milkweed bug, Oncopeltus fasciatus (Of’br). We find that, unlike metamorphosing insects, in which br expression is restricted to the larval–pupal transition, Of’br mRNA is expressed during embryonic development and is maintained at each nymphal molt but then disappears at the molt to the adult. Induction of a supernumerary nymphal stage with a juvenile hormone (JH) mimic prevented the disappearance of br mRNA. In contrast, induction of a precocious adult molt by application of precocene II to third-stage nymphs caused a loss of br mRNA at the precocious adult molt. Thus, JH is necessary to maintain br expression during the nymphal stages. Injection of Of’br dsRNA into either early third- or fourth-stage nymphs caused a repetition of stage-specific pigmentation patterns and prevented the normal anisometric growth of the wing pads without affecting isometric growth or molting. Therefore, br is necessary for the mutable (heteromorphic) changes that occur during hemimetabolous development. Our results suggest that metamorphosis in insects arose as expression of br, which conveys competence for change, became restricted to one postembryonic instar. After this shift in br expression, the progressive changes that occur within the nymphal series in basal insects became compressed to the one short period of morphogenesis seen in the larva-to-pupa transition of holometabolous insects.

https://www.pnas.org/content/pnas/103/18/6925.full.pdf

The pupal specifier broad directs progressive morphogenesis in a direct-developing insect

Detoxification of plant toxins by insects

Publisher Summary This chapter explains the corpus allatum of the adult and discusses the control and determination of the normal function of the corpus allatum. The normal secretory function is ensured only when the integrity of the central nervous system—the corpus allatum complex—is unbroken and that the timing of the activities of the corpus allatum is controlled by the brain. The normal regulation of the corpus allatum is dependent on its connexion with the central nervous system, and the signal to the corpus allatum to change its secretory activity comes from the brain. Insect endocrinology provides some of the paradigms that are used in studies on the regulation of juvenile hormone biosynthesis by the corpus allatum. The chapter presents some of the evidence for the regulation of the corpus allatum activity and the mechanism of regulation. It also discusses some of the future experimental directions that can provide unequivocal data on the regulatory mechanisms of insect endocrine systems.

Regulation of the corpora allata in adult female insects

Effect of precocene II on the endocrine regulation of development and reproduction in the bug, Oncopeltus fasciatus.

Corpora allata fromOncopeltus fasciatus incubated in vitro in medium containing 10−5.35 M (1 μg/ml) of precocene II lose their ability to secrete juvenile hormone when reimplanted into last instar larvae.

P. Masner

Papers

Effect of precocene II on the endocrine regulation of development and reproduction in the bug, Oncopeltus fasciatus.

In vitro inactivation of corpora allata of the bugOncopeltus fasciatus by precocene II