E93 is indispensable for reproduction in ametabolous and hemimetabolous insects.

Ecdysone-induced protein 93 (E93), known as the "adult-specifier" transcription factor in insects, triggers metamorphosis in both hemimetabolous and holometabolous insects. While E93 is conserved in ametabolous insects, its spatiotemporal expression and physiological function remain poorly understood. In this study, we first discovered that in the ametabolous firebrat Thermobia domestica, the previtellogenic ovary exhibits cyclically high E93 expression, and E93 mRNAs are broadly distributed in previtellogenic ovarioles. E93 homozygous mutant females of T. domestica exhibit severe fecundity deficiency due to impaired previtellogenic development of the ovarian follicles, likely because E93 induces the expression of genes involved in ECM (extracellular matrix)-receptor interactions during previtellogenesis. Moreover, we revealed that in the hemimetabolous cockroach Blattella germanica, E93 similarly promotes previtellogenic ovarian development. In addition, E93 is also essential for vitellogenesis to guarantee ovarian maturation and promotes the vitellogenesis-previtellogenesis switch in the fat body of adult female cockroaches. Our findings deepen the understanding of the roles of E93 in controlling reproduction in insects and of E93 expression and functional evolution, which are proposed to have made crucial contributions to the origin of insect metamorphosis.

Molecular docking and molecular dynamics simulation study on the toxicity mechanism of bongkrekic acid.

BKA belongs to gram-negative brevibacterium. It can cause poisoning in humans or animals and can be fatal in severe cases. There are few investigations on toxic mechanisms of BKA because of foodborne factors. MD simulations were used to study the stability and intermolecular interactions of BKA and ANT complexes to reveal the mechanism of BKA in this paper. BKA blocked ANT protein translocation mainly through Van der Waals force, hydrophobic and hydrogen bonding interactions by the MD simulations. The conformational flexibility of the complex system during different simulation times indicated that BKA affected the conformational changes of ANT through strong interactions of hydrogen bonds with active domain residues Gln-93, Tyr-196, Arg-287 and Arg-245. The results of binding free energy, principal component analysis, hydrophobic interactions and root-mean-square fluctuation showed that the prominent binding force of Tyr-196 with C26 of BKA was significant to the toxicity. The active site interactions analysis indicated that the essential positively charged polar amino acids which play a crucial role within the active site of the ANT protein undergo conformational changes with BKA as the branch point.

Life-History Traits from Embryonic Development to Reproduction in the American Cockroach.

The American cockroach, Periplaneta americana (Insecta: Blattodea: Solumblattodea: Blattidae), is an urban hygiene pest but also a model organism for physiology and neuroscience study. However, the current description of the developmental process of the American cockroach is insufficient. In this study, we provide a life table of the American cockroach in a stable environment, including embryonic development, nymphal instars and adult reproduction. Our results show that there are 14 nymphal instars of the American cockroach in groups with sufficient living materials and space. The secondary sexual characteristics are evident in last-instar nymphs and adults, namely, the complete absence of the anal stylus in females. The entire embryonic development process was divided into 20 stages on the basis of lateral-view observations of the embryos. The formation of the embryo involves the fusion of paired blastoderm regions with higher cellular density, similar to that in other insects of Polyneoptera. With respect to reproduction, the gamogenetic females produced their first ootheca earlier than the parthenogenic females, and the frequency of oviposition was higher for the former throughout adulthood. Interestingly, group living seems to improve the parthenogenesis success rate in the American cockroach.