Embryonic terminal patterning and moulting are critical developmental processes in insects. In Drosophila and Tribolium both of these processes are regulated by the Torso‐activation cassette (TAC). The TAC consists of a common receptor, Torso, ligands Trunk and prothoracicotropic hormone (PTTH), and the spatially restricted protein Torso‐like, with combinations of these elements acting mechanistically to activate the receptor in different developmental contexts. In order to trace the evolutionary history of the TAC we determined the presence or absence of TAC components in the genomes of arthropods. Our analyses reveal that Torso, Trunk and PTTH are evolutionarily labile components of the TAC with multiple individual or combined losses occurring in the arthropod lineages leading to and within the insects. These losses are often correlated, with both ligands and receptor missing from the genome of the same species. We determine that the PTTH gene evolved in the common ancestor of Hemiptera and Holometabola, and is missing from the genomes of a number of species with experimentally demonstrated PTTH activity, implying another molecule may be involved in ecdysis in these species. In contrast, the torso‐like gene is a common component of pancrustacean genomes.

Enveloped viruses hijack cellular membranes in order to provide the necessary material for virion assembly. In particular, viruses that replicate and assemble inside the nucleus have developed special approaches to modify the nuclear landscape for their advantage. We used electron microscopy to investigate cellular changes occurring during nudivirus infection and we characterized a unique mechanism for assembly, packaging, and transport of new virions across the nuclear membrane and through the cytoplasm. Our three-dimensional reconstructions describe the complex remodeling of the nuclear membrane necessary to release vesicle-associated viruses into the cytoplasm. This is the first report of nuclear morphological reconfigurations that occur during nudiviral infection. IMPORTANCE The dynamics of nuclear envelope has a critical role in multiple cellular processes. However, little is known regarding the structural changes occurring inside the nucleus or at the inner and outer nuclear membranes. For viruses assembling inside the nucleus, remodeling of the intranuclear membrane plays an important role in the process of virion assembly. Here, we monitored the changes associated with viral infection in the case of nudiviruses. Our data revealed dramatic membrane remodeling inside the nuclear compartment during infection with Oryctes rhinoceros nudivirus, an important biocontrol agent against coconut rhinoceros beetle, a devastating pest for coconut and oil palm trees. Based on these findings, we propose a model for nudivirus assembly in which nuclear packaging occurs in fully enveloped virions.

The DSIR-HA-1179 coleopteran cell line is a susceptible and permissive host to the Oryctes rhinoceros nudivirus (OrNV), which has been used as a biocontrol agent against the coconut rhinoceros beetle (Oryctes rhinoceros); a pest of palms in the Asia-Pacific region. However, little is known about growth and metabolism of this cell line, knowledge of which is necessary to develop an in vitro large-scale OrNV production process. The strong anchoragedependent characteristics of the cell line, its particular fragility and its tendency to form dense clumps when manipulated, are the most likely reasons that have precluded further development of the cell line. In order to characterize DSIR-HA-1179 cells, there was first a need for a reliable technique to count the cells. A homogenous cell suspension suitable for enumeration could be produced by treatment with TrypLE Express TM with optimum mean time for cell release calculated as 30 min. The cell line was adapted to grow in four serum-supplemented culture media namely TC-100, IPL-41, Sf-900 II and Sf-900 III and cell growth, glucose consumption, lactate and ammonia production were assessed from static-batch cultures. The maximum viable cell density was reached in Sf-900 II (17.9 9 10 5 cells/ml), with the maximum specific growth rate observed in this culture medium as well (0.0074 h -1 ). Higher production of OrNV was observed in IPL-41 and TC-100 (4.1 9 10 7 TCID 50 /ml) than in cultures infected in Sf-900 III (2.0 9 10 7 TCID 50 /ml) and Sf-900 II (1.4 9 10 7 TCID 50 /ml). At the end of the growth period, glucose was completely consumed in cultures grown in TC-100, while remained in excess in the other three culture media. The cell line produced lactate and ammonia to very low levels in the TC-100 culture medium which is a promising aspect for its cultivation at large-scale.

While large-scale culture of insect cells will need to be conducted using bioreactors up to 10,000 l scale, many of the main challenges for cell culture-based production of insecticidal viruses can be studied using small-scale (20-500 ml) shaker/spinner flasks, either in free suspension or using microcarrier-based systems. These challenges still relate to the development of appropriate cell lines, stability of virus strains in culture, enhancing virus yields per cell, and the development of serum-free media and feeds for the desired production systems. Hence this chapter presents mainly the methods required to work with and analyze effectively insect cell systems using small-scale cultures. Outlined are procedures for quantifying cells and virus and for establishing frozen cells and virus stocks. The approach for maintaining cell cultures and the multiplicity of infection (MOI) and time of infection (TOI) parameters that should be considered for conducting infections are discussed.The methods described relate, in particular, to the suspension culture of Helicoverpa zea and Spodoptera frugiperda cell lines to produce the baculoviruses Helicoverpa armigera nucleopolyhedrovirus, HearNPV, and Anticarsia gemmatalis multicapsid nucleopolyhedrovirus, AgMNPV, respectively, and the production of the nonoccluded Oryctes nudivirus, OrNV, using an adherent coleopteran cell line.

The DSIR-HA-1179 coleopteran cell line has been identified as a susceptible and permissive host for the in vitro replication of the Oryctes nudivirus, which can be used as a biopesticide against the coconut rhinoceros beetle, pest of palms. The major challenge to in vitro large-scale Oryctes nudivirus production is ensuring process economy. This rests, among other requisites, on the use of low-cost culture media tailored to the nutritional and metabolic needs of the cell line, both in uninfected and infected cultures. The aim of the present study was to characterize the nutritional demands and the metabolic characteristics of the DSIR-HA-1179 cell line during growth and subsequent infection with Oryctes nudivirus in the TC-100 culture medium. Serum-supplementation of the culture medium was found to be critical for cell growth, and addition of 10% fetal bovine serum v/v led to a maximum viable cell density (16.8 × 10 cells ml) with a population doubling time of 4.2 d. Nutritional and metabolic characterization of the cell line revealed a trend of glucose and glutamine consumption but minimal uptake of other amino acids, negligible production of lactate and ammonia, and the accumulation of alanine, both before and after infection. The monitoring of virus production kinetics showed that the TC-100 culture medium was nutritionally sufficient to give a peak yield of 7.38 × 10 TCID ml of OrNV at the 6th day post-infection in attached cultures of DSIR-HA-1179 cells in 25 cm T-flasks. Knowledge of the cell line's nutritional demands and virus production kinetics will aid in the formulation of a low-cost culture medium and better process design for large-scale OrNV production in future.