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Modification of the coding sequence enhances plant expression of insect control protein genes.

Increased expression of the insect control protein genes of Bacillus thuringiensis in plants has been critical to the development of genetically improved plants with agronomically acceptable levels of insect resistance. The expression of the cryIA(b) gene was compared to partially modified (3% nucleotide difference) and to fully modified (21% nucleotide difference) cryIA(b) and cryIA(c) genes in tobacco and tomato. The modified genes increased the frequency of plants that produced the proteins at quantities sufficient to control insects and dramatically increased the levels of these proteins. Among the most highly expressing transformed plants for each gene, the plants with the partially modified cryIA(b) gene had a 10-fold higher level of insect control protein and plants with the fully modified cryIA(b) had a 100-fold higher level of CryIA(b) protein compared with the wild-type gene. Similar results were obtained with the fully modified cryIA(c) gene in plants. Specific sequences of the partially modified cryIA(b) gene were analyzed for their ability to affect cryIA(b) gene expression in tobacco. The DNA sequence of a single region was identified as important to the improvement of plant expression of the cryIA(b) gene. The increased levels of cryIA(b) mRNA were not directly proportional to the increased levels of CryIA(b) protein in plants transformed with the modified cryIA(b) genes, indicating that the nucleotide sequence of these genes had an effect in improving their translational efficiency in plants.

Bacillus thuringiensis

Development of morphogenetic agents in insect control.

Chemicals which interfere with the growth and development of insects (morphogenetic agents) have been receiving major attention as potential means of selective insect control. Major advances in this field resulted from the identification of Juvenile Hormones -1, -2, and -3, and the discovery that various terpenoid and sesquiterpenoid derivatives were more potent morphogenetic agents than the three known Juvenile Hormones. Several highly active compounds have emerged from these research programs. Their field performance, problems, and prospects in selective insect control are considered here.

Animals

Insect growth regulators and insect control: a critical appraisal.

Insect growth regulators (IGRs) of the juvenile hormone type alter physiological processes essential to insect development and appear to act specifically on insects. Three natural juvenile hormones have been found in insects but not in other organisms. Future use of antagonists or inhibitors of hormone synthesis may be technically possible as an advantageous extension of pest control by IGRs. A documented survey of the properties, metabolism, toxicology, and uses of the most commercially advanced chemical, methoprene, shows it to be environmentally acceptable and toxicologically innocuous. Derivation of its current use patterns is discussed and limitations on these are noted. Residue levels and their measurement in the ppb region have allowed exemption from the requirement of tolerances in the EPA registered use of methoprene for mosquito control. Tolerances for foods accompany its fully approved use for control of manure breeding flies through a cattle feed supplement. The human health effects of using this chemical appear to be purely beneficial, but further advances through new IGR chemicals appear unlikely without major changes in regulatory and legislative policy.

Animals

Approaches to insect control based on chemical ecology--case studies.

In this article two attempted approaches to control a stored product insect, azuki bean weevil, are discussed based on host selection study and oviposition ecology. The latter study indicated the presence of an oviposition marker, a new kind of pheromone, which was derived from the weevil and was lipid in nature, and suggested its possible use as an oviposition inhibitor.

Animals

Public health advantages of biological insect controls.

Biological control is not new, it is simply newly appreciated. This renewed appreciation stems from the widespread insecticide treadmill which is largely a product of insecticide disruption of the balance of insect communities. Biological control is a natural phenomenon; the regulation of plant and animal numbers by natural enemies. In this broad sense, biological control is vital to public health because it keeps the myriad insect species from out-competing us. It also has direct public health advantages as where natural enemies are manipulated to control disease vectoring insects. Insecticide distruption of biological control by insecticides and the resulting pesticide treadmill have serious public health implications. One is the increased pesticide load in the environment. The other is the acceleration of pesticide resistance in disease vectoring insects. The treadmill and its associated hazards will not abate so long as chemical control dominates our pest management strategy.

Environmental Health

V-ATPase-energized epithelia and biological insect control.

Background is provided for the experimentally detailed contributions concerning the structure, distribution and function of V-ATPase-based ion pumps in insect epithelia. The mode of action of an insecticidal bacterial protein, which is dependent upon the V-ATPase-energized state in larval lepidopteran midgut for activity, is discussed.

Adenosine Triphosphatases

Effect of insect control on the occurrence and distribution of streptothricosis lesions on cattle.

Trials were set up to ascertain whether the observed occurrence of streptothricosis lesions at dorsal sites on cattle in Antigua was related to the feeding activity of flies. Animals in two herds were treated with insecticide while a third herd served as an untreated control group. There was no significant difference in the occurrence or distribution of lesions on animals in all the three herds over a two month observation period except that a higher proportion of animals in one of the treated herds was affected at the end of the study.

Actinomycetales Infections

Yorkie/Scalloped-OVOL-Rac1 axis controls insect wing development by promoting cell proliferation.

The regulation of organ size is a fundamental question in developmental biology, and insect wings provide a powerful model for elucidating the genetic mechanisms underlying morphogenesis. Although the conserved Hippo signaling pathway plays a central role in controlling tissue growth, its precise regulatory network during wing development remains incompletely understood. Here, we identify the zinc finger transcription factor OVOL as a critical mediator of Hippo signaling in insect wing development. We indicate that OVOL is essential for normal wing formation in both Locusta migratoria and Drosophila melanogaster, regulating cell proliferation and trichome patterning. Through transcriptomic analysis and functional validation, we further identify the small GTPase Rac1 as a key downstream effector of OVOL that promotes proliferative growth. Moreover, we find that OVOL expression is directly activated by the Yorkie/Scalloped (Yki/Sd) complex, the core transcriptional effector of the Hippo pathway, without forming a feedback loop. This regulation is mediated through a specific Sd-binding motif (GATAA) within the OVOL promoter. Importantly, Yki/Sd-induced Rac1 expression is dependent on OVOL. Collectively, our findings establish the Yorkie/Sd-OVOL-Rac1 pathway that governs insect wing development by promoting cell proliferation, providing mechanistic insights into organ size regulation in animals.

Cell proliferation

Insect-control chemicals from plants. III. Toxic lignans from Libocedrus bidwillii.

Feeding tests showed that the powdered dried leaves and leaf extracts of L. bidwilli are toxic to the larvae of the housefly (Musca domestica), and the codling moth (Laspeyresia pomonella). The powdered material was not toxic to the light-brown apple moth (Epiphyas postvittana). The most active toxin is the lignan beta-peltatin-A methyl ether (II) and at a concentration of 100 ppm in a chemically defined diet it gave 98% mortality of housefly larvae.

Animals