Insecticidal crystal proteins of Bacillus thuringiensis.

characterized by its ability to produce crystalline inclusions during spor-ulation. TIhese inclusions consist of proteins exhibiting a highly specific insecticidal activity (reviewed in references 4 and 97). Many B. thuriuigiensis strains with different insect host spectra have been identified (9). TIhey ar-e classified into different serotypes or subspecies based on their flagellar antigens. Most strains are active against larvae of certain members of the Lepidoptera, but some show toxicity against dipterian (reviewed in refer-ence 22) or coleopteran (53) species. For several cryst.al-producing strains.

Insecticidal crystal proteins of Bacilllus thuringiensis

Proanthocyanidins are oligomeric and polymeric end products of the flavonoid biosynthetic pathway. They are present in the fruits, bark, leaves and seeds of many plants, where they provide protection against predation. At the same time they give flavor and astringency to beverages such as wine, fruit juices and teas, and are increasingly recognized as having beneficial effects on human health. The presence of proanthocyanidins is also a major quality factor for forage crops. The past 2 years have seen important breakthroughs in our understanding of the biosynthesis of the building blocks of proanthocyanidins, the flavan-3-ols (+)-catechin and (-)-epicatechin. However, virtually nothing is known about the ways in which these units are assembled into the corresponding oligomers in vivo. Molecular genetic approaches are leading to an understanding of the regulatory genes that control proanthocyanidin biosynthesis, and this information, together with increased knowledge of the enzymes specific for the pathway, will facilitate the genetic engineering of plants for introduction of value-added nutraceutical and forage quality traits.

/pdf/proanthocyanidins-a-final-frontier-in-flavonoid-research-2d9bo57ypm.pdf

Proanthocyanidins--a final frontier in flavonoid research?

Insecticides derived from the common soil bacterium Bacillus thuringiensis (Bt) are becoming increasingly important for pest management. Insecticidal crystal proteins (also called 8-endotoxins) from Bt are extremely toxic to certain pests, yet cause little or no hann to humans, most beneficial insects, and other nontarget organisms (19, 40). After proteolytic activation in the insect midgut, Bt toxins bind to the brush border membrane of the midgut epithelium and create pores that cause cells to swell and lyse (55). Technical innovations, including expression of Bt toxin genes in transgenic crop plants and transgenic bacteria, should increase the usefulness of Bt (6, 12, 35, 46, 91, 94, 109, 116). At the same time, mounting concerns about environmental hazards and widespread resistance in pest populations are reducing the value of conventional synthetic insecticides. Because Bt had been used commercially for more than two decades without reports of substantial resistance development in open field popu­ lations, some scientists had presumed that evolution of resistance was unlikely (21, 89). However, resistance to Bt was documented recently in field populations of diamondback moth in Hawaii, the continental US, and Asia (36, 42, 92a, 128, 129, 131, 138, 146, 148, 151). These reports confirmed suspicions raised by the results of laboratory selection for resistance to Bt in several major pests (102, 104, 135). Scientists in industry, government, and academia now recognize evolution of resistance to Bt in pests as the greatest threat to the continued success of Bt (18, 44, 58, 59, lOla, 108). To delay or reverse resistance to Bt in pests, we must first understand

Evolution of Resistance to Bacillus Thuringiensis

Bacillus thuringiensis (Bt) is a soil bacterium that forms spores during the stationary phase of its growth cycle. The spores contain crystals, predominantly comprising one or more Cry and/or Cyt proteins (also known as δ-endotoxins) that have potent and specific insecticidal activity. Different strains of Bt produce different types of toxin, each of which affects a narrow taxonomic group of insects. Therefore, Bt toxins have been used as topical pesticides to protect crops, and more recently the proteins have been expressed in transgenic plants to confer inherent pest resistance. Bt transgenic crops have been overwhelmingly successful and beneficial, leading to higher yields and reducing the use of chemical pesticides and fossil fuels. However, their deployment has attracted some criticism particularly with regard to the potential evolution of pest-resistant insect strains. Here, we review recent progress in the development of Bt technology and the countermeasures that have been introduced to prevent the evolution of resistant insect populations.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1467-7652.2011.00595.x

Bacillus thuringiensis: a century of research, development and commercial applications.

A process for altering the insect host range (spectrum) of pesticidal toxins comprises recombining in vitro the variable region(s) (non-homologous) of two or more genes encoding a pesticidal toxin Specifically exemplified is the recombining of the variable regions of two genes obtained from well-known strains of Bacillus thurinaiensis var kurstaki The resulting products are chimeric toxins which are shown to have an expanded and/or amplified insect host range as compared to the parent toxins

Bacillus thuringiensis toxins

An isolate of Bacillus thuringiensis has been identified with toxic activity against coleopteran insects but not against lepidopteran or dipteran species. Toxin crystals from this strain contain a polypeptide of approximately 64,000 molecular weight possessing insecticidal activity. This toxin differs in polypeptide composition from other reported Bacillus thuringiensis toxins and does not appear to be processed from a larger precursor form. Insecticidal activity against the Colorado potato beetle and the boll weevil suggests the possibility of commercial applications of this strain.

A New Strain of Bacillus thuringiensis with Activity Against Coleopteran Insects

The invention concerns novel isolates of Bacillus thuringiensis (B.t.) which contains a toxin(s) which is active against adult nematode worms and larvae. This B.t. toxin(s) can be used to treat animals and plants hosting susceptible nematodes.

Novel isolates of bacillus thuringiensis having activity against nematodes

Novel biological pesticides are prepared by introducing into a microorganism the genetic capability to produce a heterologous pesticide, wherein the microorganism is capable of proliferating in the rhizosphere or phylloplane in competition with wild-type microorganisms. A gene capable of expressing a polypeptide is introduced into the microorganism under conditions which allow for stable maintenance and expression of the gene, without significantly diminishing the ability of the microorganism to compete in the environment. Preferred microorganisms provide for the maintenance and protection from degradation of the polypeptide pesticide.

Pseudomas hosts transformed with bacillus endotoxin genes

Biological pesticides are prepared by 
introducing into a microorganism the genetic capability 
to produce a heterologous pesticide, wherein the micro­
organism is capable of proliferating in the rhizosphere 
or phylloplane in competition with wild-type microor­
ganisms. A gene capable of expressing a polypeptide is 
introduced into the microorganism under conditions which 
allow for stable maintenance and expression of the gene, 
without significantly diminishing the ability of the 
microorganism to compete in the environment. Preferred 
microorganism provide for the maintenance and protection 
from degradation of the polypeptide pesticide.

David L. Edwards

Papers

Bacillus thuringiensis toxins

A New Strain of Bacillus thuringiensis with Activity Against Coleopteran Insects

Novel isolates of bacillus thuringiensis having activity against nematodes

Pseudomas hosts transformed with bacillus endotoxin genes

Microorganisms as pesticides