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Regulation of the packaging of Bacillus thuringiensis delta-endotoxins into inclusions.
Appl Environ Microbiol. 2001 Nov; 67(11):5032-6.AE

Abstract

During sporulation, many Bacillus thuringiensis subspecies synthesize several related delta-endotoxins which are packaged into bipyramidal intracellular inclusions. These inclusions are solubilized in the alkaline, reducing conditions of the midguts of susceptible insect larvae and are converted by proteolysis to active toxins. The toxins insert into the membranes of cells lining the midgut and form cation-selective channels, which results in lethality. There are three delta-endotoxins, Cry1Ab3, Cry1Ca1, and Cry1Da1, present in the inclusions produced by a B. thuringiensis subsp. aizawai cell. While the ratio of the steady-state mRNAs for these three protoxins has been shown to differ (cry1Ab3/cry1Ca1/cry1Da1 mRNA ratio, 4:2:1), the half-lives of the cry1Da1 and cry1Ab3 mRNAs were found to be similar, indicating that there were differences in the transcription rates. The relative contents of these delta-endotoxins in purified inclusions from B. thuringiensis subsp. aizawai have been measured previously, and an even greater relative deficiency of the Cry1Da1 protoxin (ratio, 20:12:1) was found. In order to account for this deficiency, other steps which could be involved in inclusion formation, such as translation and packaging, were examined. The three cry genes have the same dual overlapping promoters, but the ribosome binding sequence for the cry1Da1 gene was not the consensus sequence. Translation was enhanced about fourfold by changing to the consensus sequence. In addition, the relative amount of Cry1Da1 protoxin in inclusions was twofold lower when cells were sporulated in Luria-Bertani (LB) medium than when cells were sporulated in a glucose-yeast extract medium. This difference was attributable to packaging since the relative amounts of Cry1Da1 antigen in cells sporulating in the two media were the same. Some factor(s) required for packaging of the Cry1Da1 protoxin in inclusions is apparently limiting in LB medium. Differences in the initial transcription rates, translation efficiencies, and packaging all contribute to the delta-endotoxin composition of an inclusion.

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Authors+Show Affiliations

Chang L
Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA.
Grant R
No affiliation info available
Aronson A
No affiliation info available

MeSH

Amino Acid SequenceBacillus thuringiensisBacillus thuringiensis ToxinsBacterial ProteinsBacterial ToxinsEndotoxinsGene Expression Regulation, BacterialHemolysin ProteinsInclusion BodiesMolecular Sequence DataProtein BiosynthesisProtein PrecursorsRNA StabilityRNA, BacterialRNA, MessengerSpores, BacterialTranscription, Genetic

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

11679322

Citation

Chang, L, et al. "Regulation of the Packaging of Bacillus Thuringiensis Delta-endotoxins Into Inclusions." Applied and Environmental Microbiology, vol. 67, no. 11, 2001, pp. 5032-6.
Chang L, Grant R, Aronson A. Regulation of the packaging of Bacillus thuringiensis delta-endotoxins into inclusions. Appl Environ Microbiol. 2001;67(11):5032-6.
Chang, L., Grant, R., & Aronson, A. (2001). Regulation of the packaging of Bacillus thuringiensis delta-endotoxins into inclusions. Applied and Environmental Microbiology, 67(11), 5032-6.
Chang L, Grant R, Aronson A. Regulation of the Packaging of Bacillus Thuringiensis Delta-endotoxins Into Inclusions. Appl Environ Microbiol. 2001;67(11):5032-6. PubMed PMID: 11679322.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Regulation of the packaging of Bacillus thuringiensis delta-endotoxins into inclusions. AU - Chang,L, AU - Grant,R, AU - Aronson,A, PY - 2001/10/27/pubmed PY - 2002/1/18/medline PY - 2001/10/27/entrez SP - 5032 EP - 6 JF - Applied and environmental microbiology JO - Appl Environ Microbiol VL - 67 IS - 11 N2 - During sporulation, many Bacillus thuringiensis subspecies synthesize several related delta-endotoxins which are packaged into bipyramidal intracellular inclusions. These inclusions are solubilized in the alkaline, reducing conditions of the midguts of susceptible insect larvae and are converted by proteolysis to active toxins. The toxins insert into the membranes of cells lining the midgut and form cation-selective channels, which results in lethality. There are three delta-endotoxins, Cry1Ab3, Cry1Ca1, and Cry1Da1, present in the inclusions produced by a B. thuringiensis subsp. aizawai cell. While the ratio of the steady-state mRNAs for these three protoxins has been shown to differ (cry1Ab3/cry1Ca1/cry1Da1 mRNA ratio, 4:2:1), the half-lives of the cry1Da1 and cry1Ab3 mRNAs were found to be similar, indicating that there were differences in the transcription rates. The relative contents of these delta-endotoxins in purified inclusions from B. thuringiensis subsp. aizawai have been measured previously, and an even greater relative deficiency of the Cry1Da1 protoxin (ratio, 20:12:1) was found. In order to account for this deficiency, other steps which could be involved in inclusion formation, such as translation and packaging, were examined. The three cry genes have the same dual overlapping promoters, but the ribosome binding sequence for the cry1Da1 gene was not the consensus sequence. Translation was enhanced about fourfold by changing to the consensus sequence. In addition, the relative amount of Cry1Da1 protoxin in inclusions was twofold lower when cells were sporulated in Luria-Bertani (LB) medium than when cells were sporulated in a glucose-yeast extract medium. This difference was attributable to packaging since the relative amounts of Cry1Da1 antigen in cells sporulating in the two media were the same. Some factor(s) required for packaging of the Cry1Da1 protoxin in inclusions is apparently limiting in LB medium. Differences in the initial transcription rates, translation efficiencies, and packaging all contribute to the delta-endotoxin composition of an inclusion. SN - 0099-2240 UR - https://www.unboundmedicine.com/medline/citation/11679322/Regulation_of_the_packaging_of_Bacillus_thuringiensis_delta_endotoxins_into_inclusions_ L2 - https://journals.asm.org/doi/10.1128/AEM.67.11.5032-5036.2001?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -