Specific activity of a Bacillus thuringiensis strain against Locusta migratoria manilensis

Bacillus thuringiensis (Bt) has played an important role in biocontrol of pests. However, insecticidal activity of B. thuringiensis against locusts has been rarely reported. Bt strain BTH-13 exhibiting specific activity to locusts was isolated from a soil sample in China and characterized. Its bipyramidal parasporal crystal is mainly composed of a protein of 129 kDa, and produces a mature toxin of 64 kDa after activation. The pattern of total DNA from BTH-13 showed a large and three small plasmid bands. Known δ-endotoxin genes, cry1Aa, cry1Ab, cry1Ac, cry1C, cry3, cry4 and cry7Aa were not found from strain BTH-13 by PCR amplification. The sequence analysis of a DNA fragment produced by PCR amplification with degenerate cry-selective primers revealed that the fragment encoded a δ-endotoxin segment, which exhibited some similarity to several Cry proteins (41% of the highest similarity to Cry7Ba1). Toxicity tests were performed against Locusta migratoria manilensis, and the results demonstrated that trypsin-treated sporulated cultures and crystal proteins had high toxicity to larval and adult locusts. Cry toxin of BTH-13 was detected on the midguts of treated locusts using immunofluorescent technology, which confirmed the site of action of the crystal proteins in their toxicity for locusts.     

Molecular cloning and characterization of a novel mosquitocidal protein gene from Bacillus thuringiensis subsp. fukuokaensis.

A novel mosquitocidal protein gene, cry20Aa, was cloned from Bacillus thuringiensis subsp. fukuokaensis (H-3a: 3d: 3e). The gene product, Cry20Aa, was naturally truncated and had a molecular mass of 86,138 Da. The Cry20Aa protein possessed five conserved sequence blocks, as do most other insecticidal Cry toxins. However, an amino acid comparison of Cry20Aa with other mosquitocidal toxins, including Cry4A, Cry4B, Cry10A, Cry11A, and Cry11B, demonstrated that Cry20Aa was quite different from other toxins except for the conserved blocks. The N terminus of Cry20Aa was, however, homologous to the N termini of Cry4A and Cry10A. Interestingly, an inverted repeat (IR1) sequence in the open reading frame of the cry20Aa gene caused incomplete expression of Cry20Aa. When this internal IR1 sequence was altered with no change of amino acid sequence, acrystalliferous B. thuringiensis cells transformed with cry20Aa gene dramatically produced crystal inclusions. However, the intact 86-kDa Cry20Aa protein is highly labile, and it is rapidly degraded to polypeptides of 56 and 43 kDa. To increase expression of the cry20Aa gene, the p20 chaperonelike protein and the cyt1Aa promoter were utilized. While p20 did not increase Cry20Aa expression or stability, chimeric constructs in which the cry20Aa gene was under control of the cyt1Aa promoter overexpressed the Cry20Aa protein in acrystalliferous B. thuringiensis. The expressed Cry20Aa protein showed larvicidal activity against Aedes aegypti and Culex quinquefasciatus. However, the mosquitocidal activity was low, probably due to rapid proteolysis to inactive 56- and 43-kDa proteins.     

苏云金芽胞杆菌高效表达载体的构建

[目的]通过比较cry1A、cry3A、cry4A和cry8E四个基因的启动子转录活性,筛选出一个强启动子,利用强启动子构建一个苏云金芽胞杆菌(Bacillus thuringiensis,简称Bt)高效表达载体.[方法]利用启动子融合lacZ技术检测了4种启动子的转录活性.通过扫描电子显微镜观察晶体、SDS-PAGE、蛋白定量和生物活性测定等方法对新建高效表达载体进行功能验证.[结果]构建了Pcry1A、Pcry3A、Pcry4A和Pcry8E4个启动子融合报告基因lacZ的表达载体,经β-半乳糖苷酶活性分析得知,启动子活性从高到低依次为Pcry8E＞Pcry1A＞Pcry4A＞Pcry3A.选取cry8E启动子,以pHT315作为基础载体构建苏云金芽胞杆菌高效表达载体pHT315-8E21b,将cry1Ac基因连接到pHT315-8E21b和广泛应用的cry3A启动子指导的pSXY-422b上,分别转入无晶体突变株HD-73-,获得菌株HD-8E1Ac和HD-422-1Ac.扫描电子显微镜观察显示,HD-8E1Ac菌株可以形成菱形晶体,说明正确表达了cry1Ac基因.SDS-PAGE分析结合蛋白定量实验表明pHT315-8E21b表达效率高于pSXY-422b.对小菜蛾(Plutella xylostella)的生物活性测定表明HD-8E1Ac菌株对小菜蛾有生物活性,且菌株活性高于HD-422-1Ac.[结论]利用强启动子Pcry8E构建了一个能在Bt中高效表达的穿梭载体pHT315-8E21b,该载体可正确表达cry1Ac基因,其表达效率高于被广泛应用的pSXY422b.     

The 60-kilodalton protein encoded by orf2 in the cry19A operon of Bacillus thuringiensis subsp. jegathesan functions like a C-terminal crystallization domain

The cry19A operon of Bacillus thuringiensis subsp. jegathesan encodes two proteins, mosquitocidal Cry19A (ORF1; 75 kDa) and an ORF2 (60 kDa) of unknown function. Expression of the cry19A operon in an acrystalliferous strain of B. thuringiensis (4Q7) yielded one small crystal per cell, whereas no crystals were produced when cry19A or orf2 was expressed alone. To determine the function of the ORF2 protein, different combinations of Cry19A, ORF2, and the N- or C-terminal half of Cry1C were synthesized in strain 4Q7. Stable crystalline inclusions of these fusion proteins similar in shape to those in the strain harboring the wild-type operon were observed in sporulating cells. Comparative analysis showed that ORF2 shares considerable amino acid sequence identity with the C-terminal region of large Cry proteins. Together, these results suggest that ORF2 assists in synthesis and crystallization of Cry19A by functioning like the C-terminal domain characteristic of Cry protein in the 130-kDa mass range. In addition, to determine whether overexpression of the cry19A operon stabilized its shape and increased Cry19A yield, it was expressed under the control of the strong chimeric cyt1A-p/STAB-SD promoter. Interestingly, in contrast to the expression seen with the native promoter, overexpression of the operon yielded uniform bipyramidal crystals that were 4-fold larger on average than the wild-type crystal. In bioassays using the 4th instar larvae of Culex quinquefasciatus, the strain producing the larger Cry19A crystal showed moderate larvicidal activity that was 4-fold (95% lethal concentration [LC(95)] = 1.9 μg/ml) more toxic than the activity produced in the strain harboring the wild-type operon (LC(95) = 8.2 μg/ml).     

Differential enhancement of Cry2A versus Cry11A yields in Bacillus thuringiensis by use of the cry3A STAB mRNA sequence

Previously we demonstrated that the yield of Cry3A (70 kDa) can be increased as much as 10-fold when cry3A including its upstream STAB-SD mRNA stabilizing sequence is expressed in Bacillus thuringiensis under the control of cyt1A promoters. To determine whether the cyt1A promoters/STAB-SD combination (cyt1AP/STAB) has broader applicability, we used it to synthesize two other Cry endotoxins in the 70-kDa mass range, Cry2A and Cry11A. Combination of cyt1AP/STAB with orfs 2 and 3 of the cry2A operon yielded about 4. 4-fold the amount of Cry2A obtained with the wild-type cry2A operon. The yield of Cry11A obtained with a construct that contained the cyt1AP/STAB, cry11A and the 20-kDa protein gene was 1.3-fold the amount obtained with a construct similar to the wild-type operon. These results demonstrate that the cyt1AP/STAB combination can enhance synthesis of different Cry proteins significantly, but that the level of enhancement varies with the specific protein synthesized.     

Identification of a mosquitocidal toxin from Bacillus thuringiensis using mass spectrometry

The Bacillus thuringiensis strain S2160-1 has previously been identified as being highly toxic to mosquito larvae and a viable alternative to strains currently used commercially to control these insects. A PCR approach had identified the presence of four putative insecticidal toxin genes (cry30Ea, cry30 Ga, cry50Ba and cry54Ba) in this strain, but did not identify the genes that encoding three of the main crystal toxin proteins of size 140 and 130 and 30 kDa. In this study we used mass spectrometry to identify the 130 kDa toxin as a rare Cry4 toxin (Cry4Cb3). The gene encoding this toxin was cloned and expressed and the toxin shown to have mosquitocidal activity against Culex quinquefasciatus.     

A highly pathogenic strain of Bacillus thuringiensis serovar kurstaki in lepidopteran pests

In order to detect and identify the most toxic Bacillus thuringiensis strains against pests, we isolated a B. thuringiensis strain (Bn1) from Balaninus nucum (Coleoptera: Curculionidae), the most damaging hazelnut pest. Bn1 was characterized via morphological, biochemical, and molecular techniques. The isolate was serotyped, and the results showed that Bn1 was the B. thuringiensis serovar, kurstaki (H3abc). The scanning electron microscopy indicated that Bn1 has crystals with cubic and bipyramidal shapes. The Polymerase Chain Reactions (PCRs) revealed the presence of the cry1 and cry2 genes. The presence of Cry1 and Cry2 proteins in the Bn1 isolate was confirmed via SDS-PAGE, at approximately 130 kDa and 65 kDa, respectively. The bioassays conducted to determine the insecticidal activity of the Bn1 isolate were conducted with four distinct insects, using spore-crystal mixtures. We noted that Bn1 has higher toxicity as compared with the standard B. thuringiensis subsp. kurstaki (HD-1). The highest observed mortality was 90% against Malacosoma neustria and Lymantria dispar larvae. Our results show that the B. thuringiensis isolate (Bn1) may prove valuable as a significant microbial control agent against lepidopteran pests.     

Rapid cloning, identification, and application of one novel crystal protein gene cry30Fa1 from Bacillus thuringiensis

In this study, a fast and efficient strategy has been developed for identifying and isolating novel cry genes from Bacillus thuringiensis by combining the PCR-restriction fragment length polymorphism and the single-oligonucleotide nested-PCR method. Using this method, one novel holotype cry gene, cry30Fa1 , encoding a polypeptide of 687 amino acid residues with a molecular mass of 77.1 kDa, 74% identical to Cry30Aa1, was cloned from the B. thuringiensis strain BtMC28. Furthermore, the cry30Fa1 gene was successfully expressed in Escherichia coli BL21 (DE3). The Cry30Fa1 proteins, isolated from the cultures of recombinant E. coli , had remarkable insecticidal effects against Plutella xylostella and Aedes aegypti with LC50 at 6.477 and 15.359 μg mL⁻¹, respectively. Our results strongly suggest that this strategy is highly efficient and advantageous in terms of rapid cloning of holotype cry genes that have minimal identity to known genes. The cloning of the cry30Fa1 gene would be useful in the resources of the insecticidal crystal genes and may serve as an alternative choice of an insecticide for potential problems associated with insect resistance.     

苏云金芽胞杆菌Rpp39杀虫晶体蛋白基因的鉴定及cry2Aa12基因的克隆表达

[目的]本研究的目的是分析从四川生态条件下分离的苏云金芽胞杆菌Rpp39菌株的特性,从分子水平上揭示该菌株对鳞翅目高毒力的原因;进一步从中分离克隆cry2Aa基因,并对其进行初步的表达研究.[方法]本研究主要采用扫描电镜观察、PCR-RFLP鉴定法和SDS-PAGE分析法研究菌株的特性;采用PCR直接克隆法克隆cry2Aa全长基因,并亚克隆到原核表达载体pET-30a中,构建重组表达质粒pET-2Aa,再转入受体菌E.coli.BL21(DE3)中进行诱导表达;采用室内生物测定法测定表达产物对小菜蛾和水稻二化螟的毒力.[结果]经扫描电镜观察菌株Rpp39主要产生菱形、方形和圆形3种伴胞晶体;SDS-PAGE分析表明主要产生130 kDa和60 kDa左右2种蛋白;经PCR-RFLP鉴定,该菌株含有cry1Aa、cry1Ab、cry1Ac、cry1Ia和cry2Aa五类杀虫晶体蛋白基因;1种cry2Aa类杀虫晶体蛋白全长基因被克隆,序列分析显示该基因的开放阅读框(ORF)为1902 bps,编码由634个氨基酸组成的蛋白质,氨基酸序列与Cry2Aa1蛋白同源性为99.7%,被国际Bt杀虫晶体蛋白基因命名委员会命名为cry2Aa12.重组表达质粒pET-2Aa在E.coli BL21(DE3)中,经IPTG诱导能正常表达,SDS-PAGE电泳验证含有65 kDa表达蛋白.生物活性测定表明表达的包涵体蛋白对小菜蛾和二化螟具有杀虫活性,LC50分别为5.4 μg/mL和22.3μg/mL.[结论]菌株Rpp39及从中分离克隆的cry2Aa12基因来自四川生态条件,丰富了菌株及基因的资源,在资源积累方面具有重要意义.     

Towards novel Cry toxins with enhanced toxicity/broader: a new chimeric Cry4Ba / Cry1Ac toxin

Attempts have been made to express or to merge different Cry proteins in order to enhance toxic effects against various insects. Cry1A proteins of Bacillus thuringiensis form a typical bipyramidal parasporal crystal and their protoxins contain a highly conserved C-terminal region. A chimerical gene, called cry(4Ba-1Ac), formed by a fusion of the N-terminus part of cry4Ba and the C-terminus part of cry1Ac, was constructed. Its transformation to an acrystalliferous B. thuringiensis strain showed that it was expressed as a chimerical protein of 116 kDa, assembled in spherical to amorphous parasporal crystals. The chimerical gene cry(4Ba-1Ac) was introduced in a B. thuringiensis kurstaki strain. In the generated crystals of the recombinant strain, the presence of Cry(4Ba-1Ac) was evidenced by MALDI-TOF. The recombinant strain showed an important increase of the toxicity against Culex pipiens larvae (LC₅₀ = 0.84 mg l^?1 ± 0.08) compared to the wild type strain through the synergistic activity of Cry2Aa with Cry(4Ba-1Ac). The enhancement of toxicity of B. thuringiensis kurstaki expressing Cry(4Ba-1Ac) compared to that expressing the native toxin Cry4Ba, might be related to its a typical crystallization properties. The developed fusion protein could serve as a potent toxin against different pests of mosquitoes and major crop plants.     

Mode of action of Bacillus thuringiensis PS86Q3 strain in hymenopteran forest pests.

The mode of action of Cry toxins has been described principally in lepidopteran insects as a multistep process. In this work we describe the mode of action of a Cry toxin active in the common pine sawfly Diprion pini (Hymenoptera, Diprionidae), considered a major forest pest in Europe. Strain PS86Q3 contains a long bipyramidal crystal composed of five major proteins. The N-terminal sequence shows that the 155 kDa protein corresponds to Cry5B toxin and the other proteins belong to the Cry5A subgroup. PCR analysis indicates the presence of cry5Ac and cry5Ba genes, suggesting that Cry5A protein should be Cry5Ac. Activation of protoxins with trypsin or with midgut content from D. pini and Cephacia abietis (Hymenoptera, Pamphiliidae) (spruce webspinning sawfly), another important hymenopteran forest pest, produced a single 75 kDa toxin that corresponded to Cry5A by N-terminal sequence and is responsible for the insecticidal activity. Homologous competition experiments with D. pini and C. abietis brush border membrane vesicles (BBMV) showed that the binding interaction of Cry5A is specific. Membrane potential measurements using a fluorescent dye indicate that Cry5A toxin at nM concentration caused immediate permeability changes in the BBMV isolated from both hymenopteran larvae. The initial response and the sustained permeability change are cationic as previously shown for Cry1 toxins. These results indicate that the hymenopteran specific Cry5A toxin exerts toxicity by a similar mechanism as Cry1 toxins.     

Cloning and characterization of a novel gene cry9Ec1 encoding lepidopteran-specific parasporal inclusion protein from a Bacillus thuringiensis serovar galleriae strain

A novel delta-endotoxin gene from a lepidopteran-specific Bacillus thuringiensis serovar galleriae strain was cloned, and the full sequence of the cry gene was determined. The cloned 6.5-kb DNA fragment included the full sequence of the cry gene and three open reading frames located upstream of the cry gene. The gene, designated cry9Ec1, encodes a polypeptide of 1154 amino acid residues with a predicted molecular weight of 130 237. The deduced amino acid sequence of the Cry9Ec1 protein had the highest homology (77.7%) with the Cry9Ea1 protein when compared with existing Cry proteins. The expression, in an acrystalliferous B. thuringiensis strain, of the cry9Ec1 gene was high when controlled by the cyt1A2 promoter, leading to the formation of large spherical inclusions. The purified crystals from the recombinant strain were toxic when tested against two lepidopteran species, Bombyx mori and Plutella xylostella. However, the Cry9Ec1 protein gave no toxicity against Spodoptera litura, Spodoptera exigua, Plodia interpunctella, Helicoverpa zea, and Culex pipiens molestus.     

对粉纹夜蛾高毒力cry9Eα基因的克隆及表达

[目的]从本实验室分离的Bt4菌株中克隆cry9Eα基因,并研究其表达和杀虫活性.[方法]以PCR-RFLP方法鉴定Bt4菌株含有cry9基因,然后以菌株Bt4的质粒为模板,利用全长引物F9EA/R9EA进行PCR扩增全长基因.[结果]将目的片段插入到表达载体pET21b,得到大肠杆菌重组表达质粒pETcrygEa.转化E.coli BL21(DE3),诱导后表达130 kDa的蛋白,再将cry9Eα7基因连接到穿梭载体pSXY422b,电激转化HD73-(cry-),得到工程菌BioHD9Ea7,提取Cry9Ea7晶体蛋白,并进行生物活性测定.生物活性测定结果显示CrygEa7蛋白对粉纹夜蛾(Trichoplusia ni)初孵幼虫具有高毒力,LC_(50)为0.044 μg/mL,而对甜菜夜蛾(Spodoptera exigua)和棉铃虫(Helicoverpa armigera)初孵幼虫未显示活性.[结论]克隆和表达了一个对粉纹夜蛾高毒力的基因cry9Eα7,并成功构建了工程菌BioHD9Ea7.     

Novel cry gene from Paenibacillus lentimorbus strain Semadara inhibits ingestion and promotes insecticidal activity in Anomala cuprea larvae

A positive clone was selected from a library of total cell DNA of Paenibacillus lentimorbus strain Semadara that reacted with an antiserum that was raised against parasporal crystal proteins produced by this strain. The positive clone had a DNA insert containing two whole cry genes (cry43Aa1, cry43Ba1), one partial cry gene (cry43-like), and three smaller genes located upstream. Eight blocks that are conserved in the Cry proteins of Bacillus thuringiensis [Microbiol. Mol. Biol. Rev. 62 (1998) 775] were detected in their deduced amino acid sequences. The Escherichia coli transformant expressing cry43Aa1 caused inhibition of ingestion and 90% mortality in the first stadium larvae of Anomala cuprea. A low concentration of sporangia mixed with the transformant expressing cry43Aa1 easily infected the larvae of A. cuprea. The protein of approximately 150 kDa produced by the transformants expressing the cry genes reacted with antiserum specific for the parasporal crystal proteins. Southern hybridization analysis demonstrated that the cry genes were located on the chromosomal DNA of this strain, which possessed at least four cry genes.     

Detection and characterisation of a Bacillus thuringiensis crystal protein with nematicidal activity against the pinewood nematode Bursaphelenchus xylophilus

Nematicidal Bacillus thuringiensis (Bt) strains were isolated from forests in Zhejiang, China for further characterisation. PCR analysis was performed with nine pairs of primers specific for cry1, cry2, cry3, cry4, cry5, cry6, cry9, cry11 and cry13 to characterise and classify cry gene groups from Bt isolates. The isolates from individual cry groups were tested for nematicidal activity against the pinewood nematode Bursaphelenchus xylophilus, which is implicated in pine wilt disease. PCR identified 14 different categories of cry gene combinations, indicating a large diversity of cry genes. The cry1 gene was by far the most abundant in Bt isolates and was found in 68% of samples. The Bt isolates zjfc85 and zjfc392 were from two distinct classes, but shared the same cry5 amplification profile and the same ~130 kDa protein; they had the highest nematicidal activity against pinewood nematode during the 48 h exposure tests, resulting in 90 and 59% mortality (9% of mortality under control conditions), respectively. The ~130 kDa Cry protein from isolate zjfc85 was purified and named as Cry5Ba3. Bioassay results indicated pinewood nematode was highly susceptible to Cry5Ba3 and exhibited profound growth abnormalities after exposure to Cry5Ba3. Our results are a novel finding and provide a potential strategy to manage pine wilt disease caused by B. xylophilus based on a nematicidal Bt.     

Cloning and Characterization of Two Novel Crystal Protein Genes, <Emphasis Type="Italic">cry54Aa1</Emphasis> and <Emphasis Type="Italic">cry30Fa1</Emphasis>, from <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis> Strain BtMC28

Bacillus thuringiensis strain BtMC28 was isolated from the soil sample in China. Two novel crystal protein genes were found by using the PCR-RFLP method. Moreover, the full-length sequences of two novel genes were obtained by a single oligonucleotide nested (SON)-PCR upstream and downstream strategy. Sequence analysis revealed that one gene encoded a polypeptide of 673 amino acid residues with a molecular mass of 76.3 kDa, 38% identical to Cry10Aa, and the other encoded a polypeptide of 687 amino acid residues with a molecular mass of 77.1 kDa, 74% identical to Cry30Aa. These two novel crystal protein genes were designated as cry54Aa1 and cry30Fa1 by Bt Insecticidal Crystal Proteins Nomenclature Committee, respectively. The Cry54Aa1 and Cry30Fa1 proteins retained five conserved regions commonly found in the existing Cry proteins. Cry54Aa1 protein exhibited insecticidal activities against Laphygma exigua (Lepidoptera), Helicoverpa armigera (Lepidoptera), and Aedes aegypti (Diptera) when its encoding gene was expressed in an Escherichia coli host strain. The authors, Furong Tan and Jun Zhu contributed equally to this work.     

对粉纹夜蛾高毒力cry9Ea基因的克隆及表达

【目的】从本实验室分离的Bt4菌株中克隆cry9Ea基因,并研究其表达和杀虫活性。【方法】以PCR-RFLP方法鉴定Bt4菌株含有cry9基因,然后以菌株Bt4的质粒为模板,利用全长引物F9EA/R9EA进行PCR扩增全长基因。【结果】将目的片段插入到表达载体pET21b,得到大肠杆菌重组表达质粒pETcry9Ea。转化E.coli BL21(DE3),诱导后表达130kDa的蛋白,再将cry9Ea7基因连接到穿梭载体pSXY422b,电激转化HD73-(cry-),得到工程菌BioHD9Ea7,提取Cry9Ea7晶体蛋白,并进行生物活性测定。生物活性测定结果显示Cry9Ea7蛋白对粉纹夜蛾(Trichoplusia ni)初孵幼虫具有高毒力,LC50为0.044μg/mL,而对甜菜夜蛾(Spodoptera exigua)和棉铃虫(Helicoverpa armigera)初孵幼虫未显示活性。【结论】克隆和表达了一个对粉纹夜蛾高毒力的基因cry9Ea7,并成功构建了工程菌BioHD9Ea7。     

Cloning and expression of the cry1Ea4 gene of Bacillus thuringiensis and the comparative toxicity of its gene product

A new cry gene (cry1Ea4) was cloned and sequenced from a Bacillus thuringiensis isolate native to Mexico (LBIT-147). The gene coded for a 133kDa protoxin which had greater than 99% homology with the holotype Cry1Ea1, as only four mismatches were found between the two amino acid sequences. When the Cry1Ea4 toxin was expressed in a crystal-negative strain of B. thuringiensis, bipyramidal crystals were produced. Purified crystals from this recombinant strain and from the holotype (Cry1Ea1) were bioassayed against first instar larvae of the tobacco hornworm. Statistically different mean LC₅₀ values indicated that Cry1Ea4 was more toxic than its holotype. This increase in toxicity may be attributed to the three amino acids which differ from the holotype sequence in the toxic fragment.     

Susceptibility of Anthonomus grandis (cotton boll weevil) and Spodoptera frugiperda (fall armyworm) to a cry1ia-type toxin from a Brazilian Bacillus thuringiensis strain

Different isolates of the soil bacterium Bacillus thuringiensis produce multiple crystal (Cry) proteins toxic to a variety of insects, nematodes and protozoans. These insecticidal Cry toxins are known to be active against specific insect orders, being harmless to mammals, birds, amphibians, and reptiles. Due to these characteristics, genes encoding several Cry toxins have been engineered in order to be expressed by a variety of crop plants to control insectpests. The cotton boll weevil, Anthonomus grandis, and the fall armyworm, Spodoptera frugiperda, are the major economically devastating pests of cotton crop in Brazil, causing severe losses, mainly due to their endophytic habit, which results in damages to the cotton boll and floral bud structures. A cry1Ia-type gene, designated cry1Ia12, was isolated and cloned from the Bt S811 strain. Nucleotide sequencing of the cry1Ia12 gene revealed an open reading frame of 2160 bp, encoding a protein of 719 amino acid residues in length, with a predicted molecular mass of 81 kDa. The amino acid sequence of Cry1Ia12 is 99% identical to the known Cry1Ia proteins and differs from them only in one or two amino acid residues positioned along the three domains involved in the insecticidal activity of the toxin. The recombinant Cry1Ia12 protein, corresponding to the cry1Ia12 gene expressed in Escherichia coli cells, showed moderate toxicity towards first instar larvae of both cotton boll weevil and fall armyworm. The highest concentration of the recombinant Cry1Ia12 tested to achieve the maximum toxicities against cotton boll weevil larvae and fall armyworm larvae were 230 microg/mL and 5 microg/mL, respectively. The herein demonstrated insecticidal activity of the recombinant Cry1Ia12 toxin against cotton boll weevil and fall armyworm larvae opens promising perspectives for the genetic engineering of cotton crop resistant to both these devastating pests in Brazil.