Nutrient conditions determine the localization of <i>Bacillus thuringiensis</i> Vip3Aa protein in the mother cell compartment

Wang, Zeyu; Gan, Chunxia; Wang, Jian; Bravo, Alejandra; Soberón, Mário; Yang, Qing; Zhang, Jie

doi:10.1111/1751-7915.13719

Cited by 14 publications

(9 citation statements)

References 31 publications

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“…Therefore, we assume that the results we describe in this study should be valid for all these B. thuringiensis strains. This claim agrees with a result showing that in B. thuringiensis strain KN11, Vip3A is specifically produced during the stationary phase and accumulates in the cytoplasm of bacteria grown in twofold diluted LB medium (35). The production of Vip3A during vegetative growth (12) and the weak vip3A expression we observed during the exponential growth phase (Fig.…”

Section: Discussionsupporting

confidence: 92%

Expression of the Bacillus thuringiensis vip3A insecticidal toxin gene is activated at the onset of stationary phase by VipR, an autoregulated transcription factor

Chen

Verplaetse

Slamti

et al. 2022

Preprint

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The Vegetative insecticidal protein Vip3A is produced by some Bacillus thuringiensis strains from the mid-log growth phase to sporulation. Although Vip3A is important for the entomopathogenicity of B. thuringiensis, the vip3A gene regulation is unknown. In the B. thuringiensis kurstaki HD1 strain, vip3A is carried by the pBMB299 plasmid, which is absent in the closely related strain B. thuringiensis kurstaki HD73. Using a transcriptional fusion between the vip3A promoter and lacZ, we observed that the HD73 strain is unable to express vip3A. This result suggests that a specific regulator is required for vip3A expression. Assuming that the regulator gene is located on the same plasmid as vip3A, we transferred the pBMB299 from the HD1 strain to the HD73 strain. We found that Vip3A was produced in the HD73 strain containing pBMB299, suggesting that the regulator gene is located on this plasmid. Using this heterologous host and promoter-lacZ transcription fusions, we confirmed that VipR is essential to activate vip3A expression at the onset of stationary phase. We demonstrated that vipR transcription is positively autoregulated and the determination of the vipR and vip3A promoters pinpointed a putative VipR target upstream from the Sigma A-specific −10 region of these two promoters. Surprisingly, this conserved sequence was also found upstream of cry1I and cry2 genes. Finally, we showed that vip3A and vipR expression is drastically increased in a Δspo0A mutant unable to initiate sporulation. In conclusion, we have characterized a novel regulator involved in the entomopathogenic potency of B. thuringiensis through a sporulation-independent pathway.ImportanceThe insecticidal properties of Bacillus thuringiensis are mainly due to Cry toxins which form a crystalline inclusion during sporulation. However, other proteins participate in the pathogenicity of the bacterium, notably the Vip3A toxins that are produced from vegetative growth to sporulation. The VipR regulator that activates vip3A gene expression at the onset of stationary phase is positively autoregulated and analysis of the promoter region of the vip3A and vipR genes reveals the presence of a highly conserved DNA sequence. This possible VipR target sequence is also found upstream of the cry2A and cry1I genes, suggesting that Cry toxins can be produced before the bacteria enter sporulation. Such a result could allow us to better understand the role of Cry and Vip3A toxins during the B. thuringiensis infectious cycle in insects, in addition to the primary role of the Cry toxins in the toxemia caused by ingestion of crystals.

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Section: Discussionsupporting

confidence: 92%

Expression of the Bacillus thuringiensis vip3A insecticidal toxin gene is activated at the onset of stationary phase by VipR, an autoregulated transcription factor

Chen

Verplaetse

Slamti

et al. 2022

Preprint

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show abstract

“…Therefore, we assume that the results we describe in this study should be valid for all these B. thuringiensis strains. This claim agrees with a result showing that in B. thuringiensis strain KN11, Vip3A is produced specifically during the stationary phase and accumulates in the cytoplasm of bacteria grown in 2-fold-diluted LB medium ( 35 ). The production of Vip3A during vegetative growth ( 12 ) and the weak vip3A expression we observed during the exponential growth phase ( Fig.…”

Section: Discussionsupporting

confidence: 92%

Expression of the Bacillus thuringiensis vip3A Insecticidal Toxin Gene Is Activated at the Onset of Stationary Phase by VipR, an Autoregulated Transcription Factor

et al. 2022

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“…In addition, Wang et al [ 30 ] reported that Vip3Aa secretion is nutrient-dependent. When grown in a sporulation medium, Vip3Aa were not secreted to the culture solution but were retained in the mother cell compartment.…”

Section: Discussionmentioning

confidence: 99%

Vegetative Insecticidal Protein Vip3Aa Is Transported via Membrane Vesicles in Bacillus thuringiensis BMB171

Zhang

Tian

et al. 2022

Toxins

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Vegetative insecticidal protein Vip3Aa, secreted by many Bacillus thuringiensis (Bt) strains during the vegetative growth stage, represents the second-generation insecticidal toxin. In recent years, significant progress has been made on its structure and action mechanism. However, how it is translocated across the cytoplasmic membrane into the environment remains a mystery. This work demonstrates that Vip3Aa is not secreted by the General Secretion (Sec) System. To reveal the secretory pathway of Vip3A, we purified the membrane vesicles (MVs) of B. thuringiensis BMB171 and observed by TEM. The size of MVs was determined by the dynamic light scattering method, and their diameter was approximately 40–200 nm, which is consistent with the vesicles in Gram-negative bacteria. Moreover, Vip3A could be detected in the purified MVs by Western blot, and immunoelectron microscopy reveals Vip3A antibody-coated gold particles located in the MVs. After deleting its signal peptide, chitinase B (ChiB) failed to be secreted. However, the recombinant ChiB, whose signal peptide was substituted with the N-terminal 39 amino acids from Vip3A, was secreted successfully through MVs. Thus, this sequence is proposed as the signal region responsible for vesicle transport. Together, our results revealed for the first time that Vip3Aa is transported to the medium via MVs.

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Nutrient conditions determine the localization of Bacillus thuringiensis Vip3Aa protein in the mother cell compartment

Cited by 14 publications

References 31 publications

Expression of the Bacillus thuringiensis vip3A insecticidal toxin gene is activated at the onset of stationary phase by VipR, an autoregulated transcription factor

Expression of the Bacillus thuringiensis vip3A insecticidal toxin gene is activated at the onset of stationary phase by VipR, an autoregulated transcription factor

Expression of the Bacillus thuringiensis vip3A Insecticidal Toxin Gene Is Activated at the Onset of Stationary Phase by VipR, an Autoregulated Transcription Factor

Vegetative Insecticidal Protein Vip3Aa Is Transported via Membrane Vesicles in Bacillus thuringiensis BMB171

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