Assay and characterization of an osmolarity inducible promoter newly isolated from Bacillus subtilis

Identification of an anther-specific promoter from a male sterile AB line in Chinese cabbage (Brassica rapa L. ssp. pekinensis)

The promoter of the male sterile gene is important for studying male sterility. In this study, BraA08g014780.3C which differentially expressed between male sterile and fertile plants was identified from a genetic male sterile AB line of Chinese cabbage by RNA-seq. qRT-PCR revealed that BraA08g014780.3C was mainly expressed in the early stage of floral bud development in fertile plants, and preferentially expressed in their anthers. The promoter of BraA08g014780.3C was cloned and analyzed. Cis acting element analysis showed that the promoter of BraA08g014780.3C contains POLLEN1LELAT52 and GTGANTG10, which are both pollen-specific expression elements. The BraA08g014780.3Cp::GUS vector was constructed, then transformed to Arabidopsis thaliana Col-0. PCR analysis and sequencing of the transgenic Arabidopsis revealed that the GUS gene driven by the BraA08g014780.3C promoter was successfully transformed to the Arabidopsis. GUS staining indicated that the promoter of BraA08g014780.3C was an anther-specific promoter. Identifying the anther-specific promoter laid a foundation for revealing BraA08g014780.3C function in male sterility of Chinese cabbage.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03160-z.

An overview and future prospects of recombinant protein production in Bacillus subtilis

Bacillus subtilis is a well-characterized Gram-positive bacterium and a valuable host for recombinant protein production because of its efficient secretion ability, high yield, and non-toxicity. Here, we comprehensively review the recent studies on recombinant protein production in B. subtilis to update and supplement other previous reviews. We have focused on several aspects, including optimization of B. subtilis strains, enhancement and regulation of expression, improvement of secretion level, surface display of proteins, and fermentation optimization. Among them, optimization of B. subtilis strains mainly involves undirected chemical/physical mutagenesis and selection and genetic manipulation; enhancement and regulation of expression comprises autonomous plasmid and integrated expression, promoter regulation and engineering, and fine-tuning gene expression based on proteases and molecular chaperones; improvement of secretion level predominantly involves secretion pathway and signal peptide screening and optimization; surface display of proteins includes surface display of proteins on spores or vegetative cells; and fermentation optimization incorporates medium optimization, process condition optimization, and feeding strategy optimization. Furthermore, we propose some novel methods and future challenges for recombinant protein production in B. subtilis.Key points• A comprehensive review on recombinant protein production in Bacillus subtilis.• Novel techniques facilitate recombinant protein expression and secretion.• Surface display of proteins has significant potential for different applications.

Trehalose Production Using Recombinant Trehalose Synthase in Bacillus subtilis by Integrating Fermentation and Biocatalysis

Trehalose, a stable nonreducing disaccharide, protects biomolecules against environmental stress. However, trehalose production using secretory trehalose synthase (TreS) by Bacillus subtilis has not been well studied. In this study, a mutant TreS was successfully secreted and expressed in B. subtilis WB800N. The extracellular enzyme activity of TreS regulated by the P₄₃ promoter and SP_PhoD signal peptide in recombinant B. subtilis WB800N reached 23080.6 ± 1119.4 U/L in a 5-L fermenter after optimizing the culture medium, while xpF, skfA, lytC, and sdpC were knocked out. To reduce maltose consumption, malP and amyE corresponding to maltose transporters were further deleted. To simplify the trehalose production process, we invented a fermentation-coupling biocatalysis process involving recombinant bacteria fermentation to secrete TreS and simultaneous conversion of maltose to trehalose by TreS and found that the conversion rate of maltose to trehalose reached 75.5%, suggesting that this is an efficient strategy for large-scale trehalose production using recombinant B. subtilis.

Saturation mutagenesis and self-inducible expression of trehalose synthase in Bacillus subtilis

Trehalose is a nonreducing disaccharide synthesized by trehalose synthase (TreS), which catalyzes the reversible interconversion of maltose and trehalose. We aimed to enhance the catalytic conversion of maltose to trehalose by saturation mutagenesis, and constructed a self-inducible TreS expression system by generating a robust Bacillus subtilis recombinant. We found that the conversion yield and enzymatic activity of TreS was enhanced by saturation mutations, especially by the combination of V407M and K490L mutations. At the same time, these saturation mutations were contributing to reducing by-products in the reaction. Compared to WT TreS, the conversion yield of maltose to trehalose was increased by 11.9%, and the k_cat /K_m toward trehalose was 1.33 times higher in the reaction catalyzed by treS^V407M-K490L . treS^V407M-K490L expression was further observed in the recombinant B. subtilis W800N(Δσ^F ) under the influence of P_srfA , P_cry3Aa , and P_srfA-cry3Aa promoters without an inducer. It was shown that P_srfA-cry3Aa was evidently a stronger promoter for treS^V407M-K490L expression, with the intracellular enzymatic activity of recombinant treS^V407M-K490L being over 5,800 U/g at 35 hr in TB medium. These results suggested the combination of two mutations, V407M and K490L, was conducive for the production of trehalose. In addition, the self-inducible TreS^V407M/K490L mutant in the B. subtilis host provides a low-cost choice for the industrial production of endotoxin-free trehalose with high yields.

GmPRP2 promoter drives root-preferential expression in transgenic Arabidopsis and soybean hairy roots

BACKGROUND

Promoters play important roles in gene expression and function. There are three basic types of promoters: constitutive, specific, and inducible. Constitutive promoters are widely used in genetic engineering, but these promoters have limitations. Inducible promoters are activated by specific inducers. Tissue-specific promoters are a type of specific promoters that drive gene expression in specific tissues or organs. Here, we cloned and characterized the GmPRP2 promoter from soybean. The expression pattern indicated that this promoter is root-preferential in transgenic Arabidopsis and the hairy roots of soybean. It can be used to improve the root resistance or tolerance to pathogens, pests, malnutrition and other abiotic stresses which cause extensive annual losses in soybean production.

RESULTS

The GmPRP2 promoter (GmPRP2p-1062) was isolated from soybean cv. Williams 82. Sequence analysis revealed that this promoter contains many cis-acting elements, including root-specific motifs. The GmPRP2p-1062 and its 5'-deletion fragments were fused with the GUS reporter gene and introduced into Arabidopsis and the hairy roots of soybean to further determine promoter activity. Histochemical analysis in transgenic Arabidopsis showed that GUS activity was mainly detected in roots and hypocotyls in all deletion fragments except GmPRP2p-471 (a 5'-deletion fragment of GmPRP2p-1062 with 471 bp length). GUS activity was higher in transgenic Arabidopsis and hairy roots with GmPRP2p-1062 and GmPRP2p-852 (a 5'-deletion fragment of GmPRP2p-1062 with 852 bp length) constructs than the other two constructs. GUS activity was enhanced by NaCl, PEG, IAA and JM treatments and decreased by SA, ABA and GA treatments in transgenic Arabidopsis.

CONCLUSIONS

GmPRP2p-1062 is a root-preferential promoter, and its core fragment for root-preferential expression might lie between -369 and +1. GmPRP2p-852 may be useful in the genetic engineering of novel soybean cultivars in the future.