Comparison of CRISPR–Cas9 Tools for Transcriptional Repression and Gene Disruption in the BEVS

The generation of knock-out viruses using recombineering of bacmids has greatly accelerated scrutiny of baculovirus genes for a variety of applications. However, the CRISPR–Cas9 system is a powerful tool that simplifies sequence-specific genome editing and effective transcriptional regulation of genes compared to traditional recombineering and RNAi approaches. Here, the effectiveness of the CRISPR–Cas9 system for gene disruption and transcriptional repression in the BEVS was compared. Cell lines constitutively expressing the cas9 or dcas9 gene were developed, and recombinant baculoviruses delivering the sgRNA were evaluated for disruption or repression of a reporter green fluorescent protein gene. Finally, endogenous AcMNPV genes were targeted for disruption or downregulation to affect gene expression and baculovirus replication. This study provides a proof-of-concept that CRISPR–Cas9 technology may be an effective tool for efficient scrutiny of baculovirus genes through targeted gene disruption and transcriptional repression.

Double-Stranded RNA-Degrading Enzymes Reduce the Efficiency of RNA Interference in Plutella xylostella

DsRNA-degrading enzymes (dsRNases) have been recognized as important factors in reducing RNA interference (RNAi) efficiency in different insect species. However, dsRNases in Plutella xylostella are still unknown. We identified the full-length cDNAs of PxdsRNase1, PxdsRNase2, PxdsRNase3, and PxdsRNase4. Gene expression profile showed that PxdsRNase1 was mainly expressed in the hemolymph; and that PxdsRNase2 and PxdsRNase3 were mainly expressed in the intestinal tract. The expression of PxCht (Chitinase of P. xylostella) in P. xylostella larvae injected with the mixture of dsPxCht (dsRNA of PxCht) and dsPxdsRNase1 (dsRNA of PxdsRNase1), dsPxdsRNase2 (dsRNA of PxdsRNase2), or dsPxdsRNase3 (dsRNA of PxdsRNase3) was significantly higher than that in the larvae injected with the mixture of dsGFP (dsRNA of green fluorescent protein gene, GFP) and dsPxCht; the transcription level of PxCht in the larvae feeding on the mixture of dsPxCht and dsPxdsRNase1, dsPxdsRNase2, or dsPxdsRNase3 was significantly higher than that in the larvae feeding on the mixture of dsPxCht and dsGFP. The recombinant protein of PxdsRNase1 degraded dsRNA rapidly, PxdsRNase3 cleaved dsRNA without complete degradation, and PxdsRNase2 could not degrade dsRNA in vitro. These results suggested that PxdsRNases1, PxdsRNases2, and PxdsRNases3 were involved in the dsRNA degradation to reduce RNAi efficiency with different mechanisms.

Involvement of FLOWERING LOCUS T in microgravity response of Arabidopsis thaliana plants under long- and short-day conditions

Microgravity have an impact on growth and development of higher plants in space at both vegetative stage and reproductive stage. A great deal of information has been available on the vegetative stage in space, but relatively little is known about the influence of microgravity on plants at the reproductive stage. In this study, we constructed a transgenic Arabidopsis thaliana plants expressing flowering control gene, FLOWERING LOCUS T (FT), together with green fluorescent protein gene(GFP) under control of a heat shock-inducible promoter (HSP17.4), by which we induced FT expression inflight through remote controlling heating shock treatment. Inflight photography data showed that induction of FT expression in plants in space could counteract the impact of microgravity and promote flowering. Whole-genome microarray analysis of gene expression changes in leaves of wild-type and these transgenic plants grown under different photoperiod conditions in space indicated that the function of the photoperiod-related microgravity response genes are mainly involved in protein synthesis and post-translation protein modulation, notably protein phosphorylation. In addition, changes of circadian component gene expression in response to microgravity under different photoperiod indicated that role of circadian oscillator could act as integrators of microgravity response and photoperiodic signals in Arabidopsis plant grown in space.

Enhancing the Protective Immune Response to Administration of a LIVP-GFP Live Attenuated Vaccinia Virus to Mice

Following the WHO announcement of smallpox eradication, discontinuation of smallpox vaccination with vaccinia virus (VACV) was recommended. However, interest in VACV was soon renewed due to the opportunity of genetic engineering of the viral genome by directed insertion of foreign genes or introduction of mutations or deletions into selected viral genes. This genomic technology enabled production of stable attenuated VACV strains producing antigens of various infectious agents. Due to an increasing threat of human orthopoxvirus re-emergence, the development of safe highly immunogenic live orthopoxvirus vaccines using genetic engineering methods has been the challenge in recent years. In this study, we investigated an attenuated VACV LIVP-GFP (TK-) strain having an insertion of the green fluorescent protein gene into the viral thymidine kinase gene, which was generated on the basis of the LIVP (Lister-Institute for Viral Preparations) strain used in Russia as the first generation smallpox vaccine. We studied the effect of A34R gene modification and A35R gene deletion on the immunogenic and protective properties of the LIVP-GFP strain. The obtained data demonstrate that intradermal inoculation of the studied viruses induces higher production of VACV-specific antibodies compared to their levels after intranasal administration. Introduction of two point mutations into the A34R gene, which increase the yield of extracellular enveloped virions, and deletion of the A35R gene, the protein product of which inhibits presentation of antigens by MHC II, enhances protective potency of the created LIVP-TK--A34R*-dA35R virus against secondary lethal orthopoxvirus infection of BALB/c mice even at an intradermal dose as low as 103 plaque forming units (PFU)/mouse. This virus may be considered not only as a candidate attenuated live vaccine against smallpox and other human orthopoxvirus infections but also as a vector platform for development of safe multivalent live vaccines against other infectious diseases using genetic engineering methods.

Targeted Gene Integration into Nuclear Genome of Microalgae Using Cre/loxP Recombination System

Genetically modified microalgae have been expected to be a useful tool for bioenergy and recombinant protein production. However, random integration of transgene in the microalgae nuclear genome is susceptible to gene silencing of heterologous gene expression. Here, we attempted to perform targeted gene integration into a pre-determined nuclear genomic site of Chlamydomonas reinhardtii using Cre/loxP recombination system for stable transgene expression. We constructed an expression vector plasmid encoding reporter genes (zeocin resistant gene and green fluorescent protein gene; Zeo-2A-GFP) and mutated loxP to generate founder cells. A donor vector encoding IFNα-4 and paromomycin resistant genes flanked by corresponding mutated loxPs was constructed and introduced into founder cells together with a Cre expression vector. The optimal ratio of donor vector to Cre expression vector was determined by counting the number of paromomycin resistant colonies. For the established clones, the targeted integration was confirmed by genomic PCR using various specific primer sets. Target genes in the donor vector could be integrated into the expected genomic site of C. reinhardtii using Cre/loxP system. RT-PCR revealed that IFNα-4 was expressed in five independent transgenic cell lines tested. This result suggests that Cre-based cell engineering is a promising approach to generate smart microalgae expressing foreign genes.

A Stable Agrobacterium rhizogenes-Mediated Transformation of Cotton (Gossypium hirsutum L.) and Plant Regeneration From Transformed Hairy Root via Embryogenesis

Genetic transformation is a powerful tool to study gene function, secondary metabolism pathways, and molecular breeding in crops. Cotton (Gossypium hirsutum L.) is one of the most important economic crops in the world. Current cotton transformation methods take at least seven to culture and are labor-intensive and limited to some cultivars. In this study, we first time achieved plantlet regeneration of cotton via embryogenesis from transformed hairy roots. We inoculated the cotyledon explants of a commercial cultivar Zhongmian-24 with Agrobacterium rhizogenes strain AR1193, harboring a binary vector pBI-35S::GFP that contained the NPT II (neomycin phosphotransferase) gene and the GFP (green fluorescent protein) gene as a fluorescent marker in the T-DNA region. 82.6% explants produced adventitious roots, of which 53% showed GFP expression after transformation. 82% of transformed hairy roots produced embryonic calli, 12% of which regenerated into stable transformed cotton plants after 7 months of culture. The integration of GFP in the transformed cotton genomes were confirmed by PCR (Polymerase chain reaction) and Southern blot analysis as well as the stable expression of GFP were also detected by semi-quantitative RT-PCR analysis. The resultant transformed plantlets were phenotypically, thus avoiding Ri syndrome. Here we report a stable and reproducible method for A. rhizogenes-mediated transformation of cotton using cotyledon as explants, which provides a useful and reliable platform for gene function analysis of cotton.

Efficient and Genotype Independent Maize pollen Transfection Mediated by Magnetic Nanoparticles

Background: Biotechnological engineering of maize to introduce favorable new traits relies on delivery of foreign DNA into its cells. Current gene delivery methods for maize is limited to specific genotypes, and depend on time-consuming and labor-intensive processes of tissue culture. Results: Here, we report a new method to transfect maize that is culture-free and genotype independent. Enhanced green fluorescent protein gene (EGFP) or bialaphos resistance gene (Bar) bound with magnetic nanoparticles (MNPs) was delivered into maize pollens, and female florets of five maize varieties were pollinated. Green fluorescence was detected in 92% transfected pollens and 70% immature embryos. EGFP gene detected by PCR ranged from 29 to 68% in T1 generation of these five transfected varieties, and 7-16% of the T1 seedlings showed immunologically active EGFP protein. Moreover, 1.41% of the Bar transfected T1 plants were glufosinate resistant, and heritable Bar gene was integrated into the maize genome effectively (verified by Southern blot), expressed normally and inherited stably in their progenies.Conclusion: These results demonstrate that exogenous DNA could be delivered into maize efficiently and expressed normally through our genotype-independent pollen transfection system, providing a reliable, fast and large-scale gene delivery choice for most elite maize varieties recalcitrant to tissue culture.

Strategy for modification of the bovine beta-lactoglobulin geneusing components of the CRISPR/Cas9 system in plasmid form

Using on-line programs, sites were selected for obtaining double-stranded breaks in the BLG gene of cattle. The strategy for making double-stranded cuts in the BLG gene was developed taking into account the polymorphic variant of the gene (A-allele): DNA was isolated from bovine sperm used for fertilization of cow eggs in vitro. Four pX330 plasmids encoding Cas9 endonuclease and gRNAs specific to the selected BLG gene sequences were obtained. A strategy was developed for analyzing possible genetic modifications resulting from the operation of the CRISPR/Cas9 system components and the genetic construct microinjected into zygotes (NHEJ, HDR). The pBLGcmvEGFP plasmid containing the green fluorescent protein gene under the cytomegalovirus promoter was proposed as a model genetic construct for replacing the BLG gene. The use of a plasmid containing the reporter protein gene under its own regulatory sequences, flanked by homology arms to the beta-lactoglobulin gene, can be useful for evaluating the effectiveness of site-specific activity of the CRISPR/Cas9 system components in vitro.

New models to study plasma cells in mouse based on the restriction of IgJ expression to antibody secreting cells

ABSTRACTPlasma cells (PC) represent the last stage of B cell development and are mainly characterized by their capacity of secreting large quantities of antibodies. They can be implicated in a broad-spectrum of neoplastic disorders, including Multiple Myeloma, Waldenstrom macroglobulinemia or Monoclonal Gammopathy of Clinical Significance, all characterized by the abnormal proliferation of a PC clone. Up to date, there are only few reporter models to specifically follow PC development, migration and homing in mouse and none allowing the genetic manipulation of these cells. We created a transgenic mouse model in which a green fluorescent protein gene was placed under the control of the well-characterized regulatory elements of the murine immunoglobulin J (IgJ) chain locus. Thanks to this model, we demostrated that IgJ is an early and specific marker of antibody secreting cells (ASCs) and appears before the expression of CD138, making it a good candidate to targeted genetic modifications of plasma cells. Therefore, a conditional deletion model using a Tamoxifen-dependent Cre recombinase inserted into the IgJ locus was characterized. Using a reporter model, we showed that, in contrast with existing models of B cell lineage genetic modification, the activity of the CRE recombinase only affects ASCs after tamoxifen treatment. Additionally, we used this model in a functional in vitro assay, to show that Ig modifications directly affect plasma cell survival. These two new mouse models, IgJGFP and IgJCreERT2 represent exquisite tools to study PCs. In pathology, the IgJCreERT2model opens new frontiers for in vivo genetic modifications of PCs to better reflect the pathophysiology of PC-related diseases.

Genetically modified rabbits as bio-producers and biomodels

Genetically modified (GM) animals are necessary to solve the global problems of humanity related to nutrition and health. Rabbits, as laboratory, domestic and farm animals, occupy a special niche in research. GM rabbits are promising as bioreactors for producing biologically active (BA) proteins with milk or blood, and are in demand in Biomedicine as biomodels of diseases. To date, many GM rabbits-biomodels, producers of recombinant proteins have been created in the world using CRISPR/Cas9 technology. All-Russian Research Institute of Animal Physiology, Biochemistry and Nutrition has experience in obtaining transgenic rabbitsproducers of human BA proteins with milk by microinjecting recombinant DNA into zygote pronuclei. The possibility of site-specific modification of the rabbit whey acidic protein (WAP) gene using CRISPR/Cas9 technology is discussed. A DNA matrix containing homology arms to the WAP rabbit gene and site-specific CRISPR/Cas9 components in plasmid form were obtained. Microinjections of rabbit zygotes were performed and embryo survival was evaluated in vitro. The efficiency of using the green fluorescent protein gene under the cytomegalovirus promoter in the DNA matrix as an indicator of homologically directed repair was evaluated. This work can be useful for obtaining rabbits that produce with milk BA protein instead of WAP.