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In This Article

  • Summary
  • Abstract
  • Introduction
  • Protocol
  • Representative Results
  • Discussion
  • Disclosures
  • Acknowledgements
  • Materials
  • References
  • Reprints and Permissions

Summary

Presented here is a protocol of Helicoverpa armigera (Hübner) embryo microinjection and knockout mutant identification created by CRISPR/Cas9 genome editing. Mutant insects enable further research of gene function and interaction among different genes in vivo.

Abstract

The cotton bollworm, Helicoverpa armigera, is one of the most destructive pests in the world. A combination of molecular genetics, physiology, functional genomics, and behavioral studies has made H. armigera a model species in Lepidoptera Noctuidae. To study the in vivo functions of and interactions between different genes, clustered regularly interspaced short palindromic repeats (CRISPR)/ associated protein 9 (Cas9) genome editing technology is a convenient and effective method used for performing functional genomic studies. In this study, we provide a step-by-step systematic method to complete gene knockout in H. armigera using the CRISPR/Cas9 system. The design and synthesis of guide RNA (gRNA) are described in detail. Then, the subsequent steps consisting of gene-specific primer design for guide RNA (gRNA) creation, embryo collection, microinjection, insect rearing, and mutant detection are summarized. Finally, troubleshooting advice and notes are provided to improve the efficiency of gene editing. Our method will serve as a reference for the application of CRISPR/Cas9 genome editing in H. armigera as well as other Lepidopteran moths.

Introduction

The application of genome editing technology provides an efficient tool to achieve target-gene mutants in diverse species. The emergence of the clustered regularly interspaced short palindromic repeats (CRISPR)/associated protein 9 (Cas9) system provides a novel method to manipulate genomes1. The CRISPR/Cas9 system consists of a guide RNA (gRNA) and the Cas9 endonuclease2,3, while the gRNA can be further divided into two parts, a target complementary CRISPR RNA (crRNA) and a trans-activating crRNA (tracrRNA). The gRNA integrates with Cas9 endonuclease and forms a ribonucleoprotein (RNP)....

Protocol

1. Design of gene-specific primers and preparation of sgRNA

  1. Verify a conserved genomic region in the gene of interest through PCR amplification and sequencing analyses. Amplify the target gene from the genome DNA of H. armigera and distinguish the exons and introns.
    NOTE: The sequence specificity of the guide site is necessary to avoid off-target gene editing. Search possible guide sites in the exons are close to the 5' UTR of the gene. Then, it is important to make sure that the gene is c.......

Representative Results

This protocol provides detailed steps for obtaining gene knock-out lines of H. armigera using CRISPR/Cas9 technology. The representative results obtained by this protocol are summarized for gDNA selection, embryo collection and injection, insect rearing, and mutant detection.

In this study, the target site of our gene of interest was located in its second exon (Figure 2A). This site was hig.......

Discussion

The application of the CRISPR/Cas9 system has provided powerful technical support for the analysis of gene function and interaction among various genes. The detailed protocol we present here demonstrates the generation of a homozygote mutant in H. armigera via CRISPR/Cas9 genome editing. This reliable procedure provides a straightforward way for directed gene mutagenesis in H. armigera.

The choice of CRISPR target sites could affect the mutagenesis efficiency

Disclosures

The authors do not have any conflicts of interest.

Acknowledgements

This work was supported by National Natural Science Foundation of China (31725023, 31861133019 to GW, and 31171912 to CY).

....

Materials

NameCompanyCatalog NumberComments
2kb DNA ladderTransGen BiotechBM101
Capillary GlassWorld Precision Instrucments504949referred to as "capillary glass" in the protocol
Double Sided TapeMinnesota Mining and Manufacturing Corporation665
Eppendorf FemtoJet 4i MicroinjectorEppendorf CorporateE5252000021
Eppendorf InjectMan 4 micromanipulatorEppendorf Corporate5192000051
Eppendorf Microloader Pipette TipsEppendorf CorporateG2835241
GeneArt Precision gRNA Synthesis KitThermo Fisher ScientificA29377
Microscope SlideSail Brand7105
Olympus MicroscopeOlympus CorporationSZX16
PrimeSTAR HS (Premix)Takara Biomedical TechnologyR040used for mutant detection
Sutter Micropipette PullerSutter Instrument CompanyP-1000
TIANamp Genomic DNA KitTIANGEN CorporateDP304-03
TrueCut Cas9 Protein v2Thermo Fisher ScientificA36499

References

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CRISPR Cas9Genome EditingHelicoverpa ArmigeraCotton BollwormEmbryo MicroinjectionKnockout Mutant IdentificationSgRNA Target SelectionPAM SequenceEmbryo PreparationEgg CollectionMicroinjectionCas9 ProteinSgRNA

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