Microinjection of Corn Planthopper, Peregrinus maidis, Embryos for CRISPR/Cas9 Genome Editing
March 26th, 2021
4.3K views
Herein are protocols for collecting and microinjecting precellular corn planthopper embryos for the purpose of modifying their genome via CRISPR/Cas9-based genome editing or for the addition of marked transposable elements through germline transformation.
Overview
This article presents a detailed protocol for CRISPR/Cas9-mediated genome editing in the corn planthopper, Peregrinus maidis, a significant pest and vector of maize viruses. The method enables efficient collection and microinjection of precellular embryos, facilitating both gene knockout and potential germline transformation. The approach is adaptable to other Hemipteran species and offers a foundation for developing stable mutant strains for functional genomics and pest management.
Key Study Components
Area of Science
- Entomology
- Genetics
- Genome Editing
- Pest Management
Background
- P. maidis is a major pest of maize and transmits several maize viruses.
- RNA interference (RNAi) via dsRNA microinjection has been used but produces only transient phenotypes.
- Stable, heritable genetic modifications are needed for advanced functional studies and pest control.
- CRISPR/Cas9 genome editing requires precise embryo microinjection before cellularization.
Purpose of Study
- To develop and detail a protocol for CRISPR/Cas9-based genome editing in P. maidis embryos.
- To enable the production of stable mutant and potentially transgenic lines.
- To provide a method adaptable to other Hemipteran pests.
Methods Used
- Construction of an adult insect chamber for controlled egg laying.
- Timed collection of embryos using an agarose-based egg-lay method.
- Microinjection of Cas9-guide RNA complexes into precellular embryos using beveled quartz needles.
- Post-injection embryo care, hatching, and rearing under controlled conditions.
- Screening for gene knockout phenotypes and establishment of homozygous lines.
Main Results
- Efficient collection and microinjection of P. maidis embryos was achieved.
- Cas9 injection did not adversely affect overall development or hatch rates compared to controls, though guide RNA injection reduced hatch rates.
- Approximately 30% knockout efficiency was observed for the targeted eye-color gene (white locus), confirmed by pigment loss and PCR analysis.
- The protocol was successfully adapted for use in thrips embryos and is potentially applicable to other Hemipterans.
Conclusions
- This protocol enables stable genome editing and potential germline transformation in P. maidis.
- It provides a foundation for advanced genetic studies and novel pest management strategies.
- The method is adaptable to other insect species sensitive to desiccation and can facilitate the development of transgenic lines.
Frequently Asked Questions
What is the main advantage of using CRISPR/Cas9 in P. maidis compared to RNAi?
CRISPR/Cas9 enables stable, heritable gene modifications, whereas RNAi produces only transient, non-inheritable phenotypes.
Why is the timing of embryo injection critical in this protocol?
CRISPR/Cas9 components must be delivered before embryo cellularization to ensure genome editing occurs in all cells, including the germline.
How are embryos collected for microinjection?
Embryos are collected from females using an agarose-based egg-lay method and transferred to double-sided tape on a cover slip for microinjection.
What gene was targeted in the representative experiment, and how was knockout confirmed?
The eye-color gene (white locus) was targeted. Knockout was confirmed by pigment loss and PCR analysis of genomic DNA.
Can this protocol be used for other Hemipteran species?
Yes, the protocol is adaptable and has shown promising results in other species such as thrips.
What are the potential applications of generating transgenic planthoppers?
Transgenic planthoppers could be used for novel pest control strategies, such as creating insects unable to transmit viruses, reducing reliance on insecticides.
What tips are provided to improve embryo survival during microinjection?
Using beveled needles minimizes trauma, and continued practice with the technique increases embryo survival rates.
Executive Industry Relevance
Stable genome editing in Peregrinus maidis embryos via CRISPR/Cas9 microinjection enables functional genomics and the creation of heritable mutant lines in a key agricultural pest. This capability supports predictive confidence in target validation and mechanistic de-risking for pest management strategies. The protocol's adaptability to other Hemipterans positions it as a reusable platform for translational research and pipeline innovation.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Enables interrogation of gene function through stable knockout and heritable trait analysis.
- Supports mechanistic de-risking by allowing direct assessment of gene-phenotype relationships.
- Facilitates predictive confidence in target selection for pest control interventions.
Screening & Assay Development
- Prepares validated mutant lines for downstream phenotypic screening and compound evaluation.
- Standardizes embryo microinjection and recovery workflows for reproducibility across experiments.
- Generates quantitative outputs such as knockout efficiency and phenotype penetrance.
Translational & Preclinical Research
- Aligns genetic manipulation with translational biomarker development in pest species.
- Enables continuity from gene editing to functional validation in disease-relevant systems.
- Supports risk-adjusted advancement of genetic pest management strategies.
Pipeline & Workflow Integration
This microinjection protocol integrates at the interface of early discovery and translational research, enabling progression from hypothesis testing to preclinical validation in pest genomics.
- Discovery Biology: Provides a platform for hypothesis-driven gene function studies and pathway elucidation.
- Screening: Delivers reproducible, quantitative knockout lines for assay development and screening readiness.
- Analytics: Supplies measurable outputs such as gene disruption rates and phenotypic confirmation via PCR and visual screening.
- Translational Research: Bridges discovery and application by enabling germline transformation and trait propagation.
- Enterprise Reuse: Offers a flexible, adaptable workflow for genome editing across multiple Hemipteran species.
Operational & Enterprise Impact
- Scientific Value: Increases predictive confidence and reduces mechanistic ambiguity in gene function studies.
- Operational Value: Standardizes microinjection and embryo handling for scalable, reproducible outcomes.
- Strategic Value: Improves go/no-go decisions for genetic pest management and functional genomics programs.
- Portfolio Impact: Enables risk-adjusted prioritization of genetic targets and advancement of transgenic lines.
Implementation Considerations
- Requires expertise in embryo handling, microinjection, and insect rearing.
- Needs specialized equipment such as beveled quartz needles and humidified chambers.
- Demands cross-team standardization for reproducibility and data comparability.
- Adaptable to other desiccation-sensitive insect embryos with protocol optimization.
- Embryo survival and knockout efficiency depend on technical proficiency and needle quality.
Biopharma FAQs
Why does null hypothesis testing matter for CRISPR knockout validation?
Null hypothesis testing ensures that observed phenotypic changes in CRISPR-edited P. maidis embryos are statistically attributable to targeted gene disruption, supporting robust target validation and reducing mechanistic ambiguity in functional genomics pipelines.
How does independent variable isolation fit embryo microinjection workflows?
Isolating variables such as injection buffer composition and guide RNA presence allows teams to attribute developmental and phenotypic outcomes specifically to genome editing, enhancing experimental clarity and workflow reproducibility.
What do quantitative dependent variable measurements enable in gene editing?
Quantitative measurements, such as knockout efficiency and hatch rates, provide actionable data for comparing experimental conditions, optimizing protocols, and informing go/no-go decisions in genetic pest management research.
Why are replication requirements critical for cross-functional collaboration?
Replication of embryo microinjection and phenotype screening ensures that results are reproducible across teams and settings, supporting cross-functional data integration and enterprise-wide confidence in genetic tool deployment.
What statistical analysis capabilities are required before protocol implementation?
Teams must be able to analyze knockout rates, phenotype penetrance, and developmental outcomes using appropriate statistical methods to validate protocol performance and support risk-adjusted advancement decisions in R&D pipelines.
Chapters in this video
0:04
Introduction
1:08
Preparation of Agarose‐Based Egg‐Lay Chamber
2:23
Embryo Collection and Alignment
2:59
Microinjection and Post‐Injection Care
3:48
Incubation and Hatching of Embryos
5:03
Results: Microinjection of P. maidis Embryos for CRISPR/Cas9 Genome Editing and Collection
6:32
Conclusion
