Fighting agricultural and health pests by genetically modifying the insects that cause them is already possibleand also with simple methods, as demonstrated by an international team with the presence of Spanish scientists.
An international team led by members of the University of Kyoto, with the participation of the Institute of Evolutionary Biology (IBE-CSIC-UPF), has developed a technique that makes it possible to easily edit genes in insects. Called direct parental CRISPR (DIPA-CRISPR, from the English Direct Parental CRISPR)this action implies the injection of the Cas9-gRNA complex in adult females that are maturing eggs to achieve genetic modification of future embryos. The study, published in the journal Cell Reports Methodsopens the door to editing the genome of insect species, facilitating studies in basic research, as well as its possible use in the control of agricultural and health pests.
With more than a million described species, insects are a treasure of biodiversity and represent a powerful research tool. Gene editing of this large group may be key to answering some fundamental questions in biology, and also to implement pest control measures in the field of agriculture and global health.
“Current techniques for insect gene editing generally require the microinjection of materials into early embryos, seriously limiting their application to many species. For example, previous studies have failed to gene edit cockroaches due to their reproductive strategy.” Furthermore, insect gene editing often requires expensive equipment, a species-specific experimental design, and highly-skilled laboratory personnel,” the study authors note.
To overcome these limitations, an international team led by members of Kyoto University, made up of researchers from that university and the Institute of Evolutionary Biology (IBE), a mixed center of the CSIC and Pompeu Fabra University (UPF), has established a Simple and efficient CRISPR-Cas9 method for insect gene editing by injection of adult females. The technique could be easily implemented in any laboratory and applied directly to a wide variety of insects.Tested on two insects
The team used DIPA-CRISPR to successfully modify genes of the German cockroach (Blattella germanica). The technique involves injecting the Cas9-gRNA complex into the body cavity of adult females to introduce hereditary mutations into the developing eggs. This novel approach will allow researchers using insects as experimental models to free themselves from the technical difficulty of injecting the eggs.
The results showed that the gene editing efficiency of Blattella germanica could reach 22%. In it small flour beetle (Tribolium castaneum), DIPA-CRISPR achieved an efficiency of more than 50%. The successful application of DIPA-CRISPR in two evolutionarily distant species demonstrates its potential for very wide use.
“The German cockroach, a model widely used in research, encapsulates the eggs in a rigid shell – the ootheca – making it practically impossible to inject the eggs, as is commonly done with CRISPR procedures. The design we propose consists of applying the genetic scissors in reproductive females. The injected components penetrate the growing oocytes and will affect the embryos”, explains Xavier Bellés, a researcher at the Institute of Evolutionary Biology (IBE) in the Evolution of insect metamorphosis laboratory, and a participant in the study.
The experiments showed that the most critical parameter for success is injecting the CRISPR components when the female is in the middle of her reproductive cycle. “DIPA-CRISPR requires a good understanding of ovarian development. This can be challenging in some species, given the diverse reproductive strategies of insects”comments Maria Dolors Piulachs, IBE principal investigator in the Insect Reproduction laboratory, and a participant in the study.
Despite these limitations, DIPA-CRISPR is affordable, highly practical and could be easily implemented in laboratories, extending the application of gene editing to a wide diversity of insect species. The technique requires minimal equipment for injection in adults, and only two components, the Cas9 protein and unmodified guide RNA, greatly simplifying gene editing procedures.
“Being able to use DIPA-CRISPR on a regular basis in the laboratory will allow us a deeper understanding of the function of some genes”, he points out Piulachswho previously led a patronage campaign on the “Precipita” platform to develop this technique, and who contributed to the first steps of this study.
The development of DIPA-CRISPR opens the door to future genome editing of other arthropods using a similar approach. These include agricultural and medical pests such as mites and ticks, and important fishery resources such as shrimp and crabs.
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