CRISPR/Cas9: A New Genetic Strategy Against the Diamondback Moth

 By: Alezandra Patriz DL. Aragon | Fosmid

The diamondback moth (Plutella xylostella) has been a stubborn foe in the field of farmers. It is even considered the most damaging insect pest to Brassica crops worldwide and is also a major canola pest that can be found anywhere there are cruciferous hosts. Farmers fight back, often with the use of insecticides, and scientists now are fighting it with the use of CRISPR-Cas9.

But first, what does CRISPR mean? CRISPR is an acronym for Clustered Regularly Interspaced Short Palindromic Repeats. It can cleave DNA and is a part of bacterial immune systems. But, it has been modified to be used as a gene editing tool. It functions as an accurate set of molecular scissors that, when guided by a configurable guide, may cut a target DNA sequence.

The CRISPR-Cas9 system has two main components. These are: 

• Cas9 enzymes that act as a pair of molecular scissors that cut both strands of DNA at a specific site in the genome. After the cut was made, small pieces of DNA can be inserted or removed. 
• guide RNA (gRNA), made up of a little, roughly 20-base-long segment of a pre-designed RNA sequence embedded in a larger RNA scaffold. It "guides" Cas9 to the correct region of the genome while the larger scaffold portion binds to DNA.

The purpose of the gRNA is to locate and attach itself to a particular DNA sequence, hence it should be carefully designed. The RNA bases in the gRNA complement the target DNA sequence. Once the gRNA binds to its target DNA, Cas9 moves to that location and cuts both strands of the DNA. After the cut, the cell detects the break and attempts to fix the damage by activating its natural DNA repair system. Scientists can then take advantage of this repair system to alter one or more genes in the genome of the cell of interest. The creation of the site-specific genome-editing tool CRISPR and the protein Cas9 that goes along with it is transforming genetic engineering thanks to its incredibly powerful mechanism, which may lead to successful pest management.

By employing CRISPR/Cas9-based gene editing, knowledge of genes involved in growth, development, and reproduction has increased, leading to breakthroughs in understanding pesticide mechanisms.

Among the genes explored by Asad et al. (2025) are:

• PxSer2, part of the serine protease family, is essential in insect seminal fluid. Mutation of this gene causes dominant male sterility that can be inherited.
• PxCry1, vital for maintaining the moth’s internal clock, causes loss of normal day-night movement patterns when absent. The moth can no longer adjust its rhythm, even in darkness.
• PxGSS1 produces an enzyme blocking toxic compounds from cruciferous plants. Its knockout reduces pest host adaptation.

CRISPR/Cas9 is also used to control pest populations through gene drives and sex separation using markers. Gene drives bypass Mendelian inheritance, allowing inserted genes to spread rapidly. Enzmann (2018) noted their potential to reduce pest populations or spread advantageous genes in wild species.

Sex separation in P. xylostella is achieved through gene knock-in, inserting Cas9-CFP (cyan fluorescent protein) into the Z chromosome, enabling researchers to visually distinguish males and females by color. As Asad et al. (2025) stated, this technique supports sterile insect management.

To improve genome editing in P. xylostella, future studies should concentrate on improving germline transmission, optimizing HDR-mediated repair, and investigating different CRISPR variants such CRISPR/Cas12 and CRISPR/Cas13. Moreover, the sustainability and long-term effectiveness of CRISPR-based tactics will be improved by combining them with ecological techniques like biological control and integrated pest management (IPM). Asad et al., 2025 noted that the entire potential of CRISPR/Cas9 in pest management can be realized through these initiatives, resulting in more long-lasting and efficient diamondback moth control methods.