Understanding the Science of Gene Drive and the Potential for an Improved Crop Pest Control System in Nigeria
Abraham Isah Rose S.M. Gidado
May 2019
Figure 1: Schematic representation of the gene drive technology
Source: https://www.nytimes.com/2015/12/22/science/gene-drives-offer-new-hope-against-diseases-and-crop-pests.html
The control of pest species (herbivorous and disease‐vectoring insects, pathogens and weeds) in the Nigerian agricultural system have become dominated by the application of synthetic pesticides which have often resulted to environmental pollution that has greatly contributed to climate change with lethal consequences like increased pest attack, decreased crop yield and extreme heat stress in plants. Though in the past, the chemical method of insect pest control has been significantly applied to reduce crop yield losses through enhanced control of insect vectors of plant diseases, increasing concerns about the off‐target environmental and human health impacts of pesticide use coupled with the widespread evolution of pesticide resistance calls for urgent novel alternative control strategies.
Various conventional insect pest control and population suppression measures such as the physical, agronomic, biological and agro‐ecological methods are limited in genetic control strategies that directly manipulate the genomes of pest species to reduce their fitness. Advances in genetic technology have made it possible to alter the genes and consequentially the phenotypes of plants, microbes, fungi and animals. A typical example of the potential for human‐mediated, genetic interventions to aid in the suppression and control of plant diseases causing insect pest is the application of gene drive technology.
Figure 2: Molecular Mechanism of Gene Drive
Source: https://en.wikipedia.org/wiki/Gene_drive#/media/File:Molecular_mechanism_of_gene_drive.svg
Gene drives are systems that warrant biased inheritance by improving the possibility of DNA sequence passing from one generation to the other via sexual reproduction and potentially throughout an entire population. It is a modern biotechnology technique that alters the tendency of transmitting a specific allele from the natural 50% probability by propagating a particular set of genes throughout a population. In agriculture, gene drive has been recently applied to control invasive species or eliminate herbicide and pesticide resistance. The application of gene drive in the Nigeria’s agricultural system can greatly help in the control of deadly insect pests that cause damages to crops and consequentially reduction in food production without the need for insecticides application.
The gene drive element is made up of the Cas9 nuclease, guide RNA and an edited repair template for the integration of a new gene at the cut site. The CRISPR–Cas9 gene drive system works at the molecular level by cutting the wild type form of a gene and promoting the repair of the cell by copying the homologous form of the gene which contains the gene drive to the damaged version. This results in the transformation of the heterozygote carriers of a gene drive into homozygotes that is eventually passed on to all progenies. The cycle of transformation of the progenies into homozygotes keeps on occurring until the gene drive spreads throughout the population.
In agriculture, the application of CRISPR–Cas9 gene drive to weed control have been validated very useful and efficient. Population suppression of weed species suing the CRISPR-Cas9 gene drive is based on the introduction and spread of fitness load that can limit the dispersal and abundance of weed populations.
Figure 3: Control of the agricultural weed using the CRISPR–Cas9 gene drive system. Plants are capable of carrying out the gene drive system in a heterogenous state at the cellular level after an effective mating between the introduced and wild‐type individuals (a). The Cas9 nuclease will be directed by the RNA guide to excise the DNA at the recognition site on the wildtype chromosome (b). The homologous recombination uses the drive chromosome as a template to repair the cut and convert the individual to a homozygous state for the drive (c) At the population level, there is the introduction of the individuals with the engineered drive (blue plants) into a wild population (green plants) (d) the drive allele spreads through the population over time (e, f) until individuals carrying the drive allele are more than the wild population. This whole process is called “super-Mendelian” inheritance.
Source: Godfray et al. (2017) and Frey and Malik (2017).
What if Nigeria uses Gene drive to revamp her food crop industry? The plant sucking insects in the order Hemiptera is one of the most devastating insects in the Nigeria’s farm. The negative effects of these destructive crop pest results from the stress and damage caused by feeding in addition to the plant pathogens they transmit while probing plant tissue. The vector of the bacterium Candidatus Liberibacter asiaticus which causes citrus greening disease, Diaphorina citri, Nilaparvata lugens, a notorious pest of rice that has the ability to transmit viruses and Bemisia tabaci, a species of whitefly known to feed on over 500 host plants all belong to the order Hemiptera. These devastating insect pests have been known to reduce the crop yield of Nigerian farmers by more than 50%. Insect pests population suppression using Cas9-mediated gene drive technology can provide a cost-effective, accurate and simple method for control. Several studies have shown that the Cas9-mediated gene drive technology is cheaper and will be easily affordable by the efficient Nigerian scientists to explore. The application of the gene drive technologies have many more controls over several other devastating insects in Nigeria and may be very necessary to adopt it to rescue our ailing food crop industry from the attack by destructive insect pest of crops.
In conclusion, the gene drive‐based pest control strategy is attracting great interest from farmers all over the world and should receive more attention from the Nigerian policymakers and the public given it enormous potential impacts on the environment. Nigerian farmers need to embrace the application of gene drive technology to their seeds and food crops in order to achieve food security that will translate to national development.
A publication of Open Forum on Agricultural Biotechnology (OFAB) in Africa
c/o National Biotechnology Development Agency (NABDA),
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