Concept of Plant Genetic Engineering towards Food Security in Africa

Modern biotechnology tools are paramount for improved and sustainable agriculture aimed at achieving food security in Africa. The continent is continually faced with the challenge of providing for its increasingly growing population amongst rapidly diminishing resources and inevitable interferences of environmental biotic and abiotic factors. It is therefore pertinent to leverage on technologies that have aided developed countries of the world to attain self-reliance. Efforts to create positive public opinion and thus alleviate fear associated with biotechnology products and GM crops require a comprehensive understanding of the concept of plant genetic engineering. This review highlights the basic concept of genetic engineering and measures taken to ensure its safety to life and the environment.


Introduction
problems (Kumar, 2012). G e n e t i c e n g i n e e r i n g a n d t h e Agricultural productivity in terms of crop development of genetically modified organisms yield and quality in the past twenty years has (GMO) particularly for the purposes of food and been enhanced by modern agricultural practices feed have been the most controversial topic in and conventional breeding such as introduction the past decades (Zhang et al., 2016). Safety of new varieties into localities with no preconcerns have been centered on unknown long-existence, selection of varieties with desirable term impact on human and animal health as well characteristics for further cultivation and as the environment (Buiatti et al., 2013).
hybridization of two parents with desirable However, the application of GMO technologies characteristics to produce hybrid with improved has recorded great achievements in the fields of traits (Barampuram and Zhang, 2011). Despite agriculture (Thomson et al., 2010), medicine these achievements, demands on agricultural (Diaz & Fridovich-Keil, 2016) and industry productivity continue to increase due to (Moschini, 2006). Some of these applications population growth, environmental deterioration, include genetically modified plants and animal accelerated emergence of new crop and with improved agronomical and nutritional traits livestock diseases, continuous variation in and for use as bioreactors for the production of climatic conditions and incessant need for enzymes and chemicals in industry. Life-saving sustainable energy. Unfortunately, the length of drugs such as insulin and other human proteins time required in bringing new improved varieties have long been produced using genetically to farmers by traditional breeding pose as a modified microorganisms (Diaz & Fridovich-Keil, deterrent to immediately proffering solutions to 2016), as well as biodegradable plastics and circumvent the effects of famine, hunger and biosensors towards tackling environmental poverty particularly in the developing worlds (Mlambo et al., 2001 (James, 2011;Ruane, 2013). and animals as well as the increasing scourge of Apart from crop improvement, genetically climate change demands that Africa promptly modified plants potentially provide a variety of reconsiders and repositions her stand towards other benefits; such as improving the health the acceptance, commercialization and adoption status of populations by consumption of of GM crops. This review highlights the basic nutritionally enhanced foods such as Golden Rice concept of genetic engineering and measures modified for elevated levels of beta-carotene, a taken to ensure its safety to life and the precursor for Vitamin A (Unnevehr et al., 2007), environment. and by the production of cost effective and easyto-manage oral vaccines derived from plants Impact of Plant Genetic Engineering genetically modified to express such proteins. Genetic engineering is the construction GM crops can also be applied to promote organic of recombinant DNA molecules coding for a farming through the reduction of inputs of desired trait and the subsequent integration and agrochemicals into the environment or designed expression of this DNA in plants, animals or for bioremediation of soils contaminated with microorganisms with the intent to modify the heavy metals and toxic organic compounds characteristics of the target organism (Kumar, (Macek et al., 2008;Brookes and Barfoot, 2012). 2012). Organisms produced in this manner are referred to as genetically modified organism Tools required for plant genetic engineering (GMO). Importantly, the genes of interest (GOI) Certain tools are required for carrying out transferred in this manner may not necessarily genetic transformation of an organism. Firstly, a be from the same or other species, but can be genetic construct must be produced for carrying sourced from completely unrelated organisms. the genetic material intended for integration into They are thus referred to as "transgenes" (Qaim, the target genome. This consists of the gene(s) 2009) and the resulting modified organisms as of interest conferring the desired novel trait(s), a being "transgenic".
promoter that drives expression of the gene of Genetically modified crops have been interest in the desired manner, and a DNA poly-A used commercially for more than twenty years sequence that signals the end of the desired and contributed to significant impact on the gene expression. Fused together, these economy and general well-being of farmers and components are referred to as the gene consumers, particularly in North America expression cassette. A DNA transfer method is (Adenle, 2011). GM crops are presently grown in then required to introduce the expression cassette and ensure its integration into the Visual marker genes employed in plant genome of the target organism. Because gene genetic transformation systems to date include transfer and integration is a relatively inefficient â-glucuronidase (GUS), , firefly luciferase (LUC) , process (usually only 1% or less of the treated green fluorescent protein (GFP) and red cells are successfully transformed), a selectable fluorescent protein (Okwuonu et al., 2015). marker is required to facilitate recovery of the Fluorescent proteins are mostly preferred as successful transformation events from among their detection and monitoring are nonthe non-transgenic cells. The ability to monitor destructive, allowing continuous monitoring of the transformation process is important in the same putative transgenic cells and tissues understanding the progress and pattern of over time and across developmental process at transgene expression. This makes scorable or both the tissue culture and whole plant stages . visual markers essential tools for development Genetic transformation methods and application of genetic transformation technologies for a given organism. Finally, a There are basically two DNA transfer methods target tissue is required into which the new DNA employed in the production of transgenic plants; can be effectively integrated. If a whole new referred to as indirect and direct DNA transfer transgenic organism such as a plant is to be processes (Narusaka et al., 2012). Indirect DNA recovered, then the target tissue should be transfer involves the use of bacteria such as totipotent in nature, being both amenable to Agrobacterium tumefaciens or Agrobacterium receiving the foreign DNA, and after the selection rhizogenes to transfer foreign DNA into plant process, to regenerate into a whole organism cells, while direct DNA transfer utilizes physical expressing the novel trait.
or chemical methods of transferring foreign Target tissues employed to date include genes into the plant cell. Direct DNA transfer organogenic callus, embryogenic callus, apical methods include particle bombardment, shoots, axillary buds, embryogenic leaflets, electroporation, polyethylene glycol, siliconflowers, immature embryos and in vitro shoots carbide whiskers and liposome-mediated (Barampuram and Zhang, 2011). Both transformation techniques. transformation efficiency and regeneration of transgenic events from these target materials Agrobacterium-mediated transformation entails depends on the plant type, method of DNA the use of non-virulent strains of A. tumefaciens transfer and amenability of these tissues to or A. rhizogenes to mediate the transfer of tissue culture processes.
foreign DNA through the cell wall and into the Selectable marker genes used for nucleus. In their virulent forms these bacteria selection of putative transgenic events include are the causative agents of "crown gall disease" geneticin (Li et al., 1996)  genes responsible for producing the disease Promoters are usually placed directly conditions. The T-DNA element is flanked by two upstream of a gene coding region and contain 25-bp direct repeats called the left border (LB) specific sequences that are recognized by and right border (RB), respectively, which act as regulatory proteins involved in the initiation of the signal for initiation and termination of the Ttranscription (Peremarti et al., 2010). These DNA transfer process (Zupan et al., 2000). The could be constitutive, inducible, tissue specific tumor and root inducing genes have been and developmental stage specific promoters.  (Li et al., 2012; reaction and then is treated with specific primers Putcha and Fauser, 2013).
to show gene expression.

Transgenic Analysis Phenotypic Analysis Putative transgenic events are subjected
Phenotypes of the recovered events are to batteries of molecular analysis to ascertain the also considered with those with unexpected integration of the desired gene, copy number of phenotypes eliminated from the pipeline. Events gene inserted, level of gene expression and with low copy number (1-2) gene copy, high types of protein produced, including allergens expression of transgene with no detectable (Taylor et al., 2012). The presence of the variation in phenotype are further evaluated for transgene in the target genome is easily the desired trait and phenotypic impact of the determined by means of polymerase chain transgene in the greenhouse under much reaction (PCR) using gene specific primers while regulated environmental conditions such as light copy number of genes inserted is determined by intensity, temperature, humidity and nucleic acid hybridization methods such as Dot photoperiod. blot and Southern blot analysis using specific Events showing high expression of the probes produced with sequences of the targeted desired trait with no variation in phenotype are gene. Gene expression levels can be determined further advanced to confined field trial (CFT) to by Northern blot analysis or reverse ascertain performance in the open field as well as transcriptase polymerase chain reaction (RTits impact in the environment. Such events are PCR) while protein expression is determined by evaluated in a confined field site, excluded from Western blot analysis.
fields bearing same type of crop to prevent gene Intact genomic DNA extracted from flow. Animal and unauthorized persons are also tissues of recovered transgenic lines such as barred from entering the site in other to ensure leaves, roots, shoots and stem are used in PCR, strict compliance to regulatory requirement. Dot blot and Southern blot analysis. Various PCR kits containing master mixes of enzymes and Biosafety policies and Regulations buffers are readily available in the market and In order to ensure personal, public and are reacted with genomic DNA derived from environmental safety in the handling and release plant samples in the presence of gene specific of GM crops, biosafety laws and regulatory primers. The reaction mixture is set up in agencies enforcing these laws are mandatory in thermocycler at conditions determined countries intending to engage in transgenic empirically for the amplification of the target research and the production of GM crops. This gene. For transgene integration and copy entails adherence to containment principles, number detection, genomic DNA derived from practices and technologies in preventing plant samples are separated by gel unintentional exposure and release of pathogen, electrophoresis and embedded in nitrocellulose toxins, genetic materials, hazardous chemicals paper which is then treated with gene specific and radiation to the environment (Kumar, 2012). probe. Hybridization of probe with DNA This fundamentally involves the enactment of sequence confirms integration while the number Biosafety laws by individual countries in line with of bands observed shows the number of gene the Codex guidelines and institutionalization of copies integrated.
governing agencies that will implement these High quality RNA and protein samples laws. Mostly, awareness creation among extracted from recovered transgenic plants are researchers and the public to biological safety at used for detection of gene and protein the grass root is paramount (Kumar, 2012). expression levels, respectively. The RNA and Biosafety requirement for transgenic p r o t e i n m o l e c u l e s s e p a ra t e d b y g e l research in most countries requires the electrophoresis are embedded on nitrocellulose accreditation of institutions by the Biosafety paper and treated with specific probes in Management Agencies. Institutions involved in Northern and Western blot nucleic acid dealing with GMO are expected to have in place hybridization assay while for RT-PCR, the RNA is well contained laboratories with trained reversed back to DNA in reverse transcriptase personnel and limited access to unauthorized  https://www.britannica.com/science/genetically -modified-organism/GMOs-in-medicine-andresearch