## 3 Transgenic Plants--Brief History and Potential Industrial Use  
Transgenic plants are desirable to industry. Although the first organisms to be genetically modified were bacteria, their potential commercial value was quite limited and were of interest only as an initial model [27; 28]. However, the development of transgenic plants promised a completely different scale of production. Commercial interest in biotechnology grew rapidly from the late 1970s to the early 1980s [29]. In 2019, 190.4 million hectares of biotech crops were planted by 17 million farmers in 29 countries, an increase of more than 100-fold since the initial planting of 1.7 million hectares in 1996 [30]. As such, biotech crops are considered to be the most rapidly adopted culture technology in the history of modern agriculture. As of 2019, the United States is home to the largest area of genetically-modified crops worldwide at 71.5 million hectares, followed by Brazil with a little over 52.8 million hectares [31]. The most commonly-grown biotech crops in 2019 were soybeans, corn, cotton, and canola [32]. While there was a 4% reduction in biotech soybean planting, the high adoption rate of 48% of the world's biotech crops, or 91.9 million hectares, was maintained [31]. This acreage accounted for 74% of the total soybean production in the world in 2019 [33]. Generally, transgenic plants are defined as those whose DNA is modified by genetic engineering techniques. Although they were arguably first implemented 10,000 years ago in Southwest Asia, where humans first grew plants through artificial selection and selective cultures [34; 35], the first modern transgenic plants were developed in the early 1980s in an experiment where bacteria and yeast genes were cloned into the Ti plasmid and then used to create a plant containing those new sequences [36]. The results of the experiment and the transgenic plant were published in April 1983 [37]. Transgenic plants contain an artificially inserted gene or genes. These sequences are known as transgenes; they may originate from an unrelated plant or from an entirely different species. The purpose of introducing a combination of genes into a plant is to make it as useful and productive as possible, or for the addition of completely new features [38; 39]. The development of molecular plant breeding has resulted in technological advances in transformation methods, gene expression regulation, protein sorting and accumulation, and the use of various crops as production platforms [40]. One of the most important factors in the plant genetic transformation procedure is the type of explant. For example, the use of different sources of plant cells or tissues (e.g., seeds,  
Figure 1: PRISMA flow diagram demonstrating screening method for article [26]. roots, shoots, leaves, and shoot or root apical meristens) results in different degrees of callus induction, and hence different levels of plant regeneration and genetic transformation efficiency [41; 42]. Many plants (such as soybean, corn, wheat, tomato, rice, etc.) have been genetically modified to achieve higher yields, stress tolerance, and enhanced production of high-value compounds such as recombinant proteins, antibodies, enzymes, and vaccines. This makes them a promising alternative to conventional bioproduction systems, such as bacteria, yeast, and cultured insect and animal cells [43]. An example of such a positive modification was the nutritionally valuable \"golden rice\" and \"golden bananas\", which had elevated levels of \(\beta\)-carotene--a precursor of vitamin A [27; 44; 45]. Another example is tomato fruit producing squalene, phytosterols, \(\alpha\)-tocopherol, and carotenoids [46]. One of the best plant-based alternatives for the production of recombinant proteins are plant-cell suspensions; this is a robust system involving a simple purification procedure and easy downstream processing [47]. In turn, the transformed roots formed by infection with \(R\).