Genetic Engineering for Oil Modification

*Muthulakshmi Chellamuthu, Kokiladevi Eswaran and Selvi Subramanian*

#### **Abstract**

Genetic manipulation is a strong tool for modifying crops to produce a considerably wider range of valuable products which gratifies human health benefits and industrial needs. Oilseed crops can be modified both for improving the existing lipid products and engineering novel lipid products. Global demand for vegetable oils is rising as a result of rising per capita consumption of oil in our dietary habits and its use in biofuels. There are numerous potential markets for renewable, carbon-neutral, 'eco-friendly' oil-based compounds produced by crops as substitutes for non-renewable petroleum products. Existing oil crops, on the other hand, have limited fatty acid compositions, making them unsuitable for use as industrial feedstocks. As a result, increasing oil output is necessary to fulfill rising demand. Increasing the oil content of oilseed crops is one way to increase oil yield without expanding the area under cultivation. Besides, the pharmaceutical and nutraceutical values of oilseed crops are being improved by genetic engineering techniques. This chapter addresses the current state of the art gene manipulation strategies followed in oilseed crops for oil modification to fulfill the growing human needs.

**Keywords:** oil quality, yield, essential fatty acids

#### **1. Introduction**

During India's green revolution in the mid-twentieth century, the use of agrochemicals and high-yielding crop types established through traditional plant breeding procedures resulted in a major increase in crop productivity [1]. Conventional plant breeding can no longer meet the ever-increasing global food demand. Food insecurity and malnutrition are two of the most major threats to human health today, claiming the lives of millions of people in poor countries. To stay healthy, we need to eat a range of meals that contain all of the needed nutrients, as well as those that provide health advantages beyond basic nutrition [2]. It is now way to encourage sustainable farming approaches for increasing crop output while preserving all natural resource to the greatest extent possible [3]. Agricultural biotechnology is proven to be a valuable addition to traditional ways for addressing the global need for high-quality food. We now have access to large gene pools that may be utilized to confer desirable characteristics in economically significant crops thanks to modern plant biotechnology technologies. Crop

varieties that are genetically modified (GM) can help us satisfy the demand for high-yielding, nutritionally balanced, biotic and abiotic stress tolerant crops [4]. Oilseed crop adoption has increased significantly in recent decades as a result of high demand for human consumption and industry interest. The composition of the seed oils, which are composed of a broad group of fatty acids with six predominant types and other unusual fatty acids produced by wild plant species with chain lengths ranging from 8 to 24 carbons, such as 16 or 18 carbon palmitic, stearic, oleic, linoleic, and linolenic acids, and 12 carbon lauric acid. In this study, a review of the major advances in genetic improvement of oilseed crops is provided, beginning with omics to understand metabolic routes and identify key genes in seed oil production and progression to use modern biotechnology. Genetic engineering is a new breeding technique (NBT) that has enabled the functional study of genes with potential applications. The important advancements in plant genetic improvement using current biotechnology, with an emphasis on oilseed crops such as *Sesamum indicum*, *Arachis hypogaea*, *Carthamus tinctorius* and *Jatropha curcas* are discussed in the following sections.

#### **2. Genetic modified crops vs conventional breeding**

In several countries, GM crops created by adding genes for greater agronomic performance and/or enhanced nutrition are commercially grown. The source of the DNA utilized to develop the GM crop has a significant impact on the rigor of the food safety assessment. If the DNA comes from an edible plant, the regulatory process prior to commercialization will be streamlined, and customer acceptance will improve [5]. Crops that have been traditionally bred and those that have been genetically modified through various methods of gene transfer technologies are the results of genetic changes. Both conventional breeding and GM technologies have the potential to alter an organism's genetic makeup in terms of DNA sequences and gene order. However, compared to traditional breeding, where thousands of uncharacterized genes of an organism may be involved, the quantity of genetic modifications brought about by GM technology is limited and clearly documented. Furthermore, GM crops are the result of very specific and targeted gene modifications, with well-defined end products like as proteins, metabolites, and phenotypes [6].

#### **3.** *Sesamum indicum*

The genus of *Sesamum* belongs to the clade eudicots; order Lamiales and Pedaliaceae family and broadly grown species around the world [7]. The genus *Sesamum* contains 36 species including 22 species from African continent, seven is found commonly in Asia and Africa, five in Asia and one species in Brazil and Greek island. Most of the wild species of *Sesamum* originated in the African continent however the crop has been domesticated from its wild relative species *S. malabaricum* native to south Asia [8]. Sesame harbors a vast range of diversity and adaptation to various environments and it was recorded with long-term natural and artificial selections [9]. The percentage content of other fatty acids like oleic acid, linoleic acid, palmitic acid, erudic acid are 36%, 30%, 9%, 0.8% respectively. These are the major fatty acids present in sesame. Linolenic acid (omega 3 fatty acid) content is in very trace amounts in sesame seeds. The percentage content of poly unsaturated fatty acids ranges from 30.9 to 52.5%, it shows very large variation in their germplasm (**Figure 1**) [10].

*Genetic Engineering for Oil Modification DOI: http://dx.doi.org/10.5772/intechopen.101823*

#### **Figure 1.**

*Future directions and strategies for enhancing sesame oil yield and improvement.*

### **4. Nutritional value of sesame**

Sesame not only contains protein, carbohydrates, poly unsaturated fatty acids, it also contains the lignans, phytosterols, phytates and tocopherols. They keep on maintaining the oil quality level in long shelf life time by preventing the oxidative rancidity [11]. The combination of these compounds is mainly responsible for the good oxidative stability of the sesame seed oil [12]. The antioxidant property of the oil aids in preventing the degenerative diseases like cancer, cardiovascular disease, atherosclerosis and the process of aging [13].

The major desmethylsterols present in sesame seed oil are β-sitosterol, campasterol, stigma sterol, Δ-5 and avenasterol [14]. Sesame oil also contain some enzymes such as Protex 7 L, Alcalase 2.4 L, Viscozyme L, Natuzyme and kemzyme. Among those enzymes Alcalase is found in large amounts in sesame [15]. These enzymes are mainly used for aqueous oil extraction process which is an alternative for solvent extraction. An Enzyme-assisted aqueous extraction (EAAE) process which is used to recover the high-quality protein for human consumption [16].

#### **5. Sesame breeding**

Plant breeding allows the successful management of existing genetic diversity as well as the development of new ones in order to achieve desired traits. There

is different type of breeding approaches which is employed for genetic improvement of sesame varying from plant selection, hybrid development and molecular breeding. In conventional breeding the choice of parental lines and development of sesame types with desired characters is attained through pedigree selection from segregating generations [17]. Plant selection is vital for increasing seed yield and development of novel sesame varieties [18]. Several phenotypic traits are useful for determining selection criteria such as number of capsules, branching, biomass, harvest index which reveals positive correlation with sesame seed yield [19]. Hybridization is one of the frequently used techniques in conventional breeding technique. Combination of desired traits with different plant lines can be achieved through cross-pollination. Cytoplasmic male sterility lines in sesame were developed by hybridizing *S. indicum* with its wild relative *S. malabaricum*. Many hybrids exhibited high heterosis for oil content, seed yield and number of capsules per plant [20]. Mutation breeding involves induction of new genetic variability through spontaneous or artificial mutagens either chemical or physical. Sesame mutants have been developed for desirable traits for quality, seed color, higher yield, plant architecture and larger seed size [21]. The gamma ray induced mutants were developed with improved plant growth having determinate growth habit, resistance to *Fusarium* blight, improved oil quality with higher oleic acid and low linoleic acid content [22].

### **6. Genetic improvement of sesame**

Sesame breeding uses a variety of novel ways, including genetic engineering, to overcome the disadvantages of traditional breeding. Sesame's resistance to current biotechnology makes it difficult to use. Furthermore, various researchers have tried a variety of ways and media to create callus tissue [23]. Cotyledons, root, hypocotyl segments and sub apical hypocotyl of seedlings were all successful in somatic embryogenesis [24]. In addition, the efficient micro propagation mechanism for sesame conservation and multiplication has been upgraded. This is useful for genetic transformation, reproductive growth, and other tissue culture research. The genetic transformation of sesame by Agrobacterium has been reported, however the transformation frequency is low. High-frequency sesame transformation techniques recently yielded high regeneration and transformation frequency of 57.33% and 42.66%, respectively, for sesame [25–28]. Current crop breeding approaches will not be sufficient to meet the ever-increasing population's demands for food security and nutrition. To speed agricultural genetic improvement, 5G breeding tactics such as genome assembly, germplasm characterization, gene function identification, genomic breeding methodologies, and gene editing technologies have been proposed [29]. Genomic tools and methodologies for phenotype discovery and molecular breeding are provided by genome assembly. A gene expression, proteome, metabolome, and epigenome maps are essential. Researchers from the Chinese Academy of Agricultural Science's Oil Crops Research Institute and other institutions have successfully created a high-quality sesame genome. Two landraces (S. indicum cv. Baizhima and Mishuozhima) and three modern cultivars (S. indicum var. Zhongzhi 13, Yuzhi 11, and Swetha) have genome assembly presently available, providing a significant tool for comparative genomic analysis and gene identification [30]. In seeds of *Nicotiana tabacum*, expression of sesame plastidial FAD7 desaturase modified with endoplasmic reticulum targeting and retention signals increases a-linolenic acid accumulation. The expression of the modified sesame ω-3 desaturase raises the a-linolenic acid concentration in the

#### *Genetic Engineering for Oil Modification DOI: http://dx.doi.org/10.5772/intechopen.101823*

seeds of transgenic tobacco plants by 4.78–6.77%, while lowering the linoleic acid level. The findings suggested that the engineered plastidial ω-3 desaturase from sesame has the potential to influence the profile of a-linolenic acid in tobacco plants by shifting the carbon flux away from linoleic acid, and thus it could be used in a genetic engineering strategy to increase a-linolenic acid levels [31]. Increases in oil content and seed weight were seen when sesame DGAT1 was overexpressed in many lines of *Arabidopsis* thaliana 'Col 0' [32]. Through a genetic engineering technique, the *Fusarium moniliforme* 12/15 bifunctional desaturase gene was used to increase the omega 3 fatty acid content of sesame (Unpublished data). Yeast is a great model for studying lipid production. The oil accumulation and functional characterization of the sesame DGAT and PDAT genes were studied using a yeast H1246 oil synthesis defective mutant [33]. In order to improve the oil quality, another study examined the co-expression of DGAT1 and PDAT1 genes with omega 3 desaturase genes in a yeast expression system (Unpublished data). Sesame transformation research using Agrobacterium to assess the biodiesel potential of transgenic sesame plants showed an increased TAG content by 10% when PDAT1 and FAD3 were combined in a transgenic construct [34].
