Fueling the future; plant genetic engineering for sustainable biodiesel production

Biodiesel has huge potentials as a green and technologically feasible alternative to fossil diesel. However, biodiesel production from edible oil crops has been widely criticized while nonedible oil plants are associated with some serious disadvantages, such as high cost, low oil yield, and unsuitable oil composition. The next generation sequencing (NGS), omics technologies, and genetic engineering have opened new paths toward achieving high performance-oil plants varieties for commercial biodiesel production. The intent of the present review paper is to review and critically discuss the recent genetic and metabolic engineering strategies developed to overcome the shortcoming faced in nonedible plants, including Jatropha curcas and Camelina sativa, as emerging platforms for biodiesel production. These strategies have been looked into three different categories. Through the first strategy aimed at enhancing oil content, the key genes involved in triacylglycerols (TAGs) biosynthesis pathway (e.g., diacylglycerol acyltransferase (DGAT), acetyl-CoA carboxylase (ACCase), and glycerol‐3‐phosphate dehydrogenase (GPD1)), genes affecting seed size and plant growth (e.g., transcription factors (WRI1), auxin response factor 19 (ARF19),  leafy cotyledon1 (LEC1), purple acid phosphatase 2 (PAP2), G-protein c subunit 3 (AGG3), and flowering locus T (FT)), as well as genes involved in TAGs degradation (e.g., sugar-dependent protein 1 triacylglycerol lipase (SDP1)) have been deliberated. While through the second strategy targeting enhanced oil composition, suppression of the genes involved in the biosynthesis of linoleic acids (e.g., fatty acid desaturase (FAD2), fatty acid elongase (FAE1), acyl-ACP thioesterase (FATB), and ketoacyl-ACP synthase II (KASII)), suppression of the genes encoding toxic metabolites (curcin precursor and casbene synthase (JcCASA)), and finally, engineering the genes responsible for the production of unusual TAGs (e.g., Acetyl-TAGs and hydroxylated fatty acids (HFA)) have been debated. In addition to those, enhancing tolerance to biotic (pest and disease) and abiotic (drought, salinity, freezing, and heavy metals) stresses as another important genetic engineering strategy to facilitate the cultivation of nonedible oil plants under conditions unsuitable for food crops has been addressed. Finally, the challenges faced prior to successful commercialization of the resultant GM oil plants such have been presented.