beta-carotene (i.e. provitamin A) concentration (Diretto et al. 2007). Expression of
the two Antirrhinum majus transgenes Delila (Del) and Rosea1 (Ros1) genes in
tomato fruit enhanced the hydrophilic antioxidant capacity of tomato fruit and the
fruits accumulated substantially higher levels of anthocyanins (approximately at par
with the concentration found in blackberries and blueberries). These engineered
tomatoes could substantially add to the hydrophilic antioxidant content in meals and
might substitute antioxidant supplements, such as NAC or vitamins (Butelli et al.
2008). Majer et al. (2017) used Tobacco etch virus vector to express an entire
heterologous metabolic pathway (consisting of three enzymes from the soil bacteria
Pantoea ananatis) to synthesise health-promoting carotenoid lycopene in tobacco
tissues in a cost-effective and scalable manner. In this study, phytoene synthase
(crtB) not only activated the build up of endogenous carotenoids but also acted as an
exceptional wide-spectrum yellow visual indicator (by impacting chloroplast metabolism) for tracking viral infection.
Very-long-chain polyunsaturated fatty acids (VLC-PUFAs) such as arachidonic
acid, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are beneficial
for human brain development and cardiovascular functioning. Since VLC-PUFAs
are abundantly present in microalgae and hardly ever in plants, the only
non-sustainable source is marine fish consuming microalgae. In the earliest
demonstrations of Omega-3 long-chain polyunsaturated fatty acids (LC-PUFA)
engineering, Petrie et al. (2012) introduced a transgenic pathway to increase the
C18 Alpha-linolenic acid (ALA) which was then converted to DHA by a microalgal
D6-desaturase pathway in Arabidopsis thaliana seed oil. Later Petrie et al. (2014)
described the fabrication of fish oil-like levels of omega-3 LC-PUFA EPA and DHA
in Camelia sativa by the introduction of a transgenic D6-desaturase pathway by
utilising yeast and microalgal genes. Later, the introduction of VLC-PUFA biosynthetic genes from moss species (known to accumulate in higher levels), has increased
their concentration in model plants like Camelina sativa (Ruiz-Lopez et al. 2014),
Brassica napus (Napier et al. 2019). These transgenic plants can be future sustainable, terrestrial sources of omega-3 fish oils. Metabolic engineering of customary
seed crops with genes to improve the nutritional excellence of fatty acids can perk up
the qualities of harvested oils. This has been achieved in A. thaliana, using seven
enzymes from five organisms, the yeasts Lanchancea kluyveri, and Pichia pastoris,
and the algae Micromonas pusilla, Pyramimonas cordata and Pavlova salina (Petrie
et al. 2012). This strategy was reused in Camelina sativa, and in both the cases
significant improvement in the nutritional profiles of oils was recorded (Petrie et al.
2014). Synthetic production of one of the world’s most expensive spices saffron can
cut manufacturing costs and ensure a steady supply. At present, a Swiss company is
engineering yeast to harvest the vital flavour and colour compounds of saffron
(Vickers 2016).
Another important facet connected to the nutritional value of food includes the
exclusion of ill-favoured secondary metabolites like cyanogenic glycoside. For
example in cassava (Manihot esculenta Crantz), RNA interference technique aiming
two cytochrome P450 genes—CYP79D1 and CYP79D2, encoding the first
committed enzymes in linamarin and lotaustralin, can block the synthesis of
15 Plant Synthetic Biology: A Paradigm Shift Targeting Stress Mitigation,. . .
467
the two Antirrhinum majus transgenes Delila (Del) and Rosea1 (Ros1) genes in
tomato fruit enhanced the hydrophilic antioxidant capacity of tomato fruit and the
fruits accumulated substantially higher levels of anthocyanins (approximately at par
with the concentration found in blackberries and blueberries). These engineered
tomatoes could substantially add to the hydrophilic antioxidant content in meals and
might substitute antioxidant supplements, such as NAC or vitamins (Butelli et al.
2008). Majer et al. (2017) used Tobacco etch virus vector to express an entire
heterologous metabolic pathway (consisting of three enzymes from the soil bacteria
Pantoea ananatis) to synthesise health-promoting carotenoid lycopene in tobacco
tissues in a cost-effective and scalable manner. In this study, phytoene synthase
(crtB) not only activated the build up of endogenous carotenoids but also acted as an
exceptional wide-spectrum yellow visual indicator (by impacting chloroplast metabolism) for tracking viral infection.
Very-long-chain polyunsaturated fatty acids (VLC-PUFAs) such as arachidonic
acid, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are beneficial
for human brain development and cardiovascular functioning. Since VLC-PUFAs
are abundantly present in microalgae and hardly ever in plants, the only
non-sustainable source is marine fish consuming microalgae. In the earliest
demonstrations of Omega-3 long-chain polyunsaturated fatty acids (LC-PUFA)
engineering, Petrie et al. (2012) introduced a transgenic pathway to increase the
C18 Alpha-linolenic acid (ALA) which was then converted to DHA by a microalgal
D6-desaturase pathway in Arabidopsis thaliana seed oil. Later Petrie et al. (2014)
described the fabrication of fish oil-like levels of omega-3 LC-PUFA EPA and DHA
in Camelia sativa by the introduction of a transgenic D6-desaturase pathway by
utilising yeast and microalgal genes. Later, the introduction of VLC-PUFA biosynthetic genes from moss species (known to accumulate in higher levels), has increased
their concentration in model plants like Camelina sativa (Ruiz-Lopez et al. 2014),
Brassica napus (Napier et al. 2019). These transgenic plants can be future sustainable, terrestrial sources of omega-3 fish oils. Metabolic engineering of customary
seed crops with genes to improve the nutritional excellence of fatty acids can perk up
the qualities of harvested oils. This has been achieved in A. thaliana, using seven
enzymes from five organisms, the yeasts Lanchancea kluyveri, and Pichia pastoris,
and the algae Micromonas pusilla, Pyramimonas cordata and Pavlova salina (Petrie
et al. 2012). This strategy was reused in Camelina sativa, and in both the cases
significant improvement in the nutritional profiles of oils was recorded (Petrie et al.
2014). Synthetic production of one of the world’s most expensive spices saffron can
cut manufacturing costs and ensure a steady supply. At present, a Swiss company is
engineering yeast to harvest the vital flavour and colour compounds of saffron
(Vickers 2016).
Another important facet connected to the nutritional value of food includes the
exclusion of ill-favoured secondary metabolites like cyanogenic glycoside. For
example in cassava (Manihot esculenta Crantz), RNA interference technique aiming
two cytochrome P450 genes—CYP79D1 and CYP79D2, encoding the first
committed enzymes in linamarin and lotaustralin, can block the synthesis of
15 Plant Synthetic Biology: A Paradigm Shift Targeting Stress Mitigation,. . .
467