in yeast by using genes of five different plants (Moses et al. 2014). In contrast to
microbes requiring fermentable sugars from plant-derived lignocellulose as an
energy source, utilizing photosynthetic hosts is better. Plants synthesize the desired
metabolites using renewable resources (Kim et al. 2013; Sanchez and Karhumaa
2015), allow the post-translational modifications necessary for accurate protein
folding and enzyme functionality (Ikram et al. 2015) and avoid the need for
metabolite purification as the desired metabolites can be directly consumed via
food or feed crops. Hsu et al. (2014) suggested that targeted knockout of genes is
extremely needed in SynBio programmes when challenging side branches of metabolic pathways or negative feedback loops are to be silenced or removed. Sterol side
chain reductase 2 (SSR2) was knocked out using TALENs to reduce cholesterol and
steroidal glycoalkaloids levels in tetraploid potatoes (Sawai et al. 2014). The ability
of homologous recombination in mosses such as P. patens (Schaefer and Zryd 1997)
offers an advantage to mosses as chassis over vascular plant hosts. Another considerable host can be algae and cyanobacteria, which are cultivated in water or nutrientladen agricultural wastewater, thus avoiding exhaustion of arable land for their
cultivation (Dismukes et al. 2008). Furthermore, this can lead to the consumption
of concentrated aquatic CO 2 derived from industrial emissions (Nozzi et al. 2013;
Arendt et al. 2016). Crocetin, naturally existing in Crocus sativus L., has potent
applications in medical and food fields because of antitumor, antioxidation,
antihypertension, antiatherosclerotic and antidepressant activities. To promote
crocetin production in a heterologous host, key enzymes like β-carotene hydroxylase
(CrtZ), carotenoid cleavage dioxygenase (CCD) and aldehyde dehydrogenase
(ALD) have to be engineered combinatorially. Chai et al. (2017) proposed superior
crocetin production by combinatorial manipulation of CrtZ, CCD and ALD and
regulating protein expression level in S. cerevisiae (Chai et al. 2017).
Thus it is likely that agricultural traditions could shift from extensive cultivation
of crops for a single product, to the cultivation of feedstock crops to supply carbon
source for microbial growth, which promises to engender a wider variety of synthetic
natural commodities, even in unbefitting season. These innovative alterations in
agriculture can lead to better water use efficiencies and improvement in the resilience
and productivity of agriculture (Goold et al. 2018).
15.9 Synthetic Plant Genomes
Deployment of de novo genomes into plants is still one of the far-reaching objectives
of SynBio. Ground-breaking efforts in the bacterial cell construction having a
synthesized Mycoplasma genome (Gibson et al. 2010) and the de novo creation of
synthetic chromosomes in yeast (Dymond et al. 2011 have pointed out few
principles for SynBio aspirants to follow. Firstly, the synthetic genomes should
have approximately wild-type phenotypes and fitness; secondly, it should not
include tRNA genes and transposons; and lastly, there should be genome editing
sites for upcoming researches (Dymond et al. 2011). A streamlined synthetic
genome: the Plastome (prokaryotic in nature) can be used as a vector for building
472
P. Singla
microbes requiring fermentable sugars from plant-derived lignocellulose as an
energy source, utilizing photosynthetic hosts is better. Plants synthesize the desired
metabolites using renewable resources (Kim et al. 2013; Sanchez and Karhumaa
2015), allow the post-translational modifications necessary for accurate protein
folding and enzyme functionality (Ikram et al. 2015) and avoid the need for
metabolite purification as the desired metabolites can be directly consumed via
food or feed crops. Hsu et al. (2014) suggested that targeted knockout of genes is
extremely needed in SynBio programmes when challenging side branches of metabolic pathways or negative feedback loops are to be silenced or removed. Sterol side
chain reductase 2 (SSR2) was knocked out using TALENs to reduce cholesterol and
steroidal glycoalkaloids levels in tetraploid potatoes (Sawai et al. 2014). The ability
of homologous recombination in mosses such as P. patens (Schaefer and Zryd 1997)
offers an advantage to mosses as chassis over vascular plant hosts. Another considerable host can be algae and cyanobacteria, which are cultivated in water or nutrientladen agricultural wastewater, thus avoiding exhaustion of arable land for their
cultivation (Dismukes et al. 2008). Furthermore, this can lead to the consumption
of concentrated aquatic CO 2 derived from industrial emissions (Nozzi et al. 2013;
Arendt et al. 2016). Crocetin, naturally existing in Crocus sativus L., has potent
applications in medical and food fields because of antitumor, antioxidation,
antihypertension, antiatherosclerotic and antidepressant activities. To promote
crocetin production in a heterologous host, key enzymes like β-carotene hydroxylase
(CrtZ), carotenoid cleavage dioxygenase (CCD) and aldehyde dehydrogenase
(ALD) have to be engineered combinatorially. Chai et al. (2017) proposed superior
crocetin production by combinatorial manipulation of CrtZ, CCD and ALD and
regulating protein expression level in S. cerevisiae (Chai et al. 2017).
Thus it is likely that agricultural traditions could shift from extensive cultivation
of crops for a single product, to the cultivation of feedstock crops to supply carbon
source for microbial growth, which promises to engender a wider variety of synthetic
natural commodities, even in unbefitting season. These innovative alterations in
agriculture can lead to better water use efficiencies and improvement in the resilience
and productivity of agriculture (Goold et al. 2018).
15.9 Synthetic Plant Genomes
Deployment of de novo genomes into plants is still one of the far-reaching objectives
of SynBio. Ground-breaking efforts in the bacterial cell construction having a
synthesized Mycoplasma genome (Gibson et al. 2010) and the de novo creation of
synthetic chromosomes in yeast (Dymond et al. 2011 have pointed out few
principles for SynBio aspirants to follow. Firstly, the synthetic genomes should
have approximately wild-type phenotypes and fitness; secondly, it should not
include tRNA genes and transposons; and lastly, there should be genome editing
sites for upcoming researches (Dymond et al. 2011). A streamlined synthetic
genome: the Plastome (prokaryotic in nature) can be used as a vector for building
472
P. Singla