Characterization of all enzymes required for 9-THC and CBD biosynthesis, permits
the fabrication of these compounds in heterologous host organisms. Thus, Carvalho
et al. (2017) explored an alternative strategy where microbial production can support
the design of novel cannabinoids with enhanced properties by the incorporation of
tailored enzymes. They suggested that a chassis organism can also be designed for
the scalable biosynthesis of less-abundant cannabinoids whose efficacy as medical
drugs can be further tested. Zirpel et al. (2017) also reconstituted biosynthetic
pathway for THCA production from C. sativa in microbial host—Komagataella
phaffii by combining the bacterial prenyltransferase NphB with the THCA forming
enzyme. The WHO classifies opioids as a significant class of medicines that consist
of medication like analgesic morphine and the antitussive codeine (World Health
Organization 2013). All natural opiates (morphine, codeine) and semi-synthetic
opioids (oxycodone, hydrocodone, hydromorphone) are presently obtained from
the opium poppy (Papaver somniferum). Susceptibility of poppy farming to biotic
factors and increasing market demands are growing pressure on the only resource of
opioids. Even, their industrial synthesis has been reported to be commercially
uncompetitive (Reed and Hudlicky 2015). This challenge related to poppy supply
can be addressed by microbial-based synthesis of opioids or their precursor
benzylisoquinoline alkaloids (BIAs). With SynBio technique, biosynthesis of
BIAs downstream of (S)-reticuline, can be reconstructed in Escherichia coli
(Nakagawa et al. 2011) and yeast (Trenchard et al. 2015) from sustainable carbon
and nitrogen resources. DeLoache et al. (2015) and Trenchard et al. (2015)
engineered the biosynthetic pathway, from tyrosine to (S)-reticuline, (Thodey et al.
2014) engineered the pathway from thebaine to morphine and (Fossati et al. 2015)
from (R)-reticuline to codeine. However, it is difficult to design fully functional
entire biosynthetic pathway of 20 heterologous genes essential for their absolute
synthesis. Galanie et al. (2015) engineered yeast with 21 (thebaine) and
23 (hydrocodone) enzyme activities from plants, mammals, bacteria and yeast itself,
to produce the selected opioid compounds starting from sugar. They combined
enzyme discovery, pathway and engineering along with strain optimization to
comprehend full opiate biosynthesis in yeast. Synthetic scaffolds, enabling better
liberty to systematize enzymes in a rational approach have been applied to attain
higher production of phytochemicals. E. coli synthetic protein scaffolds were used to
co-localize enzymes converting naringenin or eriodictyol to improved
concentrations of catechin. Similarly, DNA and RNA scaffolds have been utilized
to co-localize enzymes related to enhanced production of l-threonine, pentadecan
and succinate in E. coli. Progress in synthesizing hybrid transcription factors or
synthetic RNA switches can assist in the dynamic regulation of heterologous and
endogenous enzymes to fine-tune phytochemical biosynthesis (Li et al. 2018).
Terpenoids play essential roles in maintaining plant cell membrane fluidity,
resistance to herbivores or plant–environment interactions. They are economically
significant pharmaceuticals, aromatics and budding next-generation biofuels. With
the increasing demand for novel terpenoids with superior bioactivities, tailor-made
terpenoid biosynthesis is another important objective for SynBio projects. For
example, de novo monoglycosylated triterpene saponin is synthetically fabricated
15 Plant Synthetic Biology: A Paradigm Shift Targeting Stress Mitigation,. . .
471
the fabrication of these compounds in heterologous host organisms. Thus, Carvalho
et al. (2017) explored an alternative strategy where microbial production can support
the design of novel cannabinoids with enhanced properties by the incorporation of
tailored enzymes. They suggested that a chassis organism can also be designed for
the scalable biosynthesis of less-abundant cannabinoids whose efficacy as medical
drugs can be further tested. Zirpel et al. (2017) also reconstituted biosynthetic
pathway for THCA production from C. sativa in microbial host—Komagataella
phaffii by combining the bacterial prenyltransferase NphB with the THCA forming
enzyme. The WHO classifies opioids as a significant class of medicines that consist
of medication like analgesic morphine and the antitussive codeine (World Health
Organization 2013). All natural opiates (morphine, codeine) and semi-synthetic
opioids (oxycodone, hydrocodone, hydromorphone) are presently obtained from
the opium poppy (Papaver somniferum). Susceptibility of poppy farming to biotic
factors and increasing market demands are growing pressure on the only resource of
opioids. Even, their industrial synthesis has been reported to be commercially
uncompetitive (Reed and Hudlicky 2015). This challenge related to poppy supply
can be addressed by microbial-based synthesis of opioids or their precursor
benzylisoquinoline alkaloids (BIAs). With SynBio technique, biosynthesis of
BIAs downstream of (S)-reticuline, can be reconstructed in Escherichia coli
(Nakagawa et al. 2011) and yeast (Trenchard et al. 2015) from sustainable carbon
and nitrogen resources. DeLoache et al. (2015) and Trenchard et al. (2015)
engineered the biosynthetic pathway, from tyrosine to (S)-reticuline, (Thodey et al.
2014) engineered the pathway from thebaine to morphine and (Fossati et al. 2015)
from (R)-reticuline to codeine. However, it is difficult to design fully functional
entire biosynthetic pathway of 20 heterologous genes essential for their absolute
synthesis. Galanie et al. (2015) engineered yeast with 21 (thebaine) and
23 (hydrocodone) enzyme activities from plants, mammals, bacteria and yeast itself,
to produce the selected opioid compounds starting from sugar. They combined
enzyme discovery, pathway and engineering along with strain optimization to
comprehend full opiate biosynthesis in yeast. Synthetic scaffolds, enabling better
liberty to systematize enzymes in a rational approach have been applied to attain
higher production of phytochemicals. E. coli synthetic protein scaffolds were used to
co-localize enzymes converting naringenin or eriodictyol to improved
concentrations of catechin. Similarly, DNA and RNA scaffolds have been utilized
to co-localize enzymes related to enhanced production of l-threonine, pentadecan
and succinate in E. coli. Progress in synthesizing hybrid transcription factors or
synthetic RNA switches can assist in the dynamic regulation of heterologous and
endogenous enzymes to fine-tune phytochemical biosynthesis (Li et al. 2018).
Terpenoids play essential roles in maintaining plant cell membrane fluidity,
resistance to herbivores or plant–environment interactions. They are economically
significant pharmaceuticals, aromatics and budding next-generation biofuels. With
the increasing demand for novel terpenoids with superior bioactivities, tailor-made
terpenoid biosynthesis is another important objective for SynBio projects. For
example, de novo monoglycosylated triterpene saponin is synthetically fabricated
15 Plant Synthetic Biology: A Paradigm Shift Targeting Stress Mitigation,. . .
471