et al. (2020) created a new photosystem, i.e. an in vivo fusion of PSI and the [FeFe]
hydrogenase from a gene transplanted into the chloroplast chromosome (by insertion
of the HydA sequence into the PsaC subunit). Photosynthetic flow in the
re-engineered chloroplast is diverted from CO 2 fixation (i.e. using electrons from
water splitting and the photosynthetic electron transport chain) to proton reduction
and resulted in biohydrogen production at high rates in a light-dependent fashion. To
maximize the usefulness of such engineered systems, Kanygin et al. (2020) have
positioned redox enzymes to directly capture electrons at the most reductive potential from PSI, i.e. FA/FB clusters before they enter the general cellular pool. These
chimeric proteins also constrain O 2 evolution from PSII, thereby preserving hydrogenase activity, proton pumping and ATP production carried out by the PETC, thus
maintaining cell viability. Thus, re-engineering the elementary route in photosynthetic microorganisms offers an inexpensive and renewable proposal for creating
biofactories capable of driving novel redox chemistries, from renewable resources
like sun and water.
15.7 Increasing the Nutritional Value of Crop Plants
At present agriculture system is incapable to meet global requirements for the
production of reasonable quantity of nutritious foods vital for healthy diets. To
ensure that the world’s population has access to abundant, secure and nourishing
food, future research needs to focus on breeding for the nutritional value of crop
plants under the context of climate change. Nutrition-sensitive cellular agriculture
has endless prospects that seek to guarantee the production of diverse nutrientpacked foods with an extended shelf life, as well as foods tailored for specific
preferences to fulfil the nutritional needs of populations in a sustainable approach
(FAO 2017). Plants can provide all dietary macro and micronutrients, however,
micronutrients are generally unevenly distributed between plant species and even in
different tissues of a particular plant. For example, a good quantity of micronutrients
like iron (Fe), folate, provitamin A and vitamin E are present in non-edible rice
lamina while in minimal amounts in the edible endosperm. Thus, deficiency of
Vitamin A prevails in places where rice is the chief ingredient of not so diverse
diet. The Golden Rice technology—known as GR2—employs two pathways genes,
one coding for phytoene synthase (from maize) and second for carotene desaturase
(from the bacterium Pantoea ananatis), leading to higher synthesis and amassing of
beta-carotene (provitamin A) in the endosperm (Beyer 2010). Moreover, the industrial manufacture of vitamin B12 (primarily from the fermentation of Pseudomonas
denitrificans and Propionibacterium freudenreichii) is not keeping pace with the
demands of the growing population. Fang et al. (2018) engineered fast-growing,
genetically tractable species E. coli to fabricate vitamin B12 (adenosylcobalamin) by
heterologously expressing 28 genes from Rhodobacter capsulatus, Brucella
melitensis, Sinorhizobium meliloti 32,020, S. typhimurium and Rhodopseudomonas
palustris that are separated into six engineered modules.
15 Plant Synthetic Biology: A Paradigm Shift Targeting Stress Mitigation,. . .
465
hydrogenase from a gene transplanted into the chloroplast chromosome (by insertion
of the HydA sequence into the PsaC subunit). Photosynthetic flow in the
re-engineered chloroplast is diverted from CO 2 fixation (i.e. using electrons from
water splitting and the photosynthetic electron transport chain) to proton reduction
and resulted in biohydrogen production at high rates in a light-dependent fashion. To
maximize the usefulness of such engineered systems, Kanygin et al. (2020) have
positioned redox enzymes to directly capture electrons at the most reductive potential from PSI, i.e. FA/FB clusters before they enter the general cellular pool. These
chimeric proteins also constrain O 2 evolution from PSII, thereby preserving hydrogenase activity, proton pumping and ATP production carried out by the PETC, thus
maintaining cell viability. Thus, re-engineering the elementary route in photosynthetic microorganisms offers an inexpensive and renewable proposal for creating
biofactories capable of driving novel redox chemistries, from renewable resources
like sun and water.
15.7 Increasing the Nutritional Value of Crop Plants
At present agriculture system is incapable to meet global requirements for the
production of reasonable quantity of nutritious foods vital for healthy diets. To
ensure that the world’s population has access to abundant, secure and nourishing
food, future research needs to focus on breeding for the nutritional value of crop
plants under the context of climate change. Nutrition-sensitive cellular agriculture
has endless prospects that seek to guarantee the production of diverse nutrientpacked foods with an extended shelf life, as well as foods tailored for specific
preferences to fulfil the nutritional needs of populations in a sustainable approach
(FAO 2017). Plants can provide all dietary macro and micronutrients, however,
micronutrients are generally unevenly distributed between plant species and even in
different tissues of a particular plant. For example, a good quantity of micronutrients
like iron (Fe), folate, provitamin A and vitamin E are present in non-edible rice
lamina while in minimal amounts in the edible endosperm. Thus, deficiency of
Vitamin A prevails in places where rice is the chief ingredient of not so diverse
diet. The Golden Rice technology—known as GR2—employs two pathways genes,
one coding for phytoene synthase (from maize) and second for carotene desaturase
(from the bacterium Pantoea ananatis), leading to higher synthesis and amassing of
beta-carotene (provitamin A) in the endosperm (Beyer 2010). Moreover, the industrial manufacture of vitamin B12 (primarily from the fermentation of Pseudomonas
denitrificans and Propionibacterium freudenreichii) is not keeping pace with the
demands of the growing population. Fang et al. (2018) engineered fast-growing,
genetically tractable species E. coli to fabricate vitamin B12 (adenosylcobalamin) by
heterologously expressing 28 genes from Rhodobacter capsulatus, Brucella
melitensis, Sinorhizobium meliloti 32,020, S. typhimurium and Rhodopseudomonas
palustris that are separated into six engineered modules.
15 Plant Synthetic Biology: A Paradigm Shift Targeting Stress Mitigation,. . .
465