How to make a difference through plant metabolism

Usually when we consider many of the plants around us, we efficiently visualize using the sun’s electromagnetic radiation through photosynthesis in their leaves – carbon dioxide from the air, as well as water drawn from the soil through their roots and growing rapidly. As they could reasonably. In reality, the efficiency of this process is less than 10% of the input energy, and not all of the different types of plant metabolism that are formed during evolution are the same.

Among the plant metabolisms currently in use, some use significantly more efficient carbon fixation pathways, while others waste a lot of energy gained from photosynthesis through unnecessarily complex processes, especially to deal with waste. How fast plants can grow if they develop the most efficient carbon fixation path has been the subject of several studies over the past few decades, involving everything from grain to tree.

As these studies show us, more than scientific and evolutionary biological curiosity, these genetically engineered plants offer real opportunities in everything from food production to afforestation.

Rediscovery with evolution

Spine vs. cephalopod eyes.  Notice the opposite of the retina (1) and the nerve (2).  Lack of cephalopod spinal blind spot (4).
Spine vs. cephalopod eyes. Notice the opposite of the retina (1) and the nerve (2). Lack of cephalopod spinal blind spot (4).

Over billions of years on Earth, the process of evolution has led to many curious branch paths and events, in addition to creating fascinating biological structures, as well as innovating the same structure differently. For example, the vertebrate and cephalopod eyes, which appear to be independently formed and are both identical and wildly different. This process is called convergent evolution.

As interesting as the wing-like eyes and cohesive features of dinosaurs (birds), mammals, and insects are, perhaps less obvious, but the convergent evolution of photosynthesis is no less important. Over millions of years, rough versions of photosynthesis in early plants have evolved into many distinct photosynthesis pathways, based around all the rubisco (ribulose-1,5-bisphosphate carboxylase-oxygenase) enzymes and the corresponding Calvin cycle.

Most plants use the so-called C3 Carbon fixation, which uses a fairly basic Calvin cycle. Its overall efficiency is at most 3.5% (related to solar radiation energy input), where less common C4 Carbon fixation cycle tops above 4%. C4 And CAM (carcinogenic acid metabolism) is a form of convergent evolution, both of which use phosphoenolpyruvate (PEP) to capture CO2 And thus creates an increased concentration of CO2 Around the RuBiscCO enzyme to reduce photorespiration.

Reaction of the enzyme RuBisCO with carbon-di-oxide and oxygen.
Reaction of the enzyme RuBisCO with carbon-di-oxide and oxygen.

A major problem with RuBisCO is that the responses listed above show that it reacts with both COs.2 And he2, Where the subsequent reaction is clearly undesirable due to the lack of carbon atoms. 2-phosphoglycolate (2-PG, or C)2H.2Oh6P3-) Metabolic products that react with oxygen are toxic to plants because they block certain metabolic pathways and thus have to be dealt with. This is where C is for3 Plant photorespiration is essential, as it allows the conversion of 2-PG to the desired PGA () which is used to make the sugars needed for plant growth, as captured in this graphic by Williams et al. (2013) Metabolic pathways for C.3 And c4 Plants:

C3 and C4 are metabolic pathways of plants.  (Credit: Williams et al., 2013)
C3 and C4 are metabolic pathways of plants. (Credit: Williams et al., 2013)

This tells us that many plants – including food grains and plant species – that use the C3 carbon fixing cycle spend a significant amount of the energy they gain from photosynthesis to break down this 2-PG due to the interaction between them. Is created. RuBisCO and Oxygen. Due to this photorerespiration process, the loss of water through the stoma (pore) also increases.

Since RuBisCO binds more easily to oxygen rather than carbon dioxide as the temperature rises, it has a natural limitation of the effective environmental conditions for C.3 Plant, and explains why c4 And CAM trees in particular are found in warmer, more arid conditions. Thus the logical conclusion is that if we can replace the appropriate components of C4CAM or other pathways such as cyanobacteria are found in C3 Plants, it can significantly increase their growth rate by reducing the energy lost in photorespiration.

Field test

C3 (A) and C4 (B) Plant leaf anatomy diagrams.  The latter divides the CO2 concentration and the Calvin cycle into two cells.  (Credit: Cui, 2021)
C3 (A) and C4 (B) Plant leaf anatomy diagrams. The latter divides the CO2 concentration and the Calvin cycle into two cells. (Credit: Cui, 2021)

After initial attempts to increase the direct involvement of the Rubisco enzyme with carbon dioxide were less successful than successful, the focus shifted to understanding and optimizing in the 1990s, at which time it is generally accepted that engineering C4-style carbon fixation in C3 plants. An effective way forward using existing C4 plants as a template. To make genetic engineering more straightforward, whether a C3 species also has a related C4 species is relevant here. Another active topic of discussion here is following the strategy of one or two cells, as mentioned by Cui (2021).

Other researchers have tried to find fancy ways to improve photosynthesis, such as Nolke et al. (2014), which added the expression of a polyprotein (DEFp) taken from Escherichia coli From glycolate dehydrogenase (GlcDH) to potato plants (Potatoes), Resulting in 2.3 times increase in tuber yield. This same method could potentially be applied to other plants, perhaps with similar yield increases.

Effects of DEFp expression on potato phenotype and tuber yield.  (Noelke et al., 2014)
Effects of DEFp expression on potato phenotype and tuber yield. (Noelke et al., 2014)

Wang et al. (2020) with mixed results Nölke et al. Has reported a modified rice species using a similar method. This study was followed by Nayak et al. (2022) For those who have reported promising results that could lead to GE rice, these changes have been introduced in field trials. Related field trial data are available from South et al. (2019), who conducted field trials using transgenic tobacco plants. These plants have shown an increase of about 40% in useful biomass production compared to wild species.

Clearly, many more experiments and field trials are needed to ensure the effectiveness, long-term stability and overall safety of these changes before distributing any of these GE species to farmers for next year’s crop. Nevertheless, these experiments give a tempting glimpse into a future where today’s agricultural production has increased by 150-200%, with zero additional nutrient requirements, reduced water requirements and much better resistance to heat waves, which is expected to happen a lot. More regular due to ongoing climate change.

Which raises the question of whether similar methods can be used to make regular plants more efficient in fixing carbon from the atmosphere.

A forest while you wait

Conventional wisdom tells us that trees take a long time to grow. Perhaps surprisingly, most plants that are referred to as ‘trees’ (meaning there is no biological definition of ‘tree’) use C.3 Carbon fixation metabolism. In a recent preprint article by Living Carbon Team et al. (2022), a mutation similar to the previously discussed grain-based transgenic species has been reported to be applied to poplars. These hybrid poplars were later planted in the fields of Oregon, as detailed on the Living Carbon team’s website. The preprint article reports a roughly 50% increase in biomass profits compared to Standard Poplar, which will lead to the belief in higher goals on the Living Carbon website.

As explained in the Frequently Asked Questions page for the project, all plants modified in this way are female, so genetic mutations will not spread to other wild poplars through pollen, but only to the planted trees. The project, in partnership with Oregon State University (OSU), has already planted more than 600 of these hybrid poplars. The goal is to plant many of them in the coming years as part of the carbon capture method.

With the potential to significantly increase production from crops, forests that grow 50% faster than conventional forests, it seems we can look forward to an exciting future.

Genetic engineer

A big elephant in the house when it comes to this is genetically modified organisms (GMOs), or “genetically engineered” (GE) as the more accurate term. Many countries have laws that prohibit or strictly prohibit the growth, import and sale of GE organisms, products, seeds, etc. Undoubtedly this would be the biggest hurdle in taking any one of these photosynthetic-enhanced plants.

While many arguments can be made for the underlying protection of these hybrid trees since neither humans nor cattle can consume forests and trees in general, the division between the logical world of science and the emotional world of ordinary people and the news cycle in this daily context is really great.

Nevertheless, with the current course of the world where drought, famine and all the other extremely unpleasant symptoms of climate change will be felt by more and more people, it may be that the tools that science has provided us will save us here. , Allowing us to feed millions of people and make a big hole in the extra CO2 In the atmosphere, carbon builds up and makes plants better.

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