Information on two rare types of photosynthesis could boost agricultural production | Imperial News

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Researchers studied how certain bacteria perform photosynthesis using low-energy light, which could be incorporated into crops to increase production.

By studying how two bacteria perform the difficult chemistry of photosynthesis, a team led by Imperial researchers discovered the trade-offs they make when using low-energy light. This could inform plant genetic engineering that aims to make crop and biomass production more efficient.

Our study is an important first step in understanding the trade-offs between efficiency and resilience in systems that can use far-red light. Professor Bill Rutherford

Plants, algae and cyanobacteria (blue algae) perform photosynthesis to convert light and CO2 in sugars and oxygen. An enzyme called photosystem II performs the first step in this process, using light to extract electrons from water and feed them into the photosynthetic machinery.

Most organisms perform photosynthesis using visible light, which they collect through a pigment called chlorophyll-a. The energy contained in visible light has long been considered the minimum energy needed to do the hard chemistry of extracting electrons from water.

However, some cyanobacteria perform photosynthesis using low-energy far-red light instead of visible light. Giving plants and algae the ability to use far-red light could make crop and biomass production more efficient, because far-red light uses less energy and is abundant.

The ability to use both visible light and far-red light under different conditions would also be a desirable property for crop plants and algae, but researchers needed to understand if there were trade-offs or compromises in the systems. who can do it.

Far red photosynthesis

The team studied cyanobacteria that carry out photosynthesis using far-red light instead of visible light. Acaryochloris marina lives under green sea squirt, shielded from visible light but exposed to stable far-red light, which it collects using the pigment chlorophyll-d instead of chlorophyll-a.

Other recently discovered cyanobacteria can perform photosynthesis using chlorophyll-a when visible light is present, then switch to using the pigment chlorophyll-f, which also absorbs far-red light, when it is in the dark. shade of visible light.

Collections of yellowish drops on a black background.  Some small drops are fluorescent pinkIn 2018, researchers led by a team from Imperial discovered that in one of these cyanobacteria, Chroococcidiopsis thermalisphotosystem II can do hard chemistry using only the lower energy provided by far-red light.

However, in a study published in eLiferesearchers led by the same team at Imperial have shown that photosystem II of cyanobacteria using the pigment chlorophyll-f is less efficient at capturing and using far-red light than photosystem II of those using chlorophyll-d, but that he is more protected from the harmful side effects of too much light.

Lead researcher Professor Bill Rutherford, from Imperial’s Department of Life Sciences, said: “Engineering crops or algae that could use far-red photosynthesis could help boost the production of food and biomass.

“Our study is an important first step in understanding the trade-offs between efficiency and resilience in systems that can use far-red light. This information could help researchers determine which features would be beneficial and under what conditions.

Comparison of photosynthesis

The team discovered that photosystem II of Acaryochloris marina, which lives in constantly shady conditions and always uses chlorophyll-d, is good at capturing and using far-red light. However, when exposed to excess light, it becomes overwhelmed and produces harmful reactive oxygen species, which can kill cells.

Photosystem II of Chroococcidiopsis thermalis, which uses chlorophyll-f only when visible light is absent or scarce, is less efficient than that of Acaryochloris marina at collecting and utilizing far-red light. However, when exposed to excess light, it does not overproduce harmful reactive oxygen species.

Illustration of a plant and some algae with incoming red and far infrared light.  Next to it is a chart explaining that chlorophyll-d is not photodamage resistant but is effective with light use, while chlorophyll-f is the reverse.

The chlorophyll-f II photosystem of Chroococcidiopsis thermalis therefore represents a different compromise compared to the chlorophyll-d II photosystem of Acaryochloris marina: less efficient far-red photosynthesis but better stability and resistance to damage in bright light conditions.

Dr Stefania Viola, a postdoctoral researcher in Imperial’s Department of Life Sciences and first author of the study, said: “Our research suggests that the two types of far-red photosystem II pay a different price to be able to work with less energy, and that this should be taken into account when planning the introduction of far-red photosynthesis in crops or algae.

“The next step for us is to understand the molecular and chemical mechanisms responsible for the functional differences between the two types of far-red photosystem II.”

“Impact of Energy Limitations on Function and Resilience in Longwave Photosystem II” by Stefania Viola et al. is published in eLife.


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