chloroplast – BioQuakes

Tag: chloroplast

Have you ever gotten a painful sunburn while lying on the beach? Have you been as burnt as a ripe tomato in the warm sun, yet one of your friends has a perfect, golden tan? In a recent study, researchers found that tomatoes and maize have leaves that react similarly to this common scenario, with photosynthetic activity being the product of a fluctuating light source.

Tomato plants growing in “Bostanie” Community Garden, Skopje, Macedonia.

In this November study, researchers investigated the role of ATP synthase in chloroplast photosynthesis under changing light conditions, focusing on leaves from tomatoes and maize. According to the University of Cambridge, ATP synthase is a “complex molecular machine” found in the chloroplasts and mitochondria of a plant cell. This enzyme produces the primary energy source of the cell, adenosine triphosphate (ATP), by catalyzing the formation of ATP energy using adenosine diphosphate (ADP) and an inorganic phosphate.

Illustrated diagram of ATP synthase catalyzing the formation of ATP and water molecules.

The team tracked the transitions between sun and shade environments for the crops from sun-to-shade and shade-to-sun, respectively. The researchers essentially measured the levels of gas exchange, chlorophyll fluorescence, and “electrochromic shift signals” in the different light amounts for the tomato and maize leaves, noticing an interesting pattern.

From their tests, the research team found that in the sun-to-shade light transition environments, the ATP synthase activity increased in the leaves of the tomato plant. In the case of the maize leaves, the enzyme activity and available carbon dioxide (CO2) in the atmosphere were unaffected by the fluctuating light.

In the shade-to-sun light transition, the ATP synthase activity also increased in the leaves of the tomato plant. However, while the enzyme activity in the maize leaves remained high, the team found that the amount of atmospheric (CO2) in this transition was greatly restricted by “stomatal conductance, mesophyll conductance and Rubisco carboxylation in tomato” — which simultaneously increased with the increased activity of the ATP synthase enzyme.

Specifically, stomatal conductance is the rate at which gases, such as CO2, flow through the leaves’ stomata. In this way, having a high stomatal conductance means more CO2 can enter the leaf for photosynthesis. According to the RIPE project, mesophyll conductance is the “ease with which CO2 can diffuse from the leaf air space into the chloroplasts” — critical for photosynthesis. Lastly, rubisco carboxylation capacity describes the ability of the enzyme rubisco, which is responsible for carbon fixation in the Calvin cycle, to catalyze the reaction of CO2 with Ribulose, 1.5-biphosphate (RuBp) to synthesize sugar molecules at the end of photosynthesis.

Stomate in a tomato leaf.

Having a high stomatal conductance, mesophyll conductance, and rubisco carboxylation capacity allowed for the maize leaves, especially, to efficiently take in CO2 for photosynthesis in the different light transitions. The researchers noted these distinct factors in their study, deducing that targeting chloroplast ATP synthase and its efficiency was key for “improving dynamic photosynthesis.”

As we have learned in AP Biology, photosynthesis is a two-stage, endergonic process in which plant cells use light energy, water, and carbon dioxide to release oxygen and produce glucose. The process includes the light-dependent reactions and the Calvin cycle, which both occur in various parts of chloroplasts. Particularly, the light-dependent reactions occur in the thylakoid membrane of a plant cell’s chloroplasts while the Calvin cycle takes place in the organelle’s stroma.

We learned in class that in this first stage, light energy is captured by the pigments in photosystem II to eventually make the energy-storage ATP molecule and the reduced electron carrier NADPH. Important to the study, ATP energy is generated in the light-dependent reactions through the process of chemiosmosis, which involves the movement of hydrogen ions down their concentration gradient and across the intermembrane space through ATP synthase — the very enzyme the researchers studied!

Fruit on display at La Boqueria market in Barcelona, Spain.

Ultimately, research like this is crucial to our collective understanding of the biological processes that occur around us in nature. Learning about the current innovative work of these researchers is incredibly fascinating, as their work could be used to improve photosynthesis in wildlife in groundbreaking ways. So maybe next time you are buying fresh produce, you will think of all the amazing ways photosynthesis affects both you and your next meals!

Plants’ Photosynthetic Machinery Functions inside Hamster Cells

By avalution

On January 20, 2025

In Student Post

Scientists have achieved a fascinating breakthrough by transplanting chloroplasts from algae into hamster cells, allowing them to photosynthesize and produce energy for up to two days. This experiment, recently published in Proceedings of the Japan Academy, Series B, could open new doors in biotechnology and cellular engineering.

Researchers from the University of Tokyo sought to replicate the mechanism in mammalian cells after being inspired by sacoglossan sea slugs, which naturally use chloroplasts from their algae diet to produce energy. The scientists used robust chloroplasts from red algae, which flourish in harsh conditions, to successfully transplant chloroplasts into fungal cells, although earlier attempts to do so quickly destroyed the cells.

After carefully separating the chloroplasts, the researchers changed the growth media to allow the hamster ovary cells to naturally absorb the organelles rather than putting them in using force. After entering, the chloroplasts remained structurally sound and carried out electron transport, which is an essential part of photosynthesis, for 48 hours before breaking down.

There are still difficulties in spite of this progress. Animal cells lack the genes necessary to support chloroplasts long term, and thus depend on protein assistance to function. By inserting genes linked to photosynthesis into animal cells, researchers hope to fix this issue and possibly extend the survival and utility of the cells.

Looking ahead, these findings could lead to groundbreaking applications such as photosynthetic materials that capture carbon dioxide or boost oxygen production in lab-grown tissues. However, as it would require an unfeasible quantity of surface area covered in chloroplasts, the idea of solar-powered humans is still unattainable.

In our AP Biology class, we have learned about the endosymbiotic theory, which explains how organelles like mitochondria and chloroplasts originated from symbiotic relationships between primitive cells. According to this theory, a larger host cell engulfed smaller prokaryotic cells capable of energy production, and instead of digesting them, they formed a mutually beneficial relationship. Over time, these engulfed cells evolved into organelles, such as mitochondria for ATP production and chloroplasts for photosynthesis in plant cells. This theory is supported by evidence such as the presence of their own DNA and double membranes.

The recent experiment connects to the endosymbiotic theory by demonstrating how animal cells can temporarily host chloroplasts and perform photosynthesis. It provides a modern-day parallel to the evolutionary process that occurred billions of years ago, suggesting that under the right conditions, symbiotic relationships could potentially be engineered in the lab. This research could deepen our understanding of cellular evolution and pave the way for innovative applications in synthetic biology.

Personally, I find this research incredibly exciting because it highlights how science can push the boundaries of what’s possible. Could we one day engineer cells to create their own energy from sunlight? What other possibilities might arise from blending plant and animal biology? I’d love to hear your thoughts—leave a comment!

What if?… Solar Power for Hamsters

By kuromosomes

On January 9, 2025

In Student Post

In a recent experiment, biologist Sachihiro Matsunaga and a team of researchers transplanted chloroplasts from algae into hamster cells. Inside the hamsters, the chloroplasts were able to convert light into energy for two days. This discovery builds on Matsunaga’s early study on sacoglossan sea slugs that “steal” chloroplasts from algae and use them for energy. The researchers improved on unsuccessful past transplanting methods by using chloroplasts from red algae that live in acidic volcanic hot springs and adjusted the algae to help hamster cells take in the chloroplasts. This allowed them to transplant the chloroplasts successfully. Animals can’t, however, start only using transplanted chloroplasts because animal cells don’t have the genes to produce proteins that chloroplasts need to function long-term. Matsunaga’s team wants to fix this by putting photosynthesis-maintaining genes into animal cells. Still, humans will not be able to ever only use chloroplasts because people would need a much larger surface area covered with chloroplasts to make enough energy.

Shifting gears, this reminds me of learning about photosynthesis in our AP Bio Cellular Respiration Unit. Photosynthesis is an anabolic process that creates glucose and an oxygen waste product. To do photosynthesis, electrons and the H+ ions associated with them are transferred between compounds and elements. Losing elections is oxidation and gaining them is reduction. When an electron is lost it must be gained by something else. In photosynthesis, water is oxidized and the electrons lost go to reduce carbon dioxide into glucose.

In conclusion, I think it would be cool if animals could use chloroplasts along with mitochondria to make energy! There are probably so many applications that transplanting chloroplasts could have if the process gets advanced enough. What do you think?

How Do Guard Cells Attain Energy?

By joelesterol

On February 15, 2022

In Student Post

Ever since we were young, we understood that plants utilize photosynthesis for energy, releasing oxygen in the process. But, we did not learn which parts of the plant actually perform photosynthesis. This is highlighted by guard cells, the cell located in the upper epidermis that controls the concentration of Carbon Dioxide in the plant. So how do they contribute to photosynthesis?

Stomata & Guard Cells

The team of Dr. Boon Leong Lim at HKU wanted to observe the real-time production of ATP and NADPH in the mesophyll cell chloroplasts, which was done by using planta protein sensors in a model plant, Arabidopsis thaliana. This plant is specifically used due to its small genome, short life cycle, simple process to mutagenize, and easily identifiable genes. Shockingly, the Guard Cells Chloroplasts have not detected any ATP or NADPH production whatsoever. Looking for answers, the researchers decided to contact Dr. Diana Santelia, an expert in cell metabolism. Throughout a decade of research and collaboration, they finally have an answer.

Unlike mesophyll cells, photosynthesis in the Guard Cells is inadequately regulated. This is because synthesized sugars from the mesophyll cells are imported into the Guard cells, in which is used ATP production for the opening of the stomata. Additionally, Guard Cells chloroplasts take cytosolic ATP through nucleotide transporters on the chloroplast membrane for starch synthesis throughout the day. At night, though, Guard Cells degrade starch into sugars for the opening of the stomata. Mesophyll Cells, on the other hand, synthesize starch and export sucrose at dawn. Thus, the chloroplasts of Guard Cells ultimately serve as starch storage for the opening of the stomata. Their function is closely linked to that of MCs in order to effectively coordinate CO2 absorption through stomata and CO2 fixation in MCs.

Although the Guard Cells seem redundant, their role in the overall process of photosynthesis is absolutely necessary. As seen in AP Bio, the stomata are essential for gas exchange for photosynthetic reactions. The stomata’s main role is to take in Carbon Dioxide and release Oxygen, both of which are necessities for the reaction to occur.

Thank you so much for reading this blog, and let me know what you think in the comments below!

Colorless Coral?

By biolivcious

On September 25, 2013

In Student Post

wildsingapore.com on flickr

When one usually thinks of a coral reef they think of bright vibrant colors… this may not be the case anymore. A recent study has found that climate change may be depleting coral of its color. In a process called “bleaching” the color is removed from the coral when the symbiotic algae that provide nutrients to the coral either lose their photosynthetic pigmentation and their ability to perform photosynthesis or disappear entirely from the coral’s tissue.

While this strange and disturbing phenomenon has been receiving a lot of attention, there is very little concrete knowledge about the exact molecular process that causes the bleaching. Many hypothesized that the bleaching is a result chloroplast damage due to heat stress, which results in the production of toxic, highly reactive oxygen molecules during photosynthesis, they are linking the origin of the heat stress back to climate change.

To test this theory a team of researchers from Carnegie led by Arthur Grossman and accompanied by a few other scientist from Stanford conducted a study that resulted in the surprising discovery that the bleaching occurs when the algae is not performing photosynthesis, while it is surprising the team also concluded that it could be beneficial to aid in the fight against coral decline. “This is surprising since it means that toxic oxygen molecules formed in heat-damaged chloroplasts during photosynthetic reactions during the light are likely not the major culprits that cause bleaching.” (biologynews.net)

While their initially theory was incorrect, this research has now motivated further study into the molecular functions of coral as well as further efforts toward coral preservation.

http://www.biologynews.net/archives/2013/09/05/clues_in_coral_bleaching_mystery.html

BioQuakes

AP Biology class blog for discussing current research in Biology

Tag: chloroplast

Tanning Tomatoes and Maize: Restricted Photosynthesis in Fluctuating Light

Plants’ Photosynthetic Machinery Functions inside Hamster Cells

What if?… Solar Power for Hamsters

How Do Guard Cells Attain Energy?

Colorless Coral?

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