Yang Wenqiang
Researcher of the Institute of Botany, Chinese Academy of Sciences, National Botanical Garden
Algae are the oldest organisms in the world, bringing oxygen to the Earth about three billion years ago, and today algae provide more than 80% of the Earth's oxygen and fix the general carbon dioxide. Not only that, but seaweed is also the largest protein "cake" that nature gave to the earth as early as 1 billion years ago. Algae are silently dedicated in many fields and silently guard our home.
Transcript of the speech: The story I bring to you is a story about algae, and I want to tell you how algae protect us and how they are great heroes of mankind.
I would like to ask you a question, the picture on the left is oxygen, do you know where the oxygen we breathe comes from? Many friends know that the oxygen we breathe is the result of photosynthesis, and many people think that it is the plants on land, including plants in forests, that contribute most of our oxygen. But in fact, no, in fact, algae contribute 50% of our oxygen, and some scientists even propose that algae provide 80~90% of human oxygen, and at the same time, the use of this oxygen can form an ozone layer to protect us from ultraviolet rays, so from this point of view, algae is very, very great.
We know that the earth appeared about 4.6 billion years ago, we had life 37~3.5 billion years ago, we had cyanobacteria in 33~3.2 billion years, and single-celled eukaryotic green algae appeared in 15~1.4 billion years, followed by multicellular and macroalgae, which was a little longer. Then a very important event occurred, the plants landed, from the water to the land, the plants and algae separated about 400 million years ago, and mosses, ferns, gymnosperms, and angiosperms appeared one after another. Our hominids appeared about 5 million years ago, so compared to the emergence of algae, the emergence of our humans is too late.
It is because of the appearance of algae that the state of the earth has been changed. We know that the earth is flooded with a lot of carbon dioxide, due to the explosion of aerobic organisms such as algae, crazy photosynthesis has been carried out, a large amount of oxygen has been released, and the concentration of carbon dioxide in the air has been reduced to 300~350 ppm now, and at the same time the oxygen concentration has been increased, so there is 21% of such a concentration so far, so algae is very, very great.
After the algae landed, there were more kinds of plants, our biodiversity, human evolution, and our current world. The beautiful corals in the ocean that you see are all contributions of algae, so algae are also the cornerstone of marine ecosystems and biomes, and it is very, very scary to imagine that without algae.
The living environment of algae is diverse, you can imagine that most of the algae live in the ocean, in the lake, in the soil, in the swamp, and there are many algae that especially like to live in some extreme environments, such as high salt environment, deep sea environment, glacier, snow-capped mountains, deserts, hot springs, extremely acidic or alkaline environments, which provide us with valuable wealth. For example, the energy we use, the oil and natural gas in fossil energy, they are actually from ancient algae, and it can also be said that it is our ancestor algae.
We have used algae in many ways, for example, we have eaten a lot of kelp seaweed, eaten deep-sea fish oil, and also eaten spirulina powder, chlorella powder, and now the more popular astaxanthin, fucoxanthin and so on. In fact, these are all processes in which algae form carbohydrates after photosynthesis, and then form secondary products. In other words, the process of using algae is to use the carbohydrates formed after its photosynthesis, whether it is a primary product or a secondary product. The biodiesel, starch we use, aviation fuel used in aircraft, and many high value-added products, such as algae, are always guarding and guarding us.
As you can see in this picture, the picture on the left is released by NASA in the United States, a chlorophyll fluorescence map of the global ocean, and the one on the right is released by our State Oceanic Administration, and the blue ones in the picture are plankton, that is to say, the algae that are photosynthesizing, which is very, very shocking.
Photosynthesis is deceptively simple, its substrate is water, which is a process of photocatalysis, which cracks water, then fixes carbon dioxide, and finally forms our carbohydrates and releases oxygen. Photosynthesis can be simply divided into a light reaction, and a dark reaction process, you can also understand photosynthesis as a process from light energy through photosynthetic organisms to electrical energy, then from electrical energy to unstable chemical energy, and finally to fix carbon dioxide to form stable chemical energy.
Photosynthesis may seem simple, but in fact it is very delicate and complex. As a result of photosynthesis, we can produce more than 10 kilocalories of free energy per year, and at the same time it can fix 220 billion tons of biomass – 250 billion tons. This amount is about 10 times the amount of energy we humans need each year, and visible photosynthesis is important, and photosynthesis by algae is even more important.
I've been thinking about a question, photosynthesis is so important, its regulation is so fine, how to complete its regulation? Our team uses a very small model organism, Chlamydomonas reinhardtii, the picture on the left is a model diagram, it looks very large, in fact, we can't see it with the naked eye, it is only 5~7 microns, it is a haploid, unicellular, eukaryotic green algae, very good, about 18,000 genes. We see, the main green part is its chloroplast, it has chloroplasts, it has a cell wall, it can carry out photosynthesis, it is a characteristic of a plant, and we see that it has eyes, it can feel light, and flagella can swim and mate, these are typical animal characteristics, so it also creates algae including rhine algae, which has a very special taxonomic status, we call it protists.
The video on the right is a video we took under a microscope of Chlamydomonas reinhardtii swimming. You'll magically find that when one algae goes swimming, there's another algae in front of it, it doesn't hit it, it can see it and avoid it, it's amazing. It has flagella that can swing, and the flagella are very busy in the transportation process, and there are algae, and the flagella can rotate at a speed of 1700 revolutions per second, which is very amazing.
We use genetics to study the regulatory mechanisms of photosynthesis. It's what it looks like, and we go through some physical and chemical methods to make it have some genetic mutations, and after the mutation, we will see what it looks like. At this time, we look for some mutant genes, such as those that can grow in dark conditions, that is, under the conditions of external carbon sources, but cannot be autotrophic and photosynthetic under light.
As you can see in this diagram, we found a lot of mutants that can't grow after seeing light, and we suspect that they may not be able to use light, or they may not be able to photosynthesize efficiently. This is some of the situations in which we cultivate algae on a daily basis, because Chlamydomonas reinhardtii prefers red light and blue light, and this room is very dazzling, and I have to wear goggles every time I go in, so every time I come back, I will proudly say that I have just come back from Las Vegas in Chlamydomonas reinhardikilain, and it feels like a bright light. The picture in the middle is that when we are studying many important genes, including protein functions, we need to know where it is located, whether it is located on the cell membrane, or on the cytoplasm, and chloroplasts, and so on.
I'm thinking about another question, just like we humans work during the day and we need to sleep at night, many of our photosynthetic organisms also need to photosynthesize during the day, but at night they need to respire. During the day, carbon dioxide is fixed and oxygen is released to form carbohydrates, but at night, carbohydrates are degraded and respirated, and carbon dioxide is released at the same time. Photosynthetic organisms that have experienced darkness, once they receive light, they will quickly return to photosynthesis, so how is the darkness regulated? How do photosynthetic organisms adapt to the darkness? This is another scientific question that we are concerned about.
We took the means of genetics to find, this time we looked for the opposite, looking for some mutants that do not grow in dark conditions, and put them in light conditions for photosynthesis, and these mutants, we speculate that the mutation of some genes causes the algae to not complete the process of dark adaptation. After unremitting efforts, we have found a very critical factor called FDX5. We can see the middle picture on the far left, the algae does not grow in the dark, and then we found that FDX5 is particularly powerful, it can regulate fatty acid metabolism, it can regulate membrane lipid metabolism, and it can also regulate redox balance, which can affect the covert adaptation, and then affect the ability of algae to return to light conditions and photosynthesis.
At the same time, in the process of studying dark adaptation, we proposed a very important concept called hydrogen-oxygen reaction. As the name suggests, there is hydrogen here, there is oxygen, and we know that hydrogen and oxygen, mixing together is very dangerous, right? Later, after unremitting efforts, we found a suitable concentration of hydrogen, oxygen, nitrogen and carbon dioxide, which is how we can allow algae to grow in dark conditions, a condition for the outside world to give carbon sources.
In the process of research, people will find that different organs of a plant, such as its fruit, its stalk, its seeds, including the tuber of the potato, have different oxygen concentrations in different parts. Why is its oxygen concentration different? And people have also found that there are many cases where the oxygen concentration in the natural environment is very low, we know that the oxygen concentration in the air is 21%, we call the condition without oxygen the condition of hypoxia, and the series of oxygen concentrations less than 21% and greater than 0 are called hypoxia.
For example, when leguminous plants are nodling and fixing nitrogen, they need an environment that is not oxygen. There is also a type of nitrogen-fixing cyanobacteria in cyanobacteria, which has a unique cell called heterocytes, and there can be no oxygen in the heterocytes, otherwise it is impossible to complete the process of nitrogen fixation with oxygen. And we also found that leaf nodules, a lot of aquatic plants that grow underwater, photosynthesize differently than we normally do. There is also the cancer we are talking about, the oxygen concentration in the cancer cells is very low, and we often do aerobic exercise, etc., which can increase the oxygen concentration to attack the cancer cells and reduce our risk of cancer.
Other scientists have found that oxygen plays an important role in the differentiation of plant stem cells. As you can see, the small orange dots on the diagram show that if the concentration of oxygen changes, it is impossible for plant stem cells to complete normal differentiation, and this phenomenon is also found in the differentiation process of anthers. This also changes our view that anaerobic is just a kind of stress, and we can think of anaerobic as a signal, as a signal, plays a very important role in regulating the growth of organisms.
At the same time, we found that if oxygen is gone, algae can also produce hydrogen. Of course, hydrogen production was discovered by scientists a long time ago, and we systematically summarized how algae use different conditions and different pathways to produce hydrogen, and summarized a total of three hydrogen production pathways. We have also systematically studied how algae release hydrogen. For example, it mainly has a process, as you may know, the concept in biochemistry is called glycolysis, which is to degrade the accumulated starch into pyruvate that we need, and then be degraded into different substrates.
We were thinking that we would change the pathway to produce hydrogen, go up to the red patch in the diagram, and produce more hydrogen. We try to shut down other pathways, but it seems that every time we shut down a pathway, we produce a new compound, which we didn't expect, so the regulation of hydrogen production is very complicated. We have published a lot of articles on regulation, and we have found many interesting phenomena, such as the discovery that Chlamydomonas has two pathways for acetic acid synthesis under dark conditions, one in mitochondria and one in chloroplasts. Later, in this article, we systematically summarized the mechanism of how algae dark anaerobic algae are regulated.
We just talked a lot about the regulation of photosynthesis, how photosynthesis adapts to darkness, including the regulation of conditions such as hypoxia, and so on. The dream of all of us who study photosynthesis is to improve the efficiency of light energy use and make photosynthesis more efficient. Algae have a very efficient photosynthesis capacity, and compared with plants, their theoretical light use efficiency can reach up to 20%, and the highest theoretical value of plants is only 5%. It is found that algae have many differences from plants in terms of living environment, growth ability, environmental adaptability, including light reaction, dark reaction, and light protection ability, so it has such a high light energy use efficiency.
So we wondered if we could use the high light efficiency of algae to apply these scientific findings to crops and improve crop yields. In view of the place where algae photosynthesis occurs, the regulatory mechanism of chloroplasts is similar to many regulatory mechanisms of photosynthesis, but the growth period of our algae is particularly short, for example, like our plants, different places in our country can plant different generations in a year, and they can be planted up to three seasons a year. The factors we excavate in algae, some important regulatory proteins, etc., are applied to crops to modify crop traits.
I always say that the plants around us, whether they are crops or not, they do not exist by our human will, they exist for the purpose of living. The purpose of us people is to make it more productive according to our needs, to make it tastier, taller, shorter, etc., so we have a lot of room to modify them.
The first thing we did was to dig out a very important protein in algae, which we used in rice, and found that it can increase the yield by 30% in the laboratory and 10%~15% in the field, which is still very impressive. At the same time, we also tried this key regulatory protein, and in tomato and lettuce, after using the key protein we excavated, its yield increased very much.
We know that the demand for soybeans in our country is particularly high, but every year, our country produces only 15 million tons of soybeans, and last year we imported more than 100 million tons. We have been wondering if we can work hard to increase our country's soybean production. We dig a lot of algae, genetically related to carbon sequestration to modify soybeans. We see that the first row is the control, and the following rows are all after our transformation, the soybean grains have become larger, and the yield has increased. We hope that these efforts can also be excavated from algae and photosynthesis, and these key factors can be used to improve crops and contribute to the food security of our country.
At present, we have excavated many key factors in algae, for example, one of the key factors of modification is called RuBisCO. What is RuBisCO, which is ribulose 1,5 bisphosphate carboxylase, which is the enzyme that is very important in our photosynthesis and why it can fix carbon dioxide. Most of the RuBisCO in algae has a particularly high activity, so we wondered if we could dig out a few high RuBisCO and replace the RuBisCO in the millet, so that it can achieve more carbon sequestration and make a certain contribution to the production of millet in our country, improving quality and efficiency.
We said that algae have a very unique property that can concentrate carbon dioxide in the environment by more than 1,000 times. This amount is amazing, mainly because it has two very unique organelles, one is called the carboxyl body, and the other is called the protein nucleus. Of course, the passage of carbon dioxide from outside the body into the cell line can be described as breaking through a thousand obstacles, and we call this process the concentration mechanism of carbon dioxide. The mechanism of algae was lost in the process of plant evolution, and we wondered if we could apply the carbon dioxide concentration mechanism in algae, including the carboxyl body in cyanobacteria, the protein nucleus of green algae and other algae, to crops to achieve more efficient carbon sequestration, and we started to work on this part of the work.
At the same time, we are actively involved in a number of other projects, which are also based on algae. We know that our country has a moon landing program, a space program, a Mars program, and so on, and this time our Shenzhou 14 brought back rice seeds. Algae will play a very important role in the aerospace life support system, so we are also involved in some research.
There are now conservative estimates of about 100,000 species of algae, some say 200,000 species, some say 1 million species, and new algae are reported every day. Life on Earth has experienced five mass extinctions, especially the last extinction, 80~90% of all living things have been extinct, but algae still exist. What I want to say is that if the earth experiences the sixth mass extinction, 80%, 90%, or even more organisms are extinct, algae can still exist, mainly because it can adapt well to the environment and photosynthesize very efficiently.
The study of algae is called Phycology, which is very similar to the other word for psychology. So when I was in the U.S., when I was talking to a lot of people, I was talking about Phycology, and people didn't understand and asked, "Are you talking about Psychology?" because they think psychology is very important to them. But I would say that phycology is also very critical. I hope that more people will pay attention to our algae, pay attention to the guardians of our earth, and there will be more young friends, including scientists, who will devote themselves to our algae research in the future.
Source: CC Forum