Chinese scientists discover alkali-resistant gene! Increased grain production is just around the corner

In the early morning of March 24, 2023, the research team of the Institute of Genetics and Developmental Biology of the Chinese Academy of Sciences, in collaboration with eight institutions including the Institute of Biophysics of the Chinese Academy of Sciences, the Institute of Northeast Geography and Agroecology of the Chinese Academy of Sciences, China Agricultural University, Huazhong Agricultural University, Ningxia University, Yangzhou University and Syngenta Group China, published a major research result in the top scientific journal "Science": the discovery of the major alkali-resistant gene AT1 and its mechanism of action, and field experiments verified that this gene can significantly increase the yield of crops such as sorghum, rice, millet and corn.

This is a study that can be put into practice, and there is field evidence. What exactly does this article talk about? Let us interpret it for you.

01. Salt-alkali land: a major threat to my country's agricultural development

Vast territory and abundant resources, I believe this is a phrase familiar to many people. With an area of ​​9.6 million square kilometers, the motherland has nurtured Chinese people for thousands of years. To this day, this land is still the root of 1.4 billion people's survival.

However, you must have heard another saying: "China uses 7% of the world's arable land to feed 22% of the world's population." This is another miracle created by our country, but also a kind of helplessness. Because the arable land area in our country is really too small, in recent years, our country's No. 1 document every year is in the field of agriculture. Food is the first necessity of the people, and agriculture is the foundation of the national economy and the cornerstone of prosperity.

However, there is a problem that poses a serious threat to our agriculture, and that is the salinization of arable land !

I don't know if you have ever seen saline-alkali land, a piece of good land, but covered with a vast expanse of white. It is not frost or snow, but the enrichment of salt and alkali. In such saline-alkali land, not to mention crops, even those very tenacious weeds find it difficult to grow, and it often becomes a barren land.

Salt-alkali land (Photo source: FAO)

Saline-alkali land is a general term for salt land and alkaline land. The soil affected by neutral sodium salts (such as sodium chloride and sodium sulfate) is called saline land, while the soil affected by alkaline sodium salts (such as sodium carbonate, sodium bicarbonate, and sodium silicate) is called alkaline land.

02. How is saline-alkali land formed?

So, how is saline-alkali land formed? The essence is the imbalance of salt ions in the soil. And this imbalance is caused by multiple factors. Soil moisture is an important source of salt ions. Whether it is rivers and lakes, groundwater irrigation, or the use of fertilizers, they will bring salt ions. If the amount of these salt ions exceeds the absorption capacity of plants and cannot be removed by other factors, these ions will continue to accumulate in the soil with the evaporation of water, and eventually lead to soil salinization.

The relationship between water and saline-alkali land formation (Image source: FAO)

Land salinization is closely related to agriculture, and therefore directly threatens my country's agricultural production. For example, the famous black soil, which is also the northern granary that has nurtured countless Chinese people, has gradually expanded its saline-alkali land area due to years of continuous cultivation, from 24,000 square kilometers in 1950 to 39,000 square kilometers in 2016. Many lands have also changed from mild salinization to moderate to severe salinization.

In fact, not only in the Northeast, but also from the coast of the East China Sea to the northwest border, from the hot Hainan to the cold Songnen Plain, there are saline-alkali land distribution. If we add land acidification and black soil degradation, the arable land involved has reached 660 million mu. What is the scale? According to the third national land survey in 2022, the arable land area in my country is 1.918 billion mu, which means that one-third of the arable land area is facing the "three problems", which will greatly threaten my country's food security and the national economy and people's livelihood.

Salt-alkali land

For this reason, following the proposal of the comprehensive utilization plan and implementation plan for saline-alkali land in the Central Document No. 1 of 2022, the Central Document No. 1 of 2023 continued to focus on the issue of saline-alkali land. This year, it specifically proposed "continued to promote the transformation from mainly managing saline-alkali land-adapted crops to breeding more salt-alkali-tolerant plants to adapt to saline-alkali land, and to carry out pilot projects for the comprehensive development and utilization of saline-alkali land and other reserve arable land resources."

And this is closely related to our article today, that is: developing salt- and alkali-tolerant plants.

03. How to find salt-alkali tolerance genes in plants?

Life always possesses the most tenacious perseverance and can survive in unexpected places.

Although saline-alkali land is a deadly place for many crops, there are always some exceptions. This is the strong stress resistance of plants, that is, the ability of plants to resist certain adverse environments, such as cold resistance, drought resistance, disease and pest resistance, and of course, salt and alkali resistance. Behind this, plant genes play a role.

So, how do we find salt-alkaline tolerance genes? Today's Science article gives us a classic demonstration, so let's take a comprehensive look.

Step one: choose a suitable plant.

There are quite a few salt- and alkali-tolerant plants, but many plants tend to have geographical distribution specificity, so their salt- and alkali-tolerant mechanisms are limited. my country has a vast territory, covering various climate zones including tropical, subtropical, temperate and frigid zones. Therefore, it is crucial to find a crop that can be widely distributed and has a large span of variation as a research object.

Traditional research likes to use the classic model plant, Arabidopsis thaliana, but this plant did not originate from saline-alkali land, so it has natural defects when studying salt-alkali tolerance.

After extensive research and experiments, scientists chose sorghum , a salt-tolerant crop, as their research object. Sorghum is a crop that originated in the barren land of central Africa and has spread throughout the world. Its ability to survive in multiple regions and in soils with different salinities is enough to prove that it has strong salt-tolerant ability.

Sorghum (Image source: Wikipedia)

Step 2: Appropriate research system.

With the right salt-tolerant plants, the next step is to have a suitable research system. Soil salinization is mainly caused by sodium carbonate or sodium bicarbonate. In order to simulate soil salinization, traditional research mainly uses these two alkalis to adjust the alkalinity of the experimental system. However, this adjustment process is prone to pH instability. As a result, the experimental system is unstable and the difficulty of repetition increases.

In order to achieve a stable and reliable saline-alkali land experimental system, the research team tried many times and finally determined a mixed alkali (sodium carbonate: sodium bicarbonate = 1:5) system, which can enable the experiment to proceed stably.

With the above research, the next step is to explore the salt-alkali tolerance genes of sorghum.

Step 3: Whole genome big data association, analysis and search for salt-alkali tolerance genes

Genes determine traits. The factor behind plant salt-alkali tolerance is genes. In order to find the salt-alkali tolerance genes of sorghum, the researchers first collected many salt-alkali tolerant sorghum resources. There were great differences in the salt-alkali tolerance of these sorghums.

Growth of different sorghums in a stable saline-alkali system constructed in the laboratory (Image source: Institute of Genetics and Developmental Biology, Chinese Academy of Sciences)

Next, using the method of whole-genome association analysis, scientists obtained the genetic resources of various sorghums, and then conducted association analysis between the traits and the whole genome based on their salt- and alkali-tolerant traits. Ultimately, the researchers successfully located a key gene: AT1.

Significant signal gene AT1 found through genome-wide association analysis (Image source: Institute of Genetics and Developmental Biology, Chinese Academy of Sciences)

The verification of the AT1 gene also confirmed the important role of AT1 in the salt-alkali tolerance of plants. For example, in sorghum, the AT1 gene is obviously related to sorghum's tolerance to salt and alkali. Under high-salt and alkali culture conditions (75mM Alkali), the growth effect of overexpressing AT1 (SbAT1-OE) is significantly worse than that of the control group (SbWT), and even worse than that of the AT1 knockout group (SbAT1-KO).

The AT1 gene plays an important role in sorghum's salt-alkali tolerance (Image source: Institute of Genetics and Developmental Biology, Chinese Academy of Sciences)

Not only that, the AT1 gene is also conserved in many grass plants and can play an effective role, which is of great significance. You know, grass is a major crop family among us, and corn, rice, and millet are all grasses.

The AT1 gene is effective in a variety of crops (Image source: Institute of Genetics and Developmental Biology, Chinese Academy of Sciences)

04. How does the AT1 gene respond to saline-alkali threats?

So how does the AT1 gene cope with the threat of salt and alkali? The researchers studied this gene in mammals and crop system models. The results showed that the AT1 gene mainly copes with high salt and alkali stress by regulating the phosphorylation of aquaporins (plasma membrane intrinsic protein 2s (PIP2s)).

The AT1 gene responds to salt stress through PIP2s (Image source: Institute of Genetics and Developmental Biology, Chinese Academy of Sciences)

In addition, under high salt stress, plants will also produce ROS (reactive oxygen species), which is itself harmful to plants. The AT1 gene can also affect ROS efflux by regulating PIPs. This is the first time that scientists have revealed the molecular mechanism of high salt and alkali resistance in higher organisms.

AT1-regulated salt-alkali stress response mechanism and the utilization of AT1 can improve the yield of various crops on saline-alkali land

05. Field experiments confirm the effectiveness of AT1

Practice is the only criterion for testing truth: Field experiments prove the effectiveness of AT1

In fact, scientists have been studying the mechanism of salt-alkali tolerance for many years and have found many salt-alkali tolerance genes, but many studies have encountered many problems when put into practice. So, can the salt-alkali tolerance gene AT1 discovered by scientists this time play a role in practical applications?

The researchers decided to test the effect of this gene in the field.

First, sorghum was used. The research team carried out salt-alkali tolerance breeding and then carried out field experiments. The saline-alkali land in Pingluo, Ningxia, which has a pH value of 8.5-9.1, is moderately saline-alkali land.

The results are very encouraging.

The use of the AT1 gene can increase sorghum grain yield by 20.1% and the whole plant biomass (for silage) by nearly 30.5%. This result shows that AT1 is not only feasible in mechanism, but also has significant effects in practice.

AT1 gene knockout increases sorghum yield on saline-alkali land (Image source: Institute of Genetics and Developmental Biology, Chinese Academy of Sciences)

Of course, the significance of the AT1 gene is not just to regulate the salt and alkalinity tolerance of sorghum. It is a gene that is conserved in many crops, including our important food crops - rice, corn and millet.

The researchers then conducted further field experiments on these crops. The results showed that the millet modified by the AT1 gene could increase the yield by nearly 19.5% on the saline-alkali land in Pingluo, Ningxia, which is equivalent to increasing the yield by one-fifth. The survival rate of corn modified by the AT1 gene in saline-alkali land was also significantly enhanced.

Growth phenotypes of SbWT and SbAT1ko in saline-alkali land (salt content 0.7%, pH 8.5) in Pingluo County, Ningxia Province in 2022 (Image source: Institute of Genetics and Developmental Biology, Chinese Academy of Sciences)

Moreover, this gene also showed good cross-regional effects .

In the saline-alkali land of Da'an, Jilin, northeast China, more than 1,600 kilometers away from Pingluo, Ningxia, the pH is as high as 9.17. Researchers planted rice, millet and corn modified with AT1 genes, and the annual yield of different crops increased by about 24.1% to 27.8%, an increase of one-quarter.

(AT1/GS3 knockout improves rice yield in saline-alkali soil (Image source: Institute of Genetics and Developmental Biology, Chinese Academy of Sciences))

Field experimental research has fully demonstrated the power of the AT1 gene, which can directly enable plants to survive better in saline-alkali land and increase yields.

06. Benefits to the present and future generations

Food is the primary need of the people, and the food issue concerns the fundamental interests of all mankind. According to a report by the Food and Agriculture Organization of the United Nations, 45 countries in the world currently need food aid, and some people in six of these countries are facing the highest level of food shortage and are about to fall into catastrophic hunger. In addition, millions of people are facing severe hunger.

Salt-alkali land often occurs in cultivated land, which seriously threatens food security. According to the United Nations Food and Agriculture Organization, as of 2015, more than 1 billion hectares of land in the world have salinization problems, while there are only 1.5 billion hectares of cultivated land in the world. If we can develop even 20% of salt-alkali land, it will contribute at least 250 million tons of food production to the world. This will greatly alleviate the food crisis and save more people from hunger.

Therefore, developing more salt- and alkali-tolerant crops is of great significance for alleviating the global food crisis and saving more lives.

It is particularly worth mentioning that the AT1 gene discovered by the research team this time has a very significant effect on important grass crops such as rice, corn and millet. You should know that corn and rice are the first and second largest crops in the world and are the main source of food for people all over the world. Therefore, if this genetically modified crop can be widely promoted, it will bring major changes to the world.

It can be said that the benefits to the present will last for generations to come!