Genetic discoveries have revealed how legumes provide oxygen to symbiotic bacteria in their roots

By yqqlm yqqlm

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71b670eefa38258 - Genetic discoveries have revealed how legumes provide oxygen to symbiotic bacteria in their roots

in return, plants place bacteria in root nodules to provide sugar and oxygen. The amount of oxygen needs to properly support this symbiotic relationship. Bacteria need oxygen to promote their chemical reactions, but too much oxygen will inhibit a key enzyme, which will turn nitrogen in the air into ammonia that plants can use

the plant’s solution to this “oxygen paradox of biological nitrogen fixation” is a molecule called leghemoglobin. Like hemoglobin, which carries oxygen in our blood, hemoglobin bean combines with oxygen and turns red; It makes the nodules of legumes pink. So far, it is not clear how plants control the yield of this molecule

the team has identified two transcription factors that control how much leghemoglobin is produced in legume nodules

“this gives us a key understanding of how legumes create the micro oxygen environment required for nitrogen fixation. This knowledge is very useful for improving the nitrogen fixation of legumes and is also crucial for transferring tuberculosis to non legumes,” explained Dr. Jeremy Murray, corresponding author and head of cepams group. “Although many genes involved in other tuberculosis processes have been identified, this is the first breakthrough in the gene regulatory network directly involved in the control of nitrogen fixation.”

this study was conducted by a cooperative group led by Dr. Jiang Suyu of Dr. Jeremy Murray’s research group, which is located in Shanghai center of excellence in plant and Microbial Sciences (cepams), Chinese Academy of Sciences, The center of excellence in Molecular Plant Sciences (CEMPs) of the Chinese Academy of Sciences, in cooperation with Dr. Pascal GAMAS and Dr. Marie Fran ç oise jardinaud of lipme, University of Toulouse, France

the research team used the demonstration legume Medicago truncatula to study a protein family in the plant, and several members of the family play a role in tuberculosis. They studied which proteins in this family were produced in symbiotic tuberculosis and found that there were two proteins – Nin and nlp2, and when these proteins were inactive, nitrogen fixation decreased. This indicates that they are involved in nitrogen fixation

for further investigation, they planted plants in an air culture system without soil so that nodules could be observed, and found that plants lacking Nin and nlp2 were smaller in size, nodules were smaller and lighter in color. Careful observation shows that their bean hemoglobin level is low. Further experiments showed that Nin and nlp2 directly activated the expression of bean hemoglobin gene

“this research project was purely driven by curiosity. At the beginning, we only knew that the transcription factors we studied were highly and specifically expressed in nitrogen fixing cells. At first, we didn’t know any connection with bean hemoglobin,” Dr. Murray said

this study also has an in-depth understanding of the evolution of this important symbiotic relationship. They found that other members of the transcription factor family regulate the production of non symbiotic hemoglobin found in plants, which are involved in plant response to hypoxia levels

Jeremy further explained: “this is very exciting because it shows that these transcription factors and their hemoglobin targets are recruited into tuberculosis as modules to help improve the energy of nitrogen fixing cells, so that people rarely see how this symbiotic relationship evolves.”