Nodule symbiosis signal transduction, soybean hits a set of combo punches

Root nodule symbiosis signal "transduction", soybean hits a set of "combined punches"

Nodule symbiosis signal "transduction", soybeans play a set of "combined punches" Nodule symbiosis signal "transduction", soybeans play a set of "combination punches"

The expression pattern of GmROP9a promoter fused with GUS gene in soybean nodules.
Photo courtesy of Gao Jinpeng

The expression pattern of GmROP9a promoter fused with GUS gene in soybean nodules.
Photo courtesy of Gao Jinpeng

Model diagram of ROP involved in nodulation symbiosis signal transduction Photo courtesy of Gao Jinpeng

Model diagram of ROP participating in nodulation symbiosis signal transduction Photo courtesy Gao Jinpeng Model diagram of ROP participating in nodulation symbiosis signal transduction Photo courtesy of Gao Jinpeng

The symbiotic relationship between legumes and rhizobia relies on the complex molecular signal exchange process between plants and rhizobia
.

The contact between the two will trigger the initiation of symbiotic signal transduction, but the molecular mechanism of symbiotic signal transmission from the membrane receptor to the downstream is still unclear

On July 2, "Contemporary Biology" published online the latest results of Wang Ertao's research group, a researcher at the Center for Excellence in Molecular Plant Science of the Chinese Academy of Sciences.
They used soybean, the most important crop of the leguminous family, as the research object, and revealed the initial signal of nodule symbiosis New mechanism for transmission downstream
.

It is not easy to study the nodule symbiosis mechanism of soybean

It is not easy to study the nodule symbiosis mechanism of soybean

Leguminous plants, such as soybeans, peanuts, alfalfa, etc.
, are important crops and economic crops, which directly or indirectly provide humans with abundant nutrients
.

In addition, legumes also play a vital role in the ecosystem
.

They coexist with the nitrogen-fixing rhizobia in the soil, and then fix the free nitrogen in the air into nitrogen-containing compounds that can be used by themselves

This nitrogen fixation is a "unique skill" of legumes as a representative plant
.

Scientists have always wanted to figure out the underlying mechanism, with a view to applying it to other crops that do not have natural nitrogen fixation

However, research on the symbiotic nitrogen fixation of legume root nodules is often concentrated in the model plants Lotus japonicus and Medicago truncatula
.

There are relatively few studies on soybean, the most important leguminous crop .

This is because "Soybean is an ancient tetraploid, with a larger genome and more genes, so genetic manipulation is more difficult, and research on it is time-consuming and labor-intensive
.

" The corresponding author of the paper, Wang Ertao, told the Chinese Journal of Science that the receptor-like kinases NFR1 and NFR5 on the cell membrane of legumes can recognize the nodulation factors secreted by rhizobia and stimulate the initiation of symbiotic signal transduction

"However, the molecular mechanism of the transmission of symbiotic signals from membrane receptors to downstream is not yet clear
.

" Gao Jinpeng, the first author of the paper, told China Science Daily that to study downstream regulatory mechanisms, one must rely on genetic manipulations at the molecular level, with complex choices.

China is the country of origin of soybeans
.

Large-scale soybeans have been planted since the Zhou Dynasty more than 3,000 years ago .

Although Wang Ertao's team did not have soybean genetic transformation technology and platform in the early stage, they still chose soybean as the research object to conduct rhizobia symbiosis experiments.
Through learning and cooperation with multiple laboratories, they overcome difficulties and finally successfully carried out soybean genetic experiments
.

 

How the symbiosis signal is transmitted downstream

How the symbiosis signal is transmitted downstream

Gao Jinpeng told the Chinese Journal of Science that ROP is a unique type of small G protein in plants, which can regulate many processes in plant growth and development as a molecular switch
.

Some studies have shown that ROP is involved in symbiotic events such as rhizobia infecting legumes and nodule formation

Therefore, their research revolves around the molecular processes related to ROP
.

Gao Jinpeng introduced that the activation of ROP is finely regulated by the upstream guanylate exchange factor GEF
.
The guanylate exchange factor GEF can receive the initial symbiosis signal stimulated by the receptor-like kinases NFR1 and NFR5
.

They used soybean ROP genetically modified roots, exposed to rhizobia for 6 hours, and tested their viability
.
It was found that the active form of ROP increased
.
"This provides evidence that ROP is directly activated by rhizobia signals, indicating that ROP plays an important role in the process of soybean symbiosis
.
" Gao Jinpeng said
.

It turns out that the receptor proteins NFR1 and NFR5 can phosphorylate the guanylate exchange factor GEF after sensing the Rhizobium signal, which activates the GEF that has been in a self-inhibited state, thereby catalyzing the activity of ROP and increasing the activated ROP
.

The activated ROP can deactivate other proteins to transmit symbiotic signals
.
"Without GEF and ROP, soybean symbiotic nodulation will be significantly inhibited
.
" Gao Jinpeng said
.

They also found an interesting phenomenon: the active ROP can form a complex with the receptor-like kinases NFR1 and NFR5, and the scaffold protein RACK1, and transmit symbiotic signals together
.

"This implies that ROP can enhance the ability of NFR1 and NFR5 to transmit signals downstream
.
At the same time, other studies have found that the scaffold protein RACK1 can interact with many proteins, which also implies that symbiotic signals may be transmitted to those interacting proteins through the scaffold protein.
, Expand the symbiosis signal
.
" Gao Jinpeng said, but the subsequent signal transmission mechanism is still unclear
.

"Our study reported the GEF, ROP, and RACK1 genes in soybean for the first time, and initially analyzed the role of these genes in the soybean rhizobia symbiosis signal, and revealed a new mechanism of the root nodule symbiosis signal from the cell membrane receptor to the downstream
.
” Gao Jinpeng said
.

Wang Ertao emphasized that the symbiosis and interaction of soybean and rhizobia is very complicated.
Only by fully understanding the symbiotic signaling pathway can it be possible to make better use of the unique advantages of soybean rhizobia symbiosis to achieve high-efficiency biological nitrogen fixation of crops and use less fertilizer
.
Furthermore, under the premise of applying less chemical fertilizers, the yield and quality of soybeans in our country will be improved, the sustainable development of our country's agriculture will be promoted, and food security will be guaranteed
.

Related paper information:

https://doi.
org/10.
1016/j.
cub.
2021.
06.
011