Bemisia tabaci Photo courtesy of Vegetable Research Institute, Chinese Academy of Agricultural Sciences
Bemisia tabaci Photo courtesy of Vegetable Research Institute, Chinese Academy of Agricultural Sciences Photo courtesy of Bemisia tabaci Vegetable Institute, Chinese Academy of Agricultural Sciences Photo courtesy of Vegetable Research Institute, Chinese Academy of Agricultural Sciences "'Using the spear of the son to attack the shield of the son' is an allusion during the Warring States period.
This "unique skill" enables Bemisia tabaci to feed on more than 600 kinds of plants and harm global crops.
On March 25, "Cell" published the results of this collaboration between Chinese and foreign scientists online.
Zhang Youjun (first from right), Xia Jixing (second from right), and Guo Zhao will observe the experimental conditions of Bemisia tabaci on tomatoes.
Zhang Youjun (first from right), Xia Jixing (second from right), and Guo Zhao will observe the experimental conditions of Bemisia tabaci on tomatoes.
The mystery of "food habits"
The mystery of "food habits" In 1996, a pest that resembled the whitefly whitefly in a greenhouse was discovered in a vegetable greenhouse in Beijing.
It turns out that this is the pest Bemisia tabaci that has invaded our country.
"From then on, the mystery of insect feeding habits became a lingering question in my mind.
Some insects only feed on one plant, such as brown planthopper, which only eats rice, which is monophagous; some can eat multiple plants within a family or related families, such as Plutella xylostella only feeds on cruciferous vegetable crops, called widowhood.
Feeding habits are closely related to pest population outbreaks.
Feeding habits are closely related to pest population outbreaks.
Strong, how to prevent it? Feeding habits are obviously closely related to the outbreak of pests.
Secondary metabolites are important weapons for plants to resist pests, just like shields protecting plants.
"Bemisia tabaci can eat more than 600 kinds of plants, indicating that it can resist most secondary metabolites.
Polyphagy is the main cause of Bemisia tabaci outbreaks.
Polyphagy is the main cause of Bemisia tabaci outbreaks.
Photo courtesy of Vegetable Research Institute, Chinese Academy of Agricultural Sciences Bemisia tabaci not only causes direct damage by sucking the phloem sap of the host plant, but also secretes honeydew to induce plant fungal diseases such as coal pollution and damage plants.
More importantly, Bemisia tabaci can transmit more than 300 plant viruses every year.
Cause billions of dollars in economic losses.
Since 2001, the team has concentrated on the host adaptability of Bemisia tabaci and the mechanism of its outbreak.
Through the detection of more than 6000 samples from more than 260 field populations across the country and the study of allelic frequencies, differentiation coefficients and gene flow among populations, they clarified the status of the invasion and distribution of Bemisia tabaci in my country, the source of the invasion population, Diffusion path and invasion characteristics.
Through the methods of biology, ecology and molecular biology, they clarified that the spread and outbreak of invasive Bemisia tabaci populations are related to their unique biological characteristics, stronger adaptability to high temperatures and changes, and stronger host adaptability.
"These works laid the foundation for us to analyze the molecular mechanism of Bemisia tabaci to phenol sugar detoxification.
" Zhang Youjun said.
Steal the "spear" of plants
Steal the "spear" of plants Zhang Youjun’s team started with plant secondary metabolites and analyzed the metabolic profile of tomato leaves and detected 9873 compounds.
Among the 9873 compounds detected, 290 phenol sugars were identified, accounting for 2.
93%.
Phenol sugar is an important plant anti-insect secondary metabolite, mainly composed of phenol and glycosides, which can inhibit the growth and development of insects.
The amazing thing is that the phenol sugars secreted by the plants themselves are also harmful to the plants themselves.
"Too much phenol sugar is not good for plant growth and development.
" said Guo Zhaojiang, the co-first author of the paper and a researcher at the Institute of Vegetable Research.
Therefore, when the pests leave, plants will quickly degrade the excess phenol sugars.
Too many secondary metabolites are not good for plant growth and development.
Photo courtesy of Vegetable Research Institute, Chinese Academy of Agricultural Sciences
Too many secondary metabolites are not good for plant growth and development.
Photo courtesy of Vegetable Research Institute, Chinese Academy of Agricultural Sciences The "antidote" that plants prepare for themselves is phenol sugar malonyl transferase (PMaT).
The malonylation reaction of phenol sugar catalyzed by it plays an important "detoxification" effect in the life process of plants.
So, how does Bemisia tabaci, which like to eat tomato leaves, deal with phenol sugars?
The past chemical analysis can no longer answer this problem.
For a period of time, the research on the detoxification mechanism of Bemisia tabaci has been slow.
In 2009, Bemisia tabaci Q-type broke out in a large area in China and spread the virus on tomatoes, causing economic losses of more than 10 billion yuan.
The prevention and control of Bemisia tabaci is of urgency.
At this time, advances in genome sequencing technology brought hopes of breaking through the bottleneck.
Zhang Youjun's team decided to sequence the genome of the Q-type Bemisia tabaci.
In 2013, the Bemisia tabaci genome was sequenced and 20786 genes were obtained.
Yang Zezhong, the co-first author of the paper, told China Science Daily that in the process of analyzing the genes related to the complex advanced functions and biological systems of Bemisia tabaci, “we discovered the gene that was later named BtPMaT1.
I was very excited at the time.
"
Because they later proved that the Bemisia tabaci gene is homologous to the plant's phenol sugar malonyl transferase.
"The BtPMaT1 gene does exist in the Bemisia tabaci genome, not the plant genome contamination.
" Zhang Youjun said that the phylogenetic tree analysis showed that the homologous gene of the Bemisia tabaci BtPMaT1 gene only exists in plants and a small number of fungi.
"This is the gene'stolen' from the plant by Bemisia tabaci, and it is a horizontal gene transfer phenomenon that is widespread in the biological world.
" Zhang Youjun said.
Bemisia tabaci obtains PMaT1 detoxification gene from plants through horizontal gene transfer event.
Image courtesy of Vegetable Research Institute, Chinese Academy of Agricultural Sciences
Bemisia tabaci obtains PMaT1 detoxification gene from plants through horizontal gene transfer event.
Image courtesy of Vegetable Research Institute, Chinese Academy of Agricultural Sciences.
Bemisia tabaci obtains PMaT1 detoxification gene from plants through horizontal gene transfer event.
Image courtesy of Vegetable Institute, Chinese Academy of Agricultural Sciences.
Previous studies have proven that horizontal gene transfer often occurs between prokaryotes, and is generally considered to be the driving force for the evolution of prokaryotes.
More and more evidences show that horizontal gene transfer is also an important factor in the adaptive evolution of eukaryotes.
However, almost all gene donors for arthropod horizontal gene transfer events are microorganisms, and experimental evidence for horizontal transfer of plant-derived functional genes to insects has been lacking.
The co-corresponding author of the paper, chemical ecologist and entomologist Ted Turlings of the University of Neuchâtel, Switzerland, said: “This study provides the first internationally functional evidence of the horizontal transfer of plant genes to insects, which can metabolize plants.
The gene for defensive toxins-BtPMaT1 is only found in Bemisia tabaci, and it is absent in other insects.
"
The horizontally transferred gene BtPMaT1 has been detected in different cryptic species of Bemisia tabaci (different species that are difficult to distinguish, but have reproductive isolation), but not found in the genomes of other insects, including the most closely related whitefly whitefly.
The gene.
Xia Jixing said, therefore, it can be inferred that the time for the horizontal transfer of this gene should be after the differentiation of Bemisia tabaci and the greenhouse whitefly (about 86 million years ago) and before the differentiation of the cryptic species of Bemisia tabaci (about 35.
3 million years).
Before), this may explain the reason why Bemisia tabaci is more adaptable to tomato hosts than the greenhouse whitefly.
Through in vitro cell expression enzyme activity analysis, Bemisia tabaci midgut tissue enzyme activity analysis and Bemisia tabaci excreta enzyme activity metabolism analysis, it is found that this gene still performs the same function as the plant homologous gene—detoxifies phenol sugars.
"The'spear' of the plant was stolen by the whitefly, but turned into a'spear' that attacked the plant.
" Zhang Youjun said.
Bemisia tabaci uses the BtPMaT1 gene to detoxify plant phenol sugars in the midgut.
Photo courtesy of Vegetable Research Institute, Chinese Academy of Agricultural Sciences
Bemisia tabaci uses the BtPMaT1 gene to detoxify plant phenol sugars in the midgut.
Photo courtesy of the Vegetable Research Institute, Chinese Academy of Agricultural Sciences.
Bemisia tabaci uses BtPMaT1 gene to detoxify plant phenol sugars in the midgut.
Photo courtesy of the Vegetable Research Institute, Chinese Academy of Agricultural Sciences.
A professional reviewer of "Cell" magazine said: "This research represents an important advance in the field of plant-insect interaction research, expounds novel resistance mechanisms, and explains that Bemisia tabaci has amazing host adaptability to a variety of crops.
"This paper uses clever molecular genetic methods to reveal how insects use horizontal gene transfer to overcome host defenses.
"
Countermeasures with RNA interference
Countermeasures with RNA interference Countermeasures with RNA interference "We think that a certain plant virus may carry the BtPMaT1 gene.
After being fed by the whitefly, the virus integrates the gene into the whitefly's genome through an unknown mechanism.
" Turlings said, "Of course, This is a seemingly impossible thing, but imagine that in millions of years, billions of insects, viruses, and plants evolve over time.
This happens occasionally.
If the genes obtained are beneficial to insects , Then it will evolve more beneficially and spread widely.
"
After revealing the molecular mechanism of Bemisia tabaci’s incredible adaptability, Zhang Youjun’s team developed a strategy to crack the “super power” stolen by Bemisia tabaci, that is, using RNA to interfere with the BtPMaT1 gene of Bemisia tabaci to make it right This plant is sensitive to toxic compounds.
RNA interference refers to a phenomenon that is highly conserved in the evolutionary process, induced by double-stranded RNA, and homologous mRNA is efficiently and specifically degraded.
Its role is to silence related genes.
Here, "We made hairpin RNA using fragments of the BtPMaT1 gene, and fed the hairpin RNA directly to Bemisia tabaci.
The interference efficiency was about 50%.
After silencing the gene, three phenol sugar treatments would kill the whitefly.
The rate increased by about 20%.
" Zhang Youjun said.
In addition, they also constructed a genetically modified tomato line expressing the hairpin RNA.
They found that in the excreta of Bemisia tabaci eating genetically modified tomatoes, the content of some phenolic sugars increased, and the acylation products of some phenolic sugars decreased.
"Without the action of pesticides, the mortality rate of Bemisia tabaci was 15.
48% after eating wild tomatoes for 7 days, and the mortality rate of Bemisia tabaci was 93.
35% after eating transgenic tomatoes for 7 days.
However, for non-target arthropods, aphids and two-spotted spider mites No effect.
" Guo Zhaojiang said that genetically modified tomato strains can effectively control Bemisia tabaci.
Photo courtesy of Vegetable Research Institute, Chinese Academy of Agricultural Sciences
Photo courtesy of Vegetable Institute, Chinese Academy of Agricultural Sciences Photo courtesy of Vegetable Institute, Chinese Academy of Agricultural Sciences Dr.
Roy Kirsch, a researcher at the Max Planck Institute for Chemical Ecology in Germany, disclosed his identity as a professional reviewer for Cell.
He thinks this article is "very interesting" and will arouse great interest among ecologists, evolutionary biologists, phytochemists and pest controlers.
"The research covers everything from plant metabolic profiles to insect comparative genomes and everything in between, and in-depth research to solve problems from different angles.
"
"Of course, the application of this method still needs to overcome some obstacles, the most obvious is people's worries about genetically modified crops.
" Turlings said, "but in the future, I do think that this is a green, efficient and safe method for whitefly control.
Because the gene is derived from a plant, and now that we have a clear mechanism of its action, we are also able to deal with possible changes in the Bemisia tabaci gene.
"
"The gene transferred into this genetically modified tomato is a plant homologous gene, so it is more green and efficient.
It may be applied to the whitefly control process in the future.
" Zhang Youjun said that they have applied for a Chinese national invention patent.
(Source: China Science News Li Chen)
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