Cotton "cancer" or will be conquered

Chinese scientists have revealed the molecular mechanism of the leaves caused by Verticillium dahliae -

Recently, the pest prevention and control innovation team led by Dai Xiaofeng, director of the Agricultural Products Processing Research Institute of the Chinese Academy of Agricultural Sciences, discovered the molecular mechanism of the leaf caused by Verticillium dahliae, the pathogen of cotton verticillium. The results were published online on January 4, 2019 in the internationally renowned botany journal New Phytologist.

It is reported that the study will provide a theoretical basis for the molecular epidemic monitoring and forecasting of cotton and other economic crops such as Verticillium wilt (cotton "cancer"), breeding of disease-resistant varieties and development of new biocontrol agents ("Ke Xing").

According to Dai Xiaofeng, as early as 1817, German scientists discovered the first round of Verticillium dahliae, a pathogenic fungus that spreads through the soil. It can destroy the water and nutrient transport system of plants, and quickly cause the plant to yellow and wilting. It was once listed as the world's number one quarantine object with potato late blight.

In 1929, Verticillium dahliae was widely spread in the major agricultural states of the United States. In 1935, it was introduced into China by the cotton species. The rapid spread of this strain directly led to the large-scale outbreak of verticillium wilt in China from the 1990s to the beginning of this century, which caused heavy losses in cotton production.

At present, the economic losses caused by cotton each year are still more than 10 billion US dollars.

Even more frightening is that the host of Verticillium dahliae has a broad spectrum, it can infect more than 600 plants in 8 families, including potato, eggplant, pepper, lettuce, tomato, strawberry and other important cash crops, as well as peony and chrysanthemum. Chinese herbal medicines such as honeysuckle and ornamental plants, such as Xiangshan Hongye (Astragalus membranaceus), cause the annual economic loss of more than 100 billion US dollars caused by Verticillium dahliae worldwide.

For more than half a century, agricultural researchers all over the world have been working to analyze the genetic mechanism of defoliation caused by Verticillium dahliae, focusing on phenotypic identification, pathogenic differentiation, molecular evolution and genetic testing methods. A series of studies have been carried out to provide theoretical basis and technical support for the epidemic monitoring and prevention control of Verticillium dahliae, but there has been no breakthrough.

The Dai Xiaofeng team has been working on related fields since the 1990s. They used high-throughput sequencing technology to analyze the genome of Verticillium dahliae from Chinese cotton, through the genome of Verticillium dahliae from American lettuce and Dutch tomato. In comparison, it was found that the Verticillium dahliae strain had one more genomic fragment than the United States and the Netherlands, and the fragment was just "picked" (genetic level transfer) from the other pathogen of cotton, Fusarium oxysporum.

"That is to say, Verticillium dahliae obtains part of the gene fragment of Fusarium, which has a stronger ability to infect cotton." Dai Xiaofeng said.

As the research progressed further, the team found that the “grab” gene fragment contained seven genes (called VdDf1 to VdDf7). Dai Xiaofeng visually referred to them as a “small team”. In this team, each “team member” performs his or her duties. Some of them are responsible for transcriptional regulation factors, and some are responsible for encoding transporters. Among them, the two most critical "members" are responsible for encoding polyketide synthase (VdDf5 and VdDf6), which is a key functional gene that causes host defoliation.

"VdDf5 and VdDf6 are the core figures of this team. Without them, the team will not be able to operate normally." Dai Xiaofeng pointed out.

When this genomic fragment is obtained by Verticillium dahliae, the encoded functional gene is directly involved in the synthesis and transport of the defoliating compound (N-acylethanolamine). On the one hand, this compound interferes with the phospholipid metabolic pathway in cotton, making cotton more sensitive to a plant endogenous hormone called "abscisic acid"; on the other hand, it plays a similar role to abscisic acid, making the endogenous hormone of cotton The system is disordered, and the excessive synthesis of abscisic acid is abnormal, which eventually causes the cotton leaves to fall off.

According to reports, in recent years, with the support of the national agricultural science and technology innovation project, the team has been running from Europe and the United States five years ago in the fields of the mechanism of disease damage and the molecular mechanism of disease resistance. . This study will provide a solid theoretical basis for the future development of defoliation-type pathogen molecular surveillance, breeding of disease-resistant varieties and development of new biocontrol agents.

It is reported that the Dai Xiaofeng team is currently leading the organization of the “International Science Program for the Research of Verticillium Daphylococcal Genomics” by 14 leading units at home and abroad. It is expected to be more systematic in the future from the perspective of genome-wide, metabolomics and synthetic biology. To clarify the origins, population structure and genetic evolution of the global verticillium wilt disease, which have plagued the international academic community for hundreds of years.