Yesterday, the online edition of the journal Nature reported on the results of Gao Caixia's group at the Institute of Genetics and Developmental Biology of the Chinese Academy of Sciences and Qiu Jinlong's research group at the Institute of Microbiology, who developed a new wheat mutant, Tamlo-R32, which has strong resistance to powdery mildew without any yield defects.
Tamlo-R32 mutant (medium) has powdery mildew resistance and no growth defects | References[3]
This achievement marks an important theoretical and technological breakthrough in the way disease-susceptible genes are used to cultivate disease-resistant plants. It means that powdery mildew, which is known as one of the three major diseases of wheat, has finally been "taken down" by mainland scientists. The findings were published in Nature on February 9, 2022 under the title Genome-edited powdery mildew resistance in wheat without growth penalties.
"This research work, which has important theoretical and practical application value, will become a landmark achievement in the field of crop breeding." Academician Kang Zhensheng of Northwest A&F University commented on this. This achievement demonstrates the great potential of genome editing in the molecular design and breeding of crops, which is of great significance for ensuring food security.
After 8 years,
Obtain disease-resistant mutants that grow well
Wheat is the world's staple food crop and feeds more than a third of the world's population. Powdery mildew is one of the main diseases affecting wheat yields. In the 1980s, scientists have found barley that is resistant to powdery mildew. The loss of MLO pathogenetic gene function has given barley broad-spectrum disease resistance, which has been introduced into barley varieties, but it is very difficult to make wheat disease resistant.
Wheat is the main food crop around the world, but it is difficult to make wheat disease resistant | Pixabay
Pathogens typically utilize the disease-susceptible genes of the plant host to achieve successful infection. Although mutations in the susceptible gene can lead to broad-spectrum, long-lasting resistance to pathogenic bacteria, knockout of the susceptible gene usually leads to pleiotropy, which greatly limits its application in disease resistance breeding.
As early as 2014, Gao Caixia and Qiu Jinlong's team used genome editing technology to knock out the MLO gene in the three genomes of A, B and D at the same time in hexaploid wheat, and obtained Tamlo, a broad-spectrum high powdery mildew resistant hexaploid wheat material, which was published in Nature Biotechnology. This is a classic case of gene-edited breeding.
The 2014 article attracted worldwide attention, was selected as one of the 20 most influential articles in the 20th anniversary of Nature Biotechnology, and was praised by MIT Science and Technology Review as "one of the world's top ten technological breakthroughs". Professor Gao Caixia also led the wave of plant genome editing and was selected as one of the "Ten Chinese Science Stars" in 2016 by Nature.
Although this variant shows strong disease resistance, it yields poorly compared to wild-type wheat. In the follow-up screening, the researchers found a new MLO mutant, Tamlo-R32, which showed disease resistance while showing plant height and growth conditions were better than other mutants, no different from wild-type wheat. Taking this as a breakthrough point, after 8 years of research, we have finally cultivated excellent wheat varieties with powdery mildew resistance and no growth defects.
Break through many scientific research difficulties
However, it is not easy to breed a "perfect" good wheat variety. The ordinary wheat genome is very large, 5 times the human genome and 40 times the rice genome, and its sequence repeatability is also very high, and the genome structure is extremely complex. Limited by the genomic data at the time, the research team explored the problem for four years.
Until 2018, the newly completed wheat genome resequencing data and chromosome fine maps brought progress to the research.
A section of the Tamlo-R32 mutant is missing a gene up to 304 kilobase pairs | References[3]
The researchers found that the Tamlo-R32 mutant had a deletion of up to 304 kilobase pairs near TaMLO-B1 in addition to two premature termination codons at the TaMLO-A1 and TaMLO-D1 sites. RNA sequencing showed that this large number of deletions altered the local chromatin status, resulting in ectopic activation of TaTMT3B.
Wild-type (left) TaTMT3 expression is inhibited; after the Tamlo-R32 mutant (right) deletes the 304Kb large-fragment genome, TaTMT3 expression is activated | References[3]
The researchers then determined the positive effect of TaTMT3B on restoring wheat growth and yield after MLO disease gene knockout. The researchers further found that overexpression of TMT3 in the model plant Arabidopsis thaliana also overcame the negative phenotype produced by mutations in its disease-inducing genes. This shows its potential for application in a wide range of crops.
In order to expand the application of its research results in crop disease resistance breeding, the researchers used traditional breeding methods to cross Tamlo-R32 mutants with excellent wheat varieties, successfully introducing excellent disease resistance traits into excellent varieties.
In order to complete this task more efficiently, the researchers used a simple and rapid method, using multiplexed CRISPR technology, directly on the excellent wheat varieties to make a directional breakthrough, and it only takes 2-3 months to successfully create excellent wheat varieties with both broad-spectrum powdery mildew resistance and high yield.
Gao Caixia | China Science Network
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[1]https://news.sciencenet.cn/htmlnews/2022/2/473719.shtm
[2]https://www.eurekalert.org/news-releases/942549
Author: Small pot
Edit: Crispy fish
Typography: Yin Ningliu
Team information
Co-Corresponding Authors:
Gao Caixia: Researcher of the Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Bachelor of Gansu Agricultural University in 1991, Master of Gansu Agricultural University in 1994, Ph.D. of China Agricultural University in 1997, Postdoctoral Fellow of DLF-Trifolium Research Department of Denmark from 1997-1998, Research Scientist, Research Department of DLF-Trifolium Company, Denmark from 1998 to 2009. In September 2009, he returned to China and served as a researcher and leader of the research group at the State Key Laboratory of Plant Cell and Chromosome Engineering of the Institute of Genetic Development, and was selected as an "Outstanding Technical Talent" of the Chinese Academy of Sciences in 2010. His main research areas are plant genome editing technology, biosafety new breeding technology and genome editing directed design molecular breeding, and is committed to promoting the application of genome editing in molecular design breeding.