Golden combination digs deep into new maize genes to help germplasm improvement

Golden combination digs deep into new maize genes to help germplasm improvement

Gold combination digs deep into new maize genes to help germplasm improvement Gold combination digs deep into new maize genes to help germplasm improvement

Controlled pollination of the EMS chemical mutant library of RP125
.

Photo courtesy of the interviewee

Controlled pollination of the EMS chemical mutant library of RP125

On July 13, " The Plant Journal " ( The Plant Journal ) published online the latest results of the collaborative research of multiple teams
.

They assembled the first high-quality reference genome of maize inbred lines in China from scratch, and created a mutant library with rich phenotypic variation in this context

The Plant Journal

High-quality assembly of the first domestic excellent inbred line genome

High-quality assembly of the first domestic excellent inbred line genome

Maize is one of the most important crops in the world.

In the process of adapting to different habitats, a wide variety of maize inbred lines have been produced

"Because of the rich genetic diversity of maize, accurate genome and annotation information is the basis for crop improvement and accurate identification of the whole genome
.

" Zhang Zhiming, a professor at Shandong Agricultural University and co-corresponding author of the paper, told the Chinese Journal of Science that since 2009 Since the release of the reference genome of B73, several other important inbred lines in North America, South America and Europe have been sequenced and assembled, but only a few inbred lines in China have genome information

"Many of the excellent breeding lines widely used in China and Asia do not have high-quality genome information
.

" said Wu Qingyu, the co-corresponding author of the paper and a researcher at the Institute of Agricultural Resources and Agricultural Regional Planning of the Chinese Academy of Agricultural Sciences.

Xu Fang, the co-corresponding author of the paper and a professor at Shandong University, told China Science Daily that the inbred line RP125 was selected by the academician of the Chinese Academy of Engineering, professor Rong Tingzhao of the Maize Research Institute of Sichuan Agricultural University , and professor Pan Guangtang of the institute.
It is a maize producing area in southwest China.
The backbone inbred line is derived from the genetic recombination progeny of the sterile strain isolated from the population of Chuandan 9 after space mutagenesis and multiple hybrids
.

professor

Xu Fang introduced that RP125 is widely adapted to different ecological regions.
Its male and female flowers can develop simultaneously at different latitudes.
The developed root system can effectively use soil fertility, and the yield can reach about 7500 kg per hectare.
At the same time, RP125 resists corn leaf spot, A variety of pathogens including head smut and bacterial wilt
.

Moreover, using RP125 as the parent, 5 hybrids with excellent traits have been bred

Therefore, the team performed de novo assembly, functional annotation, and sequence alignment on the reference genome of the maize inbred line RP125.
After revision and a series of quality inspections, the assembly quality was excellent
.

A total of 43,098 high-confidence protein-coding genes were obtained, of which 42,930 (99.

Zhang Zhiming said that the overall comparison of the RP125 genome with the genomes of inbred lines such as B73, W22 and Mo17 revealed a large number of single nucleotide polymorphisms and structural variations, but there is good collinearity between the genomes as a whole, indicating that RP125 is inbred with other inbreds.
There are large genetic differences between lines, but the overall genetic stability is stable
.

"This is the first domestic maize inbred line high-quality genome map assembled from scratch in China, which will provide valuable resources for crop improvement and accurate identification of the whole genome
.

" Zhang Zhiming said
.

Creation of mutant library under the same genetic background

Creation of mutant library under the same genetic background

The creation process and phenotype classification of RP125 maize mutant library
.
Photo courtesy of the interviewee

The creation process and phenotype classification of RP125 maize mutant library
.
Photo courtesy of the interviewee

With a high-quality genome map, in genetic research, in order to obtain the function of a gene or locus, scientists will mutate the gene or locus to form a mutant
.
"The creation, identification and application of mutant germplasm resources are the basis for the mining and genetic analysis of maize functional genes
.
" Zhang Zhiming said
.

The mutant is relative to the wild type
.
Wild corn contains more than 40,000 genes, and any mutation of any gene can become a mutant
.

At present, scientists mainly use several methods to create mutants, including EMS chemical mutagenesis, Mu transposon insertion, and CRISPR/Cas gene editing
.
Each method can create many mutants, and these mutants form a mutant library
.
For example, the chemical mutagenesis mutant library created with the B73 inbred line as the background, the transposon insertion mutant library with the W22 inbred line as the background, and the gene editing mutant library with the KN5585 inbred line as the background
.

"These mutant libraries will greatly promote the research of maize functional genes and molecular genetics
.
" Zhang Zhiming said that the collection of a large number of maize mutants will facilitate the cloning of new genes and accelerate the biological research of maize
.
Due to the huge differences in the genomes of different maize varieties, the penetration of the mutant phenotype may be affected, and the mutant phenotype may be masked under the genetic background of some inbred lines.
Construction of mutant libraries of different excellent inbred lines Still very necessary
.

"China's inbred lines are still very different from those abroad
.
Our country's own inbred lines should be assembled from scratch
.
" Xu Fang said
.
In this study, they used chemical mutagenesis methods and created 5818 mutant materials to form a mutant library
.

Xu Fang said that since not every gene mutation will lead to an obvious phenotype, they screened and identified 946 mutant materials with obvious phenotypic variation and stable inheritance, and based on the grain size, grain filling, plant height, There are 20 phenotypic classifications including disease-like spots, leaf color, grain color, ear type and leaf type
.

Wu Qingyu told the Chinese Journal of Science that the chemical mutant library has the advantages of simple creation, low cost, and high mutagenesis efficiency.
It has a wide range of application potential and is a method with the lowest threshold for creating mutants
.

Golden combination: high-quality genome and mutant library

Golden combination: high-quality genome and mutant library

"Combining the high-quality genome of the inbred line RP125 with the mutant library under the same genetic background is of great significance for mining new functional genes and isolating ideal allelic variants, enriching the genetic diversity of maize and promoting the breeding process.

"Wu Qingyu said that the golden combination of high-quality genomes and mutant libraries is very conducive to the cloning and identification of new genes
.

Wu Qingyu made a metaphor to the China Science Journal that there are a lot of gene treasures in the mutant library, and the process of locating genes is like finding a needle in a haystack
.
The high-quality maize genome is equivalent to providing a high-precision map that can help scientists quickly locate the location of the treasure gene
.

Combined with the high-quality reference genome sequence of RP125, they successfully identified 10 allelic mutations from the mutant library, of which 9 were allelic mutations of published classic mutants, but the types of mutations were different from those previously discovered
.

Clone from the mutant library to different allelic mutations of known genes
.
Photo courtesy of the interviewee

Clone from the mutant library to different allelic mutations of known genes
.
Photo courtesy of the interviewee

"One of the genes is a new gene QK1 that regulates grain filling
.
" Wu Qingyu introduced.
They found that QK1 is a recessive single gene located on chromosome 2.
After the mutation, the starch in a specific part of the endosperm is missing, the starch content is reduced, and the endosperm structure is loose.
Phenotype
.
After the mutation of this gene, it was found that the accumulation of iron and reactive oxygen in the endosperm and the mitochondria showed the characteristics of iron death.
It is speculated that excessive iron may cause the destruction of cell ion balance, which in turn affects grain development and filling defects
.

"This is a new gene that regulates grain development and grain filling.
It initially reveals a new regulation method that is different from the known regulation mode of grain filling.
It provides the first evidence that the metal tolerance protein MTP is involved in corn grain filling.
It is clear that iron plays an important regulatory role in grain development and grain filling
.
" said Wu Qingyu
.

Seed phenotype of qk1 mutant
.
Photo courtesy of the interviewee

Seed phenotype of qk1 mutant
.
Photo courtesy of the interviewee

"The RP125 mutant library we created is rich in phenotypic variation and is a valuable germplasm resource for basic maize biology research and breeding practice
.
In addition, the genetic background of the mutant library-the inbred line RP125, has wide ecological adaptability, The characteristics of disease resistance and stress resistance are good for scientific researchers in different regions to carry out research.
Under this background, they can show phenotypes that are not found in other inbred lines, which is conducive to the discovery and research of new genes
.
At the same time, mutations The excellent allelic variation of some traits in the body bank also provides important germplasm resources for maize genetic improvement and new variety breeding
.
" Zhang Zhiming said
.

This research was funded by the National Transgenic Major Project, the National Natural Science Foundation of China, the Taishan Scholars Program of Shandong Province, the Natural Science Foundation of Shandong Province, and the Innovation Project of the Chinese Academy of Agricultural Sciences
.

Genome resources are published in NCBI (PRJNA598426) and the Big Data Center of Beijing Institute of Genomics, Chinese Academy of Sciences (PRJCA002331, GWHACCD00000000)
.
Mutant resources are published at http://emsdb.
sdau.
edu.
cn (Source: China Science News Li Chen)

Related paper information: https://doi.
org/10.
1111/tpj.
15421

https://doi.
org/10.
1111/tpj.
15421