The innovation team of vegetable germplasm resources of the Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences established an accelerated evolution model of polyploid plants

Distal hybridization and polyploidization are the main drivers of the explosion of
angiosperm species.
More than half of the world's crops and their wild relatives have undergone distant hybridization and genome doubling
.
The degree of genome rearrangement varies greatly
across taxa.
The molecular mechanisms that cause this phenomenon have always been major scientific questions
in biology.
Although some genomic evolution theories have been proposed through genomic analysis of existing species, experimental verification
is lacking.
Therefore, it is important
to create a research model for the accelerated evolution of the genome.

 

Recently, the germplasm resource team of the Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, established a research model of accelerated genome evolution in synthetic radish × cabbage (RRCC) heterotetraploid, revealing the early evolutionary characteristics of heteropolyploid plant genomes, promoting progenitor chromosome recombination and chromosome culling through gene editing, and inducing for the first time secondary meiosis
that can rapidly double gametes.
At the same time, the gene fixed-point conversion was realized at the fine site, and a new gene
chimeric at the target site was created.
The artificial polyploid evolution model created by this study provides a key platform
for genetic research and breeding.
The developed chromosomal recombination technology, gene fixed-point conversion and new gene induction technology provide important tools
for crop gene design.
The related research results were published on December 30, 2022 under the title Characterization and acceleration of genome shuffling and ploidy reduction in synthetic allopolyploids by genome sequencing and editing The article was published in Nucleic Acids Research
.

 

The cruciferous family contains important vegetable crops such as radish, cabbage, kale, rape, mustard greens and other important vegetable crops, oil crops and seasoning crops
.
Distant-range hybridization is widely used in germplasm innovation and genetic breeding of cruciferous crops
.
Radish and brassica crops independently evolved each other's scarce excellent traits and resistance genes
.
However, the difficulty of recombination of the genome between genera restricts the shuttle transfer of excellent genes, which makes it difficult for distant hybrid breeding to make substantial breakthroughs
.
In order to solve this problem, the research team created and introduced a large number of new germplasms
of distant hybrids in the early stage.
The study first sequenced a self-inflicted radish × cabbage (RRCC) heterotetraploid genome, revealing the early evolution of the polyploid genome
.
It was found that genomes in synthetic heteropolyploidy were deleted quickly, while genome rearrangements were much
slower.
Core and high-frequency genes tend to be retained, while endemic and low-frequency genes tend to be lost
.
Large fragments of chromosomal deletions are enriched in heterochromatin regions, possibly resulting from
chromosomal breaks.
Transposation between genomes occurs mainly between homologous fragments, mainly short fragments
.
It was shown that gene conversion is the main way
of genetic material transfer between distant hybrid genomes.
In order to accelerate genome rearrangement, efficient gene editing technology
was established on radish × kale.
By editing the FANCM gene, the recombination efficiency of some homologous (also translated as homoeologous) chromosomes was improved, and for the first time, secondary meiosis
that can rapidly double the gamete genome was induced.
Genomic downdoubling has important application value
in distant hybridization and ploidy breeding.
By editing the FLIP gene, the gene was successfully converted and a new gene
was chimeric at the target site.
The results reveal the evolution law of the newly synthesized heteropolyploid genome, establish a research model for accelerated genome recombination, efficient culling, and rapid doubling for the first time, and create a technology
for precise conversion of homologous genes to create new genes.
The results have broad application prospects
in the fields of polyploid artificial evolution, germplasm resource innovation and genetic breeding.

 

Current breeding faces severe resource constraints and technical bottlenecks
.
If each gene is compared to a card, then a good variety or an excellent backbone parent is a good card that breeders are lucky enough to catch, and its formation and acquisition have a strong contingency
.
The results of this research give breeders the initiative to shuffle, divide and change cards
.
Therefore, this revolutionary new technology will break through the constraints of kinship on the availability of germplasm resources, and create new varieties, new materials and new genes
with distant advantages.

 

The first authors of the paper are Zhang Xiaohui, associate researcher of the Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, and his master's students Zhang Shuangshuang and Liu Zhongping
.
The corresponding authors are Associate Professor Zhang Xiaohui and Professor
Wang Haiping.
The paper especially acknowledges the contribution of researcher Li Xixiang
.
The research was supported
by the National Natural Science Foundation of China, the Innovation Project of the Chinese Academy of Agricultural Sciences and the Institute-level Young Talents.

 

Original link: https://academic.
oup.
com/nar/advance-article/doi/10.
1093/nar/gkac1209/6965464