Release Subtitle:
Scientists use new technology to assemble a high-quality genome sequence
of a common wheat cultivar often used for genetic modification
Release Summary Text:
Genetically modified crops are said to be the solution to the daunting
issue of world hunger. Dr. Kazuhiro Sato of Okayama University and his
colleagues have established an accurate genome assembly of ‘Fielder’
wheat, which—unlike other wheat cultivars—is very amenable to genetic
editing through bacterial transformation. This genome sequence was
generated using a technique that is easier than previous sequencing
methods. This development has important implications for wheat
genome-editing research and agriculture.
Full text of release:
Wheat is a staple in the diets of numerous cultures. Increasing wheat
production efficiency would help feed more people and reduce associated
agricultural costs. Genetic engineering has the potential to generate
better wheat cultivars with characteristics we desire, but
unfortunately, wheat is also one of the hardest crops to genetically
modify. This is because wheat is resistant to “transformation,” the
process of introducing new genes into cells so that they are
incorporated into the genome and passed down to the next generation,
even with the development of a successful plant transformation system
that uses Agrobacterium tumefaciens.
The wheat cultivar that is easiest to transform is ‘Fielder,’ developed
in the 1970s by the University of Idaho, but scientists do not know why
this particular cultivar is so amenable to transformation when others
are not. Additionally, difficulties in transforming other wheat
cultivars limit the genetic enhancements that can be performed on this
key crop. Not ones to back away from a challenge, a group of scientists,
led by Dr. Kazuhiro Sato of Okayama University’s Institute of Plant
Science and Resources, has assembled the ‘Fielder’ genome, and spatially
arrange them into chromosomes.
A better understanding of wheat genomes is one step to addressing this
problem, and scientists are hard at work uncovering the genetic sequence
of wheat. In fact, in a massive project published in 2020, scientists
sequenced as much as they could of entire genomes from 10 wheat
cultivars. However, sequencing technology is constantly advancing, and a
study published this year found that a process called circular
consensus sequencing (CCS) can quickly and accurately read long sections
of the barley genome, capturing the full sequence of most genes.
“The CCS technique can fill in any sequencing gaps from earlier
sequencing efforts, while also being simpler and reasonably
cost-effective. So, we figured that CCS would work for wheat as well as
barley and went ahead to use it successfully. Our work here represents
the next standard in wheat genome sequencing analysis,” Dr. Sato
explained. Their findings in their entirety are published in DNA
Research.
After sequencing the ‘Fielder’ genome using CCS, the researchers used
another technique called high-throughput chromosome conformation capture
to organize the sequences into individual chromosomes. The team was
compared their results to previously published genomes and drew several
important conclusions. First, their CCS-generated genome matched
previous genomes in structure and quality but is less complex to
perform. Second, ‘Fielder’ does not have an unusual gene set compared
with the 10 wheat cultivars of the 2020 study. Third, comparisons with
sequences from a previously created mutant wheat plant indicated that
the CCS-generated genome is useful for verifying the success of earlier
genome-editing efforts. For example, the team was able to confirm four
regions of transgene insertion into the mutant wheat. They were also
able to find regions that are candidates for off-target mutations, which
are instances where genetic modification occurs in unintended locations
of the genome. This discovery clearly benefits future efforts to reduce
off-target effects during genome editing.
When asked to discuss the implications of their research, Dr. Sato
commented, “Many countries, including the United States and Japan, are
looking seriously into breeding genetically modified wheat to improve
crop productivity. We demonstrated here that the CCS technique is
effective on the highly complex wheat genome, and we hope this will
encourage more researchers to analyze wheat haplotypes that they are
targeting for genetic engineering. Also, the high-quality genome
sequence we generated is necessary for improving the efficiency of
genome editing in ‘Fielder’ and to demonstrate that any new
modifications are safe for human consumption—without any undesired
mutations somewhere we didn’t expect.”
Release URL:
https://www.eurekalert.org/news-releases/923974
Reference:
Chromosome-scale genome assembly of the transformation-amenable common wheat cultivar ‘Fielder’
Journal: DNA Research
DOI:10.1093/dnares/dsab008
Contact Person: Kazuhiro Sato
Dr. Kazuhiro Sato is affiliated with the Institute of Plant Science and
Resources, as well as the Barley Germplasm Center (Institute of Plant
Science and Resources), at Okayama University in Kurashiki, Japan. He is
an author on over 100 articles in a career that has spanned three
decades. Dr. Sato’s areas of interest include plant biotechnology,
molecular biology, and genetics, most notably of major crops such as
barley, wheat, and rice.
https://www.okayama-u.ac.jp/eng/research_highlights/index_id140.html
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