Transforming amber waves of grain: New genome assembly for 'Fielder'
wheat cultivar
Scientists use new technology to assemble a high-quality genome sequence
of a common wheat cultivar often used for genetic modification

Date:
August 2, 2021
Source:
Okayama University
Summary:
Researchers 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. The development has important
implications for wheat genome- editing research and agriculture.



FULL STORY ========================================================================== 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." ========================================================================== Story Source: Materials provided by Okayama_University. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Kazuhiro Sato, Fumitaka Abe, Martin Mascher, Georg Haberer, Heidrun
Gundlach, Manuel Spannagl, Kenta Shirasawa, Sachiko
Isobe. Chromosome- scale genome assembly of the
transformation-amenable common wheat cultivar 'Fielder'. DNA
Research, 2021; 28 (3) DOI: 10.1093/dnares/ dsab008 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/07/210730104311.htm

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