For the first time in history, researchers have successfully edited mitochondrial plant DNA in a move that has significant positive repercussions for future food security.
Found in mitochondria, the part of the cell responsible for converting energy into a fuel source, mitochondrial DNA is one of a number of DNA types found in animals and plants.
However, due to the industrialised nature of modern farming, the diversity of mitochondrial DNA in most crops is extremely poor.
This means that it is a significant weak point within the food supply, as a disease targeting the mitochondrial DNA has the potential to wipe out large portions of a given crop in a short period of time.
This has already happened. In 1970, for example, 15% of the American corn crop was killed in a single year due to a fungal infection targeting a gene found in the mitochondrial DNA of all corn in Texas.
By successfully editing mitochondrial plant DNA for the first time, researchers have created the possibility for crops to be engineered to have far greater genetic diversity, building increased resistance to potential disease.
Plant DNA editing a historic achievement
The feat was achieved by scientists at the University of Tokyo in Japan, and represents a dramatic breakthrough for the field.
While animal mitochondrial DNA was successfully edited in 2008, this is the first time the feat has been achieved in plants. It follows the successful editing of chloroplast DNA in 1988 and nuclear DNA in the 1980s.
The reason mitochondrial plant DNA editing has taken so much longer than for animals is that in plants this area of the cell is much more complicated. While in animals the mitochondrial genome is a small molecule that is very similar in all species, in plants it large and varied.
“The plant mitochondrial genome is huge in comparison,” explained Associate Professor Shin-ichi Arimura, from the University of Tokyo.
“The structure is much more complicated, the genes are sometimes duplicated, the gene expression mechanisms are not well-understood, and some mitochondria have no genomes at all – in our previous studies, we observed that they fuse with other mitochondria to exchange protein products and then separate again.”
The researchers adapted a gene editing technique known as mitoTALENs, which has previously been applied to animal mitochondrial DNA. This allowed them to cut the DNA at a specific gene and delete it.
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The plant DNA editing project focused on rice and rapeseed plants with an issue known as cytoplasmic male sterility (CMS), which makes male plants infertile. Plants with CMS are successfully grown commercially, but are genetically extremely similar, putting them at risk of disease.
“While deleting most genes creates problems, deleting a CMS gene solves a problem for plants. Without the CMS gene, plants are fertile again,” said Arimura.
The plant DNA editing was successful, allowing the researchers to produce three new lines of rapeseed and four of rice.
The research, which is published today in the journal Nature Plants, will now be expanded upon to determine how best it can be used to improve food security.
“This is an important first step for plant mitochondrial research,” said Arimura.
“We still have a big risk now because there are so few plant mitochondrial genomes used in the world. I would like to use our ability to manipulate plant mitochondrial DNA to add diversity.”