The Van Trump Report

Gene Discovery Paves Way for Crop Breeding Innovations

Hundreds of plant species have a trait that allows them to form seeds without fertilization. Called “apomixis,” these plants clonally form seeds that are exactly the same genetic make-up as the mother plant that produces them. The potential benefit of this phenomenon for agriculture has long been recognized as it allows easy propagation of high yielding hybrids, but there has been limited understanding of the genes that control apomixis. Now, researchers say they’ve identified a DNA region in dandelions that is essential for the process.

Working in dandelions, plant reproductive biologists from KeyGene and Wageningen University & Research (WUR), in collaboration with colleagues from the Japanese breeding company Takii, say they’ve identified a gene that triggers parthenogenesis, which is the process whereby egg cells grow into plant embryos without fertilization of the egg cells. When they added the gene, named PAR, to a usually sexually reproducing lettuce, the plant successfully formed embryos without fertilization.

Unlocking the secrets of apomixis could accelerate the breeding of crops, make seed production less costly, and bring the advantages of hybrid breeding to many more of the world’s crop species. “Apomixis in crops could be used as a universal plant breeding tool. It would affect many crops and many traits, especially very complex traits such as yield, flavor, and taste,” explains Dr. Peter van Dijk, researcher at KeyGene and lead author of the new research paper, which is available HERE.

This is not the first parthenogenesis gene identified in plants. In 2016, the KeyGene team discover the gene for diplospory, the DIP gene, which is the first of the 2 steps involved in apomixis. The DIP gene ensures that the number of chromosomes is not halved during the formation of egg cells. The other crucial step in apomixis is that an egg cell with a normal number of chromosomes starts dividing without fertilization and grows into an embryo, aka parthenogenesis.

The researchers say that while most plants do not use apomixis, most do have genes that are strikingly similar to the PAR gene as well as the earlier found DIP gene of dandelion. This suggests that apomixis naturally acts as a modification of normal sexual reproduction and, therefore, potentially also that apomixis could be widely applicable by using modern tools like gene editing.
It is important to note that the embryos in the PAR experiment did not form viable seeds and the researchers are not exactly sure why. In their new publication, the research team speculates that the embryos were not nourished properly. Venkatesan Sundaresan, a plant biologist at UC Davis, theorizes that the PAR gene may not be the only one necessary for apomixis.

Eric Schranz, a plant scientist at Wageningen University and paper coauthor, says more research is needed. “It’s not automatic that a system will work in one species or another,” he says. “Every plant is going to have some slight details where you have to tweak it. And that whole tweaking per crop might take quite some time.”

Still, finding another gene linked to parthenogenesis is important for further research on apomixis and for the future application of apomixis to crops. For now, the most practical application of the new knowledge could be inducing parthenogenesis to produce genetically identical plant tissue for lab experiments, suggests Schranz. That could reduce the time it takes for plant researchers to grow tissue culture in a petri dish. “It’s really difficult to set up a new tissue culture pipeline, and people can lose six months of their PhD trying to figure it out,” he says. (Sources: PhysOrg, SeedWorld, PNAS, AllAboutFeed)

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