Investigate Which Genes Drive This Variation

Next, they wanted to investigate which genes drive this variation. The researchers performed genome-wide association studies (GWAS) on a subset of the plants that they had characterized. They chose two species, H. annus and H. petiolaris. In H. annus alone, the researchers found a single nucleotide polymorphism (SNP) that was responsible for 62 percent of the variation in floral UV patterns. H. petiolaris didn’t yield such clean results. They detected several genomic regions associated with bullseye size in H. petiolaris subspecies H. petiolaris petiolaris but found no genomic regions associated with bullseye size in subspecies H. petiolaris fallax.

“Finding a single region in the genome that explained so much variation was pretty amazing,” Matthew Koski, a plant biologist at Clemson University who was not involved in the study, tells The Scientist. Koski studies the UV pigmentation of cinquefoil, a flowering plant.

The Influential SNP Is a Transcription Factor Called HaMYB111

In H. annus, the influential SNP is in a transcription factor called HaMYB111, which controls the production of flavonol glycosides. These compounds can absorb UV but also have other key functions, including water retention, limiting transpiration, and reducing damage from oxidative stress. In that way, the connection between the UV patterns and reducing water loss made sense—larger patterns would occur when the plant is pumping out lots of moisture-retaining flavonol glycosides. Still, to be certain of the transcription factor’s influence on petal coloration, the researchers engineered the gene into Arabidopsis thaliana mutants, which lack UV bullseyes. The engineered plants gained bullseyes, showing that HaMYB111 is indeed responsible for producing the bullseye-making glycosides.

“This was an amazing combination of multiple interesting approaches to understanding both the genetic underpinnings of floral pigmentation and the potential adaptive roles,” says Koski, “and in the end, it came together as a really beautiful biological story.”

He says the findings could “absolutely apply to other flowers,” adding that this study and studies like it can potentially give researchers a peek at how plants may respond to climate change. “From a global change standpoint, some regions are going to be experiencing increased aridity, some regions are going to be experiencing decreased aridity, more rainfall. This study might help project how these traits might respond to changes in environmental conditions.”

John Burke, a plant geneticist at the University of Georgia who was not involved in the study but who has previously collaborated with the authors of the paper, agrees. “This is a single trait that potentially influences the sunflowers’ ability to survive or thrive in a given environment. That could have implications for defining range limits of wild species and predicting impacts as the environment is changing,” he says.

Todesco says he hopes the findings will help farmers. Sunflowers are cultivated for various reasons, including sunflower oil, which is a $20 billion industry. Global climate change, he says, will likely disrupt this industry. Studies like this one are important, he adds, because “understanding how crops have [adapted] in the past can provide information on how to make these crops more resilient to what is coming, which is a disruption of agriculture and plants as we know them.” lavenderblueflowers


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