No other animals are known to make the potent antioxidants. Until now scientists thought the only way animals could obtain the orangey-red compounds was from their diet.
"It is written everywhere that animals do not make carotenoids," said Nancy Moran, leader of the UA team that overturned the conventional wisdom.
Carotenoids are building blocks for molecules crucial for vision, healthy skin, bone growth and other key physiological functions. Beta-carotene, the pigment that makes carrots orange, is the building block for Vitamin A.
"Once you start realizing how widespread carotenoids are, you realize that they're everywhere in life," said Moran, a UA Regents' Professor of ecology and evolutionary biology.
"The yellow color in egg yolks, the pink in shrimp and salmon, the pink in flamingos, tomatoes, carrots, peppers, Mexican poppies, marigolds - the yellow, orange, and red are all carotenoids."
Moran and her co-author Tyler Jarvik also figured out how the aphids they studied, known as pea aphids, acquired the ability to make carotenoids.
"What happened is a fungal gene got into an aphid and was copied," Moran said. She added that, although gene transfers between microorganisms are common, finding a functional fungus gene as part of an animal's DNA is a first."Animals have a lot of requirements that reflect ancestral gene loss. This is why we require so many amino acids and vitamins in the diet," she said.
"Until now it has been thought that there is simply no way to regain these lost capabilities. But this case in aphids shows that it is indeed possible to acquire the capacity to make needed compounds.
"Possibly this will be an extraordinarily rare case. But so far in genomic studies, a single initial case usually turns out to be only an example of something more widespread."
She and Jarvik, a research specialist in UA's department of chemistry and biochemistry, report their discovery in the paper, "Lateral Transfer of Genes from Fungi Underlies Carotenoid Production in Aphids," to be published in the April 30 issue of the journal Science. The National Science Foundation funded the research.
A lucky accident in the lab plus the recent sequencing of the pea aphid genome made the discovery possible, Moran said.
Pea aphids, known to scientists as Acyrthosiphon pisum, are either red or green. Aphids are clonal - the mothers give birth to daughters that are genetically identical to their mothers. So when an aphid in the Moran lab's red 5A strain began giving birth to yellowish-green babies, Moran and her colleagues knew they were looking at the results of a mutation.
"We named it 5AY for yellowish," she said. "That yellowish mutant happened in 2007. We just kept the strain as a sort of pet in the lab. I figured that one day we'd figure out how that happened."
Symbiotic bacteria live within aphids in specialized cells. The bacteria, which are passed from mother to babies, supply the insects with crucial nutrition. If their bacteria die, the aphids die.
Moran, who has been studying the pea aphid-bacteria system for decades, already knew the three main species of symbiotic bacteria did not make carotenoids.
She also was pretty sure the aphids didn't get their carotenoids from their diet. Aphids eat by sucking the phloem sap from plants, but the sap is carotenoid-poor. In addition, the carotenoids in the aphids were different from those usually found in plants.
In late 2009, after the complete DNA sequence of the pea aphid became available to researchers, she decided to search it for carotenoid genes.
All organisms use the same biosynthetic pathway to make carotenoids, which made searching for carotenoid genes straightforward, she said.
Lucky for Moran, the researchers who sequenced the pea aphid genome used red aphids, which have an extra copy of the carotenoid gene, making the gene causing the red color easier to find.
Next, she figured out whether the genes were from pea aphid DNA or from uncommon symbiotic bacteria or were just contamination from fungi in the sample.
In the laboratory, Moran and Jarvik found eliminating the symbiotic bacteria from a strain of aphids did not change the color of the offspring, meaning the symbiotic bacteria were not the source of the red color.
In addition, tracing the lineages of the red, green and yellow strains of aphids showed the colors had a Mendelian inheritance pattern, indicating the DNA that coded for red was part of the aphid's DNA.
That inheritance pattern also fit with another team's research that suggested both colors were present in nature because red aphids are more susceptible to parasitic wasps, whereas green aphids are more susceptible to predators such as lady-bird beetles.The final piece of the puzzle was figuring out where the genes came from.
Moran said a long-term association between aphids and pathogenic fungi could make such a gene transfer possible.
The discovery illustrates "the interweaving of organisms and their genomes over time and their merging in different ways," she said. "The distinctness of different genomes and organisms and lineages is much less than we thought."Contact:
Mari N. Jensen | University of Arizona
Complementing conventional antibiotics
24.05.2018 | Goethe-Universität Frankfurt am Main
Building a brain, cell by cell: Researchers make a mini neuron network (of two)
23.05.2018 | Institute of Industrial Science, The University of Tokyo
A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.
The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...
At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.
At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...
There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?
At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...
So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics
Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...
The historic first detection of gravitational waves from colliding black holes far outside our galaxy opened a new window to understanding the universe. A...
02.05.2018 | Event News
13.04.2018 | Event News
12.04.2018 | Event News
24.05.2018 | Ecology, The Environment and Conservation
24.05.2018 | Medical Engineering
24.05.2018 | Physics and Astronomy