The research will be published online in this week's Proceedings of the National Academy of Sciences.
"This inverse relationship has been previously reported in animals," said University of Georgia professor and senior author Chung-Jui Tsai. "And in animal genes, when there's a single copy, more often than not you see a higher degree of alternative splicing."
Alternative splicing is the molecular process that allows a single gene to produce many gene products or proteins with potentially different functions. It is an important regulatory mechanism for determining diversity in all plants and animals.
Tsai is W.N. Haynes Professor and Georgia Research Alliance Eminent Scholar, Warnell School of Forestry and Natural Resources, and professor of genetics, Franklin College of Arts and Sciences, at UGA.
Tsai's team set out to investigate the role of a gene that encodes for the enzyme isochorismate synthase (ICS), which has two distinct functions: synthesis of vitamin K for photosynthesis, the conversion of light to energy, and synthesis of salicylic acid, an aspirin-like compound found naturally in most plants that is important for their resistance to diseases. In Arabidopsis, a tiny flowering annual plant that is widely used as a model organism for studying plants, salicylic acid is derived primarily from ICS. The investigators wanted to know the role of the ICS gene in fast-growing and economically important Populus tree species.
The PNAS authors took their cues from Arabidopsis. In this tiny weed, there are two copies of the ICS gene, while there is only one copy of the gene in Populus.
When subjected to stresses, the tiny Arabidopsis plant did what was expected: It produced normal stress-fighting proteins, but from only one of the ICS duplicates. However, the single copy ICS gene in Populus spontaneously produced a mixture of the normal and alternative forms of gene product in equal proportions, and it did not respond to stresses.
Tsai said, "We asked, 'Does the ICS gene behave differently by chance? Or does it reflect something about how disease resistance is controlled in different kinds of plants?'"
Following the discovery of extensive alternative splicing in the Populus ICS gene, the researchers inserted the Populus ICS gene into an Arabidopsis mutant that lacked the stress-fighting ICS copy. The UGA-led research team found that the Populus ICS gene could not be correctly spliced at all in the foreign Arabidopsis host and could not restore the weed's ability to produce salicylic acid.
Tsai explained, "When the correctly spliced Populus ICS gene was inserted, it worked as expected in Arabidopsis. This suggested that some of the signal recognition for splicing is not in the weed any more."
Tsai's research found that in Arabidopsis one of the ICS genes has been recruited for defense. "When these species get attacked, it's important for them to respond quickly and massively using a dedicated ICS gene."
In contrast, Tsai said, woody perennial trees like Populus, which face environmental stress throughout their long lifetimes, have evolved other pathways to synthesize salicylic acid and other chemicals for "constitutive" defense – meaning these compounds are produced all the time – and the primary ICS gene function is photosynthesis.
Tsai concluded, "The gene duplication and alternative splicing of Arabidopsis and Populus reflect their distinct defense strategies."
But the major finding of the research – the relationship between gene copy number, gene sequence and how splicing may have contributed to gene evolution – is what Tsai finds most exciting.
"Sometimes people compare the gene count between the weeds and trees to try to understand what makes a tree a tree. But it's not the gene number that's significant. The tiny weed has approximately 27,000 genes, and Populus has 35,000 to 40,000 genes – it's not that different." Tsai's research shows that it is also how a gene is regulated that contributes to the difference.
Tsai's co-authors on the paper are Yinan Yuan, Michigan Technological University (MTU); Jeng-Der Chung, Taiwan Forestry Research Institute and a former visiting scientist at UGA; Xueyan Fu and Sarah L. Booth, Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University; Priya Ranjan, formerly at MTU and now at Oak Ridge National Laboratory; and UGA scientists Virgil (Ed) Johnson and Scott Harding, also formerly at MTU.
Sam Fahmy | EurekAlert!
Cancer diagnosis: no more needles?
25.05.2018 | Christian-Albrechts-Universität zu Kiel
Less is more? Gene switch for healthy aging found
25.05.2018 | Leibniz-Institut für Alternsforschung - Fritz-Lipmann-Institut e.V. (FLI)
The more electronics steer, accelerate and brake cars, the more important it is to protect them against cyber-attacks. That is why 15 partners from industry and academia will work together over the next three years on new approaches to IT security in self-driving cars. The joint project goes by the name Security For Connected, Autonomous Cars (SecForCARs) and has funding of €7.2 million from the German Federal Ministry of Education and Research. Infineon is leading the project.
Vehicles already offer diverse communication interfaces and more and more automated functions, such as distance and lane-keeping assist systems. At the same...
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...
25.05.2018 | Event News
02.05.2018 | Event News
13.04.2018 | Event News
25.05.2018 | Event News
25.05.2018 | Machine Engineering
25.05.2018 | Life Sciences