Lindow S.,Microbial Biology |
Newman K.,Microbial Biology |
Chatterjee S.,Microbial Biology |
Baccari C.,Microbial Biology |
And 2 more authors.
Molecular Plant-Microbe Interactions | Year: 2014
The rpfF gene from Xylella fastidiosa, encoding the synthase for diffusible signal factor (DSF), was expressed in 'Freedom' grape to reduce the pathogen's growth and mobility within the plant. Symptoms in such plants were restricted to near the point of inoculation and incidence of disease was two- to fivefold lower than in the parental line. Both the longitudinal and lateral movement of X. fastidiosa in the xylem was also much lower. DSF was detected in both leaves and xylem sap of RpfF-expressing plants using biological sensors, and both 2-Z-tetradecenoic acid, previously identified as a component of X. fastidiosa DSF, and cis-11-methyl-2-dodecenoic acid were detected in xylem sap using electrospray ionization mass spectrometry. A higher proportion of X. fastidiosa cells adhered to xylem vessels of the RpfF-expressing line than parental 'Freedom' plants, reflecting a higher adhesiveness of the pathogen in the presence of DSF. Disease incidence in RpfFexpressing plants in field trials in which plants were either mechanically inoculated with X. fastidiosa or subjected to natural inoculation by sharpshooter vectors was two- to fourfold lower in than that of the parental line. The number of symptomatic leaves on infected shoots was reduced proportionally more than the incidence of infection, reflecting a decreased ability of X. fastidiosa to move within DSFproducing plants. © 2014 The American Phytopathological Society.
News Article | January 28, 2016
The new generation of hybrid plants in the greenhouse. Credit: UZH In today's agriculture, hybrid plants are crucial for the sufficient production of food, feed, fuel and fiber. These crosses between two different varieties are deemed particularly hardy and far more productive than their thoroughbred parent generations. Thanks to hybrid plants, the harvests from types of cereal crop, such as corn, can be more than doubled. However, the positive properties are already lost in the next generation, which is why hybrid seeds need to be reproduced annually. These crosses are costly and time-consuming and farmers are reliant on new seeds every year. Back in the 1930s, two Russian scientists came up with a proposal to simplify this elaborate process: If the first generation of crosses, the so-called F1 hybrid, were able to reproduce asexually, it would retain their increased efficiency. Some plant species naturally reproduce by cloning their seeds, which is referred to as apomixis. The theory that apomixis might preserve the properties of hybrid plants, however, had never been tested in an experimental setup - until now: Professor Ueli Grossniklaus and his team from the Department of Plant and Microbial Biology at the University of Zurich have found proof. "Based on hybrid plants that reproduce apomictically, we demonstrated that the offspring also exhibit the desired biological properties," explains first author Dr. Christian Sailer. "We managed to fix the hybrids' particular efficiency." The plants achieve the same size and yield for at least two more generations. This is in stark contrast to the individual plants of the following generation of conventional F1 hybrids used in agriculture, which differ significantly. Sailer's publication is a key, much-anticipated contribution towards apomixis research and its potential application as it was previously unclear whether the fixation of the genotype would suffice to preserve the advantageous properties of hybrids for generations. For their experiments, the research team created 11 new hybrids using natural apomictic mouse-ear hawkweed (Hieracium pilosella) and reproduced them for two generations through the natural cloning of the seeds. 20 different properties were measured and tested to see if they changed from one plant generation to the next. Moreover, both generations of the same clone were grown in the greenhouse at the same time to expose them to the same environmental conditions and exclude various factors, such as temperature, water and light. More affordable and hardy seeds for small farms "If this special reproduction method could be used in crops, it would slash the cost of producing F1 hybrid seeds," explains Professor Ueli Grossniklaus. "It's not just seed producers who stand to bene-fit, but also subsistence farmers in developing countries." Nowadays, these small farmers usually use less productive native crops for their own personal use. Apomictic reproduction would offer them more affordable access to more productive and hardy hybrid strains. And they would be able to use the seeds from the current harvest for sowing the following year without affecting the yield. According to Grossniklaus, however, its actual use in crops still needs to be tested in detail. More information: Christian Sailer, Bernhard Schmid, Ueli Grossniklaus. Apomixis allows the transgenerational fixation of phenotypes in hybrid plants. Current Biology, 28. Januar 2016. DOI: 10.1016/j.cub.2015.12.045
News Article | December 7, 2016
This perspective was helpful in providing a focus for research in the ensuing decades, which brought about extraordinary discoveries. As a result, many aspects of the form and function of living creatures can now be explained. But already in the 1950s, different observations called into question the seemingly exclusive control of the genes. For example, maize kernels can have different colours even if their DNA sequence is identical. Further investigations brought to light the fact that when individuals with identical genetic material have a different outward appearance, this can be traced back to different degrees of activity on the part of the genes. Whether a particular section of DNA is active or not – i.e., whether it is read – depends to a decisive degree on how densely packed the DNA is. This packing density is influenced by several so-called epigenetic mechanisms. They form a complex machinery that can affix or detach tiny chemical attachments to the DNA. Here, the rule applies that the tighter packed the DNA, the more difficult it is to read – and this means that a particular gene will be more inactive. Living creatures can adjust to a volatile environment by steering their epigenetic mechanisms. In this manner, for example, the epigenetic machinery can ensure that plants can deal better with a hot or arid climate if it at some point they already had to live through a similar situation. So in this sense, the epigenetic markings in the genetic material form a kind of 'stress memory' of the plants. This much is today a matter of consensus among biologists. Several studies, however, suggest that the descendants of stressed plants are also better prepared against the dangers already faced by their ancestors. "However, these studies are a matter of controversial debate," says Ueli Grossniklaus, the director of the Department of Plant and Microbial Biology at the University of Zurich. Like many other epigeneticists who are involved in deciphering these mechanisms, he believes that, "since the evidence is patchy, we can't yet say to what degree acquired characteristics can be transmitted in stable form over several generations." So it still remains to be proven whether epigenetics actually brings organisms long-lasting advantages and thus plays a role in evolution. It's an attractive idea, thinks Grossniklaus, but it's still to be demonstrated. It's not just in plants that results on the heredity of epigenetic markings are causing a stir – the same is true in mice. In order to investigate the possible long-term effects of severe childhood trauma, for example, the research group led by Isabelle Mansuy, a professor of neuro-epigenetics at the University of Zurich and ETH Zurich, has been taking mouse offspring away from their mothers for three hours each day, just a few days after being born. When they reach adulthood, the mice subjected to a difficult infancy displayed behavioural disorders and the corresponding chemical traces in their genetic material. For example, when compared with control mice who were always allowed to remain with their mothers, the traumatised mice spent significantly more time in the brightly lit section of their cage than in the dark section. The behaviour of these mice has allowed the researchers to deduce that the traumatised animals showed symptoms of depression and yet, at the same time, less fear. "They seem to seek danger, such as we often observe in US war veterans who suffer from post-traumatic stress," says Mansuy. Astonishingly, Mansuy's research team has observed the same behavioural abnormalities in the offspring of these traumatised male mice – even where the young mice were never separated from their non-traumatised mothers. Obviously, the sperm contains an epigenetic signal that is also able to codetermine the gene activity of their offspring. This is precisely what causes the greatest unease among many experts. They argue that the genetic material is subjected to epigenetic reprogramming to such a high degree during the maturation of the sperm, and afterwards in the fertilised ovum, that this erases most of the epigenetic markings acquired during the mouse's life. "I agree", says Mansuy, "but it is also proven that some markings survive this reprogramming." There are also other epigenetic mechanisms. In addition to the hereditary material from DNA, sperm also contains a complex collection of small and micro-RNA molecules that can intervene in the epigenetic mechanism, thereby playing an important role in the intergenerational regulation of gene activity. Mansuy believes that her experiments, along with those carried out by others, have served to prove at least in principle the existence of epigenetic inheritance mechanisms. She also reckons that epigenetics may in part explain why there is a familial predisposition to many complex illnesses such as diabetes, cancer and mental illness, even though these inheritance patterns cannot be explained by classical genetics. In comparison with other genetic mutations, epimutations occur roughly a thousand times more often, as Detlef Weigel's group at the Max Planck Institute for Developmental Biology showed in their 2011 investigation of 30 generations of thale cress (Arabidopsis thaliana). Furthermore, epimutations are fundamentally reversible. Perhaps this is why epigenetic traces in our genetic material are transmitted to the next generation, and sometimes also to the generation after that, but then usually disappear again. It is probably just this transitory and uncertain characteristic that nurtures the current disputes – and will probably continue to nurture them until biology has finally understood in full the complex epigenetic machinery of inheritance. Explore further: Not only trauma but also the reversal of trauma is inherited
News Article | November 21, 2016
Five scientists from the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) have been named Fellows of the American Association for the Advancement of Science (AAAS). Election as a AAAS Fellow is an honor bestowed upon AAAS members by their peers. Blakely was recognized for her "distinguished contributions to the field of biophysics, particularly to the biological effects of radiation relevant to cancer therapy and to travel in space." Blakely joined Berkeley Lab in 1975 and worked with John Lawrence, a pioneer of nuclear medicine and brother of Ernest Lawrence, Berkeley Lab's namesake. She did much of her work at the Bevelac, which could accelerate ions as heavy as uranium to high energies. Some of her research involved working out which would be the best beam for cancer therapy. She also studied the effect of radiation on cataracts, which concerns not only cancer patients, but also astronauts, and a field in which she is a leading expert. Last year she was awarded the Berkeley Lab Citation for her extraordinary achievements in science. Gaillard was recognized for her "outstanding contributions to the phenomenology of gauge theories, both in and beyond the standard model, and for inspiring women physicists worldwide." Gaillard became UC Berkeley's first female physics professor in 1981 and joined Berkeley Lab the same year. She published a memoir last year, "A Singularly Unfeminine Profession: One Woman's Journey in Physics," in which she wrote about the slights and frustrations that gradually raised her consciousness as she rose to the top among theoretical physicists trying to understand the complexities of the universe's fundamental particles. She mothered three young children while simultaneously laying the theoretical groundwork for key experiments that proved the validity of the Standard Model, now accepted as the best description of three of the four forces of nature. Matis was recognized for his "leadership roles in advancing physics knowledge through the APS (American Physical Society) and CPEP (Contemporary Physics Education Project), and for his development of a cosmic-ray detector used by schools nationwide." Since 2012, Matis has served as president of the CPEP, an international nonprofit organization of educators and physicists that produces materials to explain physics concepts. A Berkeley Lab physicist since 1983, Matis has also led the Berkeley Lab Cosmic Ray Telescope Project, which provides instructions on how to build a simple, cost-effective particle detector. Matis has worked on particle detectors for experiments at CERN's Large Hadron Collider and at the South Pole, among others. He was honored by the APS with the 2017 Excellence in Physics Education Award. Niyogi was recognized for his "pioneering investigation of the regulation of photosynthesis and mechanisms of photoprotection in plants and algae." Niyogi's research interest lies in understanding how photosynthetic energy conversion works, how it is regulated, and how it might be improved to help meet the world's needs for food and fuel. He is also a Howard Hughes Medical Institute-Gordon and Betty Moore Foundation Investigator and a professor in the Department of Plant and Microbial Biology at UC Berkeley. Earlier this year he was elected to the National Academy of Sciences. David Shuh was recognized for his "distinguished contributions to actinide chemistry, in particular for pioneering spectroscopic characterization of bonding in actinide materials with soft X-ray synchrotron radiation." Shuh, who joined Berkeley Lab in 1992, serves as director for the Glenn T. Seaborg Center, which explores the molecular-scale chemical interactions of heavy elements and also has a mission to educate and train scientists in this field, known as actinide science. Shuh also leads the Heavy Element Chemistry Program and Heavy Element Research Laboratory Program. He is a principal scientist for the Molecular Environmental Sciences Beamline at Berkeley Lab's Advanced Light Source synchrotron and is considered an expert in exploring the electronic structure and chemistry of actinides and rare-earth elements using synchrotron-based experiments and other techniques. This year 391 members have been awarded this honor by AAAS because of their scientifically or socially distinguished efforts to advance science or its applications. New Fellows will be presented their awards on February 18 during the 2017 AAAS Annual Meeting in Boston. The tradition of AAAS Fellows began in 1874. Lawrence Berkeley National Laboratory addresses the world's most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab's scientific expertise has been recognized with 13 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy's Office of Science. For more, visit http://www. . The American Association for the Advancement of Science (AAAS) is the world's largest general scientific society and publisher of the journal Science as well as Science Translational Medicine, Science Signaling, a digital, open-access journal, Science Advances, Science Immunology, and Science Robotics. AAAS was founded in 1848 and includes nearly 250 affiliated societies and academies of science, serving 10 million individuals. Science has the largest paid circulation of any peer-reviewed general science journal in the world. The non-profit AAAS is open to all and fulfills its mission to "advance science and serve society" through initiatives in science policy, international programs, science education, public engagement, and more. For the latest research news, log onto EurekAlert!, the premier science-news Web site, a service of AAAS. See http://www. .
News Article | April 25, 2016
Johanna Roßmanith and her doctoral supervisor Prof. Franz Narberhaus from the Chair of Microbial Biology carried out a successful study where they controlled the type of proteins a bacterium would manufacture and its behavior. This is how they have made a bacterium swim that hadn't previously had the ability to move. The researchers made that possible by combining various modules from the bacterium's RNA in a new way. In the study, which was published in the journal Nucleic Acids Research, the biologists utilized so-called riboswitches, also called RNA switches, and RNA thermometers. Riboswitches detect if there is a surplus of a certain metabolic product in the cell, and they regulate the biosynthesis or intake of that substance, if necessary. RNA thermometers control a number of temperature-sensitive processes. For example, a bacterium that finds its ways from contaminated water into the human body notices the difference in temperature. As a result, it produces certain factors that lead to an infection of the host. "Regulatory RNA modules are attractive for applications in synthetic biology, because they detect signals from the environment directly and instantly switch the subsequent genes on or off," said Roßmanith. An open question was if such components that occur in nature can be combined arbitrarily like Lego bricks in order to develop novel sensors. For her thesis, the PhD student utilised various riboswitches that she coupled in series to a RNA thermometer. Following an alternative strategy, she integrated the thermometer structure in the riboswitch. Both methods resulted in the creation of novel functional elements that respond to a combination of one chemical and one physical signal, in this instance temperature. In order to make the above-mentioned bacteria swim, the researchers placed a gene responsible for bacterial locomotion under the control of the newly combined RNA regulators. The correct signal combination was crucial for the experiment to succeed. The riboswitch required, for example, a certain chemical substance in combination with a certain temperature. "RNA switches are not quite as modular as bricks in a model kit," said Narberhaus. "Ms Roßmanith had to test and optimise many combinations before she achieved functional blocks. Nevertheless, our results show that RNA modules have great potential in biotechnology for controlling processes in bacterial cells in a targeted manner."