(Press-News.org) Powdery mildew is one of the most dreaded plant diseases: The parasitic fungus afflicts crops such as wheat and barley and is responsible for large harvest shortfalls every year. Beat Keller and Thomas Wicker, both plant biologists from the University of Zurich, and their team have been analyzing the genetic material of wheat mildew varieties from Switzerland, England and Israel while the team headed by Paul Schulze-Lefert at the Max Planck Institute for Plant Breeding Research in Cologne studies the genetic material of barley mildew. The results recently published in Nature Genetics and PNAS respectively unveil a long shared history of co-evolution between the host and the pest and the unexpected success of asexually produced mildew offspring. Moreover, the data provides fresh insights into the crop history of wheat and barley and their interaction with the mildew pathogen.
Asexually produced offspring more successful
Like other fungi, mildew reproduces in two ways: Sexually, where the genetic material is recombined, and asexually, where the offspring and the mother fungus are genetically identical. The researchers now demonstrate that the success of the two reproduction methods could not be more different: "Mildew fungi detected on afflicted host plants have only successfully reproduced sexually every few centuries, primarily reproducing asexually instead," explains Wicker.
This baffling fact has more deep-rooted causes: In order to infect the host plant, the mildew fungus needs to be able to successfully disable the plant's defense mechanisms – the parasite has to be perfectly adapted to its host. "In a parasite-host situation, new combinations of genetic material are a disadvantage for the parasite as the adaptation to the host and its defense mechanisms deteriorates as a result." Genetically identical offspring of successful mildew fungi that have already been able to infect the host plant, however, have the ideal genetic prerequisites to be able to attack a host themselves. According to Schulze-Lefert, wheat and barley mildew offspring from asexual reproduction are normally more successful than their sexually reproduced counterparts. Asexual reproduction as a success model seems to be characteristic of many parasitic fungi, including those that afflict humans, such as athlete's foot.
Sex still worthwhile
Based on the gene analyses, the scientists were also able to prove that mildew already lived parasitically on the ancestral form of wheat 10,000 years ago, before wheat were actually domesticated as crops. None of the subsequent genetic changes in the crops due to breeding or spontaneous mutations was ever able to keep the mildew fungus away from wheat in the longer term. And this is precisely where the advantage of sexual reproduction lies and why the usually unsuccessful sexual reproduction cycle is still worthwhile for the mildew fungus: Wheat and mildew are embroiled in a permanent evolutionary arms race. "If wheat improves its defense mechanisms against the parasites, the fungus has to be able to follow suit or it has lost," explains Wicker. "That's only possible by recombining the genetic material; in other words, sexual reproduction."
Evidently, a sexual exchange and mixtures of the genetic material of different mildew varieties have occurred several times in the course of the millennia, giving rise to new mildew varieties that were able to attack new sorts of wheat. The scientists suspect that the grain trade in the ancient world was partly responsible for the emergence of new mildew varieties.
INFORMATION:
Literature:
Thomas Wicker et al. The wheat powdery mildew genome shows the unique evolution of an obligate biotroph. Nature Genetics. July 14, 2013. doi:10.1038/ng.2704
Stéphane Hacquard et al. Mosaic genome structure of the barley powdery mildew pathogen and conservation of transcriptional programs in divergent hosts. PNAS. May 21, 2013. doi/10.1073/pnas130607110
Contact:
Wheat mildew:
Prof. Dr. Beat Keller
Institute of Plant Biology
University of Zurich
Tel. +41 44 634 82 30
E-Mail: bkeller@botinst.uzh.ch
Barley mildew:
Prof. Dr. Paul Schulze-Lefert
Max Planck Institute for Plant Breeding Research
50829 Cologne
Germany
Tel. +49 221 5062 350
E-Mail: schlef@mpiz-koeln.mpg.de
Sexual reproduction only second choice for powdery mildew
2013-07-15
ELSE PRESS RELEASES FROM THIS DATE:
Carnegie Mellon researchers develop artificial cells to study molecular crowding and gene expression
2013-07-15
PITTSBURGH—The interior of a living cell is a crowded place, with proteins and other macromolecules packed tightly together. A team of scientists at Carnegie Mellon University has approximated this molecular crowding in an artificial cellular system and found that tight quarters help the process of gene expression, especially when other conditions are less than ideal.
As the researchers report in an advance online publication by the journal Nature Nanotechnology, these findings may help explain how cells have adapted to the phenomenon of molecular crowding, which has ...
Early spatial reasoning predicts later creativity and innovation, especially in STEM fields
2013-07-15
Exceptional spatial ability at age 13 predicts creative and scholarly achievements over 30 years later, according to results from a new longitudinal study published in Psychological Science, a journal of the Association for Psychological Science.
The study, conducted by psychology researcher David Lubinski and colleagues at Vanderbilt University, provides evidence that early spatial ability — the skill required to mentally manipulate 2D and 3D objects — predicts the development of new knowledge, and especially innovation in science, technology, engineering, and mathematics ...
Undiagnosed pre-diabetes highly prevalent in early Alzheimer's disease study
2013-07-14
BOSTON – When Georgetown University neurologist R. Scott Turner, MD, PhD, began enrolling people with mild to moderate Alzheimer's disease into a nationwide study last year, he expected to find only a handful of participants with undiagnosed glucose intolerance, as all the patients were already under a doctor's care and those with known diabetes were excluded. But Turner says he was "shocked" by how many study participants were found to have pre-diabetes — a finding that is triggering important questions.
Turner's study examines resveratrol, a compound found in red grapes ...
Baseball players enjoy successful long-term results after elbow surgery
2013-07-14
CHICAGO, IL – Baseball players undergoing ulnar collateral ligament (UCL) surgery are able to return to the same or higher level of competition for an extended period of time, according to research presented today at the American Orthopaedic Society for Sports Medicine's (AOSSM) Annual Meeting in Chicago, IL.
"Previous studies showed successful return to play after UCL surgery, but we were also able to evaluate each athlete's career longevity and reason for retirement," commented lead author, Daryl C. Osbahr, MD of MedStar Union Memorial Hospital in Baltimore. "These ...
EARTH: Corn syrup model splits Yellowstone's mantle plume in 2
2013-07-14
Alexandria, VA – One of the greatest controversies in science is what's underneath the Yellowstone supervolcano. The controversy surrounds a unique relationship between a mantle plume (like the one that powers Hawaiian volcanoes) and the subduction zone off the Washington-Oregon coast. Cutting-edge research using a common kitchen ingredient is explored in the latest issue of EARTH Magazine.
Recently published research explores this problem in 3-D, using a model created with corn syrup, fiberglass and a series of hydraulic pistons. What the scientists saw was a plume sliced ...
Getting enough ZZZs may play a part in concussion testing
2013-07-13
CHICAGO, IL – Athletes who didn't get enough sleep the night before undergoing baseline concussion testing didn't perform as well as expected, say researchers presenting their work today at the American Orthopaedic Society for Sports Medicine's (AOSSM) Annual Meeting in Chicago, IL.
"Our results indicate athletes sleeping less than 7 hours the night prior to baseline concussion testing did not do as well on 3 out of 4 ImPACT scores and showed more symptoms," said lead author, Jake McClure, MD from Vanderbilt University. "Because return-to-play decisions often hinge on ...
Type of helmet, may not lower concussion risk
2013-07-13
CHICAGO, IL – 40,000 high school football kids get a concussion every year, but contrary to equipment manufacturers' claims, the specific brand of helmet and helmet age were not associated with lower risk of concussion, say researchers presenting their work today at the American Orthopaedic Society for Sports Medicine's Annual Meeting in Chicago, IL.
"According to our research, lower risks of sustaining a sports-related concussion (SRC) and its severity were not improved based on a specific manufacturer. In addition, the SRC rates were similar for players wearing new ...
Study finds strong pregnancy outcomes for survivors of childhood cancer
2013-07-13
BOSTON -- Although women who survived childhood cancer face an increased risk of infertility, nearly two-thirds of those who tried unsuccessfully to become pregnant for at least a year eventually conceived, according to clinical researchers at Dana-Farber/Boston Children's Cancer and Blood Disorders Center and Brigham and Women's Hospital. This is comparable to the rate of eventual pregnancy among all clinically infertile women.
"Most women think that if they had cancer as a child, then they'll never have children. It turns out that many of them can get pregnant. It ...
Exploring gender dimensions of treatment programs for neglected tropical diseases in Uganda
2013-07-13
TORONTO, ON – Males and females face different challenges in accessing treatment for neglected tropical diseases (NTDs), according to a new study from researchers at the University of Toronto Dalla Lana School of Public Health, Uganda Ministry of Health and Imperial College London. The study, published by PLOS Neglected Tropical Diseases on July 11, explores the role of gender in access to treatment in the Uganda National Neglected Tropical Disease Control Program.
NTDs are a group of parasitic, viral and bacterial diseases that affect at least a billion people worldwide. ...
Geology tracks eruptions, earthquakes, erosion, extinctions & more
2013-07-13
Boulder, Colo., USA – Twenty-five new articles have been posted online ahead of print on Geology's website since 28 June. The science covers a gamut of topics, from microbial mats to super-eruptions; sand to monsoons; glaciers to sinkholes. All Geology articles go through a rigorous peer-review process prior to print. Geology is the highest rated journal for geoscience for the seventh year in a row, according to a 2012 Thomson Reuters survey.
Highlights are provided below. GEOLOGY articles published ahead of print can be accessed online at http://geology.gsapubs.org/content/early/recent. ...