Although epigenetic modifications contribute to trait variability, their effect pales in comparison to standing genetic variation.

The raw material of evolution is genetic variation, but proponents of the “extended evolutionary synthesis” add a new layer to this model: heritable variation in epigenetics. The packaging and tagging of DNA can alter traits without changing the DNA sequence, and in some cases, these changes can be inherited across generations. Can this epigenetic variation play a role in adaptation? Though this question is still under debate, a report published in G3: Genes|Genomes|Genetics suggests that the influence of epigenetic variation on trait variability may be comparatively feeble.

Aller et al. set out to directly compare the influence of genetic and epigenetic variation on an adaptive trait in the flowering plant Arabidopsis thaliana. To do this, they used epigenetic Recombinant Inbred Lines (epiRILs), which are bred from closely related plants with and without a specific mutation in a gene important for maintenance of DNA methylation, such that almost all of the heritable variation in their progeny is attributable to differences in which parts of the genome are methylated— i.e. epigenetic variation. The lines are essentially genetically identical, but each has a different stably-inherited pattern of DNA methylation.

For each epiRIL, the authors measured adaptive traits such as flowering time and accumulation of glucosinolates, which are compounds the plants produce for defence against herbivores and pathogens. The team then compared the variation in this epigenetic system to other studies that investigated the genetic variation underlying those same traits.

Although the authors found significant variation within their epigenetically-driven model, it was much lower than variation in genetically-driven equivalents. This suggests that epigenetic changes are much weaker drivers of variability than the major engine of adaptation: alterations of the genetic code.

CITATION:

Comparison of the Relative Potential for Epigenetic and Genetic Variation To Contribute to Trait Stability

Emma S.T. Aller, Lea M. Jagd, Daniel J. Kliebenstein, Meike Burow

G3: Genes|Genomes|Genetics 2018 8: 1733-1746. DOI: 10.1534/g3.118.200127

http://www.g3journal.org/content/8/5/1733 

There’s no such thing as an obese plant. But that doesn’t mean plants can’t teach us something about fat. In the September issue of GENETICS, Ducos et al. show that a protein that controls fat accumulation in humans has a similar function in Arabidopsis. They also find that the human and plant proteins may be regulated in similar ways, indicating that the pathways controlling fat deposition have deep evolutionary conservation.

In humans, the highly conserved gene WDTC1 has a well-established link with body fat content. It controls the number of fat cells present, and genetic variation in WDTC1 is associated with obesity. The encoded protein acts as a substrate adaptor protein for a ubiquitin ligase complex. It is made up of several characteristic repeat structures, which Ducos et al. noticed were similar to the structure of the Arabidopsis protein ASG2. This gene was known to regulate seed germination in some way, but it was not known whether it was an ortholog of WDTC1.

To confirm the relationship between these plant and animal genes, the researchers first looked for other highly similar proteins in existing sequence databases. A phylogenetic analysis showed WDTC1 and ASG2 cluster together among all the examined sequences from plant and animal, but rarely with fungi groups. ASG2 is also widespread among plants and is found in rice and other diverse species, supporting a very old origin for this gene. The structural similarity of the introns and exons of the plant and animal genes further suggest they arose from a shared common ancestor.

But does the plant version of this gene still function in fat regulation? To test this idea, the researchers knocked out ASG2. Seeds made by these mutant plants were heavier and contained higher levels of monounsaturated fats. They also had denser networks of oil bodies, the structures where fat is stored. These mutant seeds were essentially “obese,” showing that the animal and plant proteins are not only structurally similar, they have similar functions. Some other shared aspects of the structure of these two proteins even suggest that they share the same downstream binding partners, though more work is needed to confirm this possibility.

The remarkable functional conservation of this obesity-linked gene suggests the pathway plays a crucial role in physiology. But fat and oil accumulation are important for more than human health; increased seed fat levels could prove a major boost to crops being bred for biodiesel and food oils.

CITATION

Remarkable Evolutionary Conservation of Antiobesity ADIPOSE/WDTC1 Homologs in Animals and Plants

Eric Ducos, Valentin Vergès, Thomas Dugé de Bernonville, Nathalie Blanc, Nathalie Giglioli-Guivarc’h and Christelle Dutilleul

GENETICS September 1, 2017 vol. 207 no. 1 153-162; https://doi.org/10.1534/genetics.116.198382

http://www.genetics.org/content/207/1/153

Leonid Kruglyak, Professor of Human Genetics and Biological Chemistry and HHMI Investigator at the University of California Los Angeles

Leonid Kruglyak (HHMI/University of California, Los Angeles) has been awarded the 2016 Edward Novitski Prize for his extraordinary level of creativity and intellectual ingenuity in the solution of significant problems in genetics research.

“Dr. Leonid Kruglyak has been a pioneer in human genetics for over 15 years…. he continues to pose questions and do experiments that affect our ability to understand the human genome…and he continues to change the way we think about the genome, how to navigate it, and what those changes mean in transcriptional regulation,” said Elaine A. Ostrander, NIH Distinguished Investigator and Chief of the Cancer Genetics & Comparative Genomics Branch at the National Human Genome Research Institute and one of those nominating Kruglyak for this honor.

Drawing on a combination of mathematical, computational and experimental approaches, Dr. Kruglyak’s innovative contributions have moved the fields of linkage genetics, population genetics, and genomics forward.  His work on statistical standards for genome-wide linkage studies has transformed experimental design and become the gold standard for such experiments. Kruglyak also developed the linkage analysis program GENEHUNTER, which has been responsible for the identification of hundreds of human disease loci. Further, his group pioneered expression quantitative trait locus (eQTL) studies, which enabled variation in global gene expression to be applied to genetics of complex human diseases. In recent years, his laboratory has focused on using genomic technology to establish S. cerevisiae and C. elegans as model organisms for studies of complex genetic variation.

Kruglyak has received the Burroughs Wellcome Fund Innovation Award in Functional Genomics (2000), a MERIT award from the National Institutes of Health (2002), the Agilent Thought Leader Award (2010), and the Curt Stern Award from the American Society of Human Genetics (2015). He is also a fellow of the American Association for the Advancement of Sciences and a long-time member of GSA.

The Novitski Prize recognizes a single experimental accomplishment or a body of work in which an exceptional level of creativity and intellectual ingenuity that has been used to design and execute scientific experiments to solve a difficult problem in genetics. It recognizes the beautiful and intellectually ingenious experimental design and execution involved in genetics scientific discovery. The Prize, established by the Novitski family and GSA, honors the memory of Edward Novitski (1918-2006), a Drosophila geneticist and lifelong GSA member, who specialized in chromosome mechanics and elucidating meiosis through the construction of modified chromosomes.

To learn more about the GSA awards, and to view a list of previous recipients, please see http://www.genetics-gsa.org/awards.

Detlef Weigel,  Director and Professor of Molecular Biology at the Max Plank Institute for Developmental Biology, Tuebingen

Detlef Weigel (Max Plank Institute for Developmental Biology, Tuebingen) has been awarded the GSA Medal for his outstanding contributions to the field of genetics in the last 15 years.

“Detlef’s blend of biology, genetics, and genomics technology has been key to many advances at the intersection of modern plant developmental and evolutionary biology”, said Joanne Chory, Professor and Director of Plant Molecular and Cellular Biology at the Salk institute for Biological Studies, who was one of those nominating Weigel for this honor. “In addition to his tireless service to our community, Detlef is a wonderful colleague whose presence makes everyone’s science excel.”

Using the model plant Arabidopsis thaliana, Dr. Weigel has contributed to three major areas related to flowering: the identification of early events in flower development; dissections of the molecular basis for floral patterns; and the determination of mechanisms for natural flowering time. Notably his group identified florigen, a compound made in leaves that induces flowering. Throughout these investigations, Weigel developed multiple resources for the plant genomics community including activation tagging to create gain of function mutants; leading a consortium that produced AtGenExpress, a gene expression atlas for Arabidopsis; and spearheading with colleagues from the US and Europe the 1001 Genomes project for Arabidopsis thaliana.  The genomic tools his research group has created have facilitated biological breakthroughs in the plant science community and beyond. In his most recent work, Dr. Weigel is integrating genomics approaches with large-scale crossing schemes to study the genes that regulate a suite of adaptive plant traits.

Weigel has received an NSF Young Investigator Award (1994), the Charles Albert Shull Award from the American Society of Plant Biologists (2001), the Otto Bayer Award from the Bayer Foundation (2010), and the Mendel Medal of the Leopoldina (2015). He is a fellow of the American Association of the Advancement of Science and a member of the Heidelberg Academy of Science and Humanities, German National Academy of Sciences Leopoldina, European Molecular Biology Organization, Royal Society of London, and the US National Academy of Sciences.

Jeff Dangl, HHMI-GBMF Plant Science Investigator at the University of North Carolina at Chapel Hill noted that, “his deep rooted understanding of genetics and his technological creativity both drive and serve an exceptionally broad and fearless palette of interesting and important biology.”

The Genetics Society of America Medal is awarded to an individual member of the Society for outstanding contributions to the field of genetics in the last 15 years. Recipients of the GSA Medal are recognized for elegant and highly meaningful contributions to modern genetics within the recent history of the field; awardees exemplify the ingenuity of the GSA membership.

To learn more about the GSA awards, and to view a list of previous recipients, please see http://www.genetics-gsa.org/awards.

GSA members are well represented among the winners of FASEB’s fourth annual BioArt competition: 4 of the 11 winning images were submitting by our members.

The BioArt competition seeks to share the beauty and excitement of biological research with the public by featuring captivating images and illustrations that represent cutting-edge life science research. All winning images and videos are from current or former federally funded investigators and/or members of FASEB societies.

Congratulations to the GSA members!

GSA members Adam Brown and David Biron
University of Chicago, Chicago, IL

Research Focus: Behavioral neurobiology

This image depicts a colony of Caenorhabditis elegans nematode worms feeding on bacteria. The worms congregate in patches where bacteria growth is the densest, in this case forming a ring. C. elegans are one of the simplest organisms with a nervous system, making them a valuable model in neurobiology. Mr. Brown is studying how serotonin, which is also present in the human brain, affects food-seeking and foraging behaviors and which specific nerve cells are involved. His research is supported by a training grant from the NIH National Institute of Mental Health.

Nathanaёl Prunet^1,2, GSA member Elliot Meyerowitz^1,3, and Thomas Jack^2
1California Institute of Technology, Pasadena, CA
²Dartmouth College, Hanover, NH
³Howard Hughes Medical Institute

Research Focus: Stem cells and flower development

Like most flowering plants, the male organs, or stamens, of Arabidopsis flowers surround a central female organ, or pistil. Precise control of which genes are activated in which cells is essential to the development of these adjacent, yet very distinct, structures. In this image of young Arabidopsis flower buds, the gene SUPERMAN (red) is activated at the boundary between the cells fated to form the male and female parts. SUPERMAN activity prevents the central cells, which will ultimately become the female pistil, from activating the masculinizing gene APETALA3 (green). This research seeks to identify principles of stem cell maintenance and cell specialization, which could inform future studies in agriculture, medicine, and other biological fields. The collaborative team of researchers receives support from the NIH National Institute of General Medical Sciences, the National Science Foundation, and the Department of Energy Office of Science.

GSA member Suzana Car, Maria Hindt, Tracy Punshon, and GSA member Mary Lou Guerinot
Dartmouth College, Hanover, NH

Research Focus: Plant biology and nutrition

The essential micronutrient zinc is vital for the function of more than 300 enzymes. Zinc deficiency affects more than two billion people worldwide and can impair the immune system, gastrointestinal function, and brain development. These researchers study how plants acquire, sequester, and distribute zinc with the goal of finding ways to increase the zinc content of crops. Using synchrotron X-ray fluorescence technology, they created this heat map of zinc levels in an Arabidopsis thaliana plant leaf. The National Science Foundation and the NIH National Institute of General Medical Sciences and National Institute of Environmental Health Sciences provide funding for this research program. The Department of Energy Office of Science funds the National Synchrotron Light Source facility, beamline X27A, which was used to create this image.

GSA member Shachi Bhatt and Paul Trainor
Stowers Institute for Medical Research, Kansas City, MO

Research Focus: Developmental biology

Blood vessels and nerve cells run in parallel through the body and are dependent upon each other for proper function. They also follow similar early developmental paths, as seen in this image of an embryonic mouse torso. Drs. Bhatt and Trainor are studying these parallel pathways, focusing on a molecule implicated in controlling genes during the early development of blood vessels (gray) and nerve cells (red). Detailed knowledge of normal developmental processes forms a critical foundation for research on birth defects and other diseases affecting the development of these organ systems.

Additional Information:

• “BioArt Image and Video Competition 2015 Winners Announced,” November 24, 2015.