Even though domestic plants usually appear radically different from their wild relatives, they are often still able to interbreed. For transgenic crops carrying traits like herbicide resistance, this flexibility could pose a problem if they were to pollinate weedy relatives nearby. In the July issue of GENETICS, Adamczyk-Chauvat et al. examine the extent to which alleles from cultivated oilseed rape introgressed into the genome of wild radish after several generations of cross-pollination. They found that certain regions of the genome were more likely to be passed from domestic to wild plants, suggesting that targeting transgenes into specific genomic locations could limit their putative escape into weeds.

Oilseed rape, also known as rapeseed, is a brilliant yellow flowering plant cultivated around the world for its oil-rich seeds, which are used for animal feed, biodiesel, and edible vegetable oil. Oilseed rape is one of the main transgenic crops worldwide, carrying genes introduced mainly for herbicide resistance. The crop has a very low rate of natural hybridization with wild radish, a weedy relative, but the transfer of herbicide resistance to weeds could pose a major economic problem for farmers.

Wild radish flowers. Photo Brenda Dobbs via Flickr.

The authors grew a population of oilseed rape plants in a natural field environment and pollinated the crops with wild radish. They continued pollinating the hybrid offspring with wild radish for five generations. To trace how the genomes of these two species had merged in the fifth-generation plants, the team chose 307 hybrids with a chromosome number close to the one of wild radish. They identified oilseed rape alleles in each of these hybrids by genotyping a set of markers spanning the genome and found around half the individuals had a detectable oilseed rape allele. However, nearly 70% of markers carried mainly the radish allele—there was a very low probability of introgression (p₁=0.003) at those sites.

In contrast, a few markers were frequently introgressed; interestingly, these markers were not found in random locations but were grouped together in specific regions of the genome. The two most highly introgressed markers were located together on one chromosome and adjacent to several other less frequently introgressed markers. They also found that 30% of introgressed markers were located on the ends of chromosomes rather than in the middle.

These patterns likely arise from the differences in genome structure between oilseed rape and wild radish. Though they can hybridize, they have different chromosome numbers. This striking pattern suggests that using a precisely targeted genome editing method like CRISPR to insert transgenes in select genomic regions could be a possible strategy for keeping them confined to the cultivated species, though more work is needed to see how widely applicable this finding might be.

CITATION:

Gene Introgression in Weeds Depends on Initial Gene Location in the Crop: Brassica napus–Raphanus raphanistrum Model

Katarzyna Adamczyk-Chauvat, Sabrina Delaunay, Anne Vannier, Caroline François, Gwenaëlle Thomas, Frédérique Eber, Maryse Lodé, Marie Gilet, Virginie Huteau, Jérôme Morice, Sylvie Nègre, Cyril Falentin, Olivier Coriton, Henri Darmency, Bachar Alrustom, Eric Jenczewski, Mathieu Rousseau-Gueutin and Anne-Marie Chèvre

GENETICS July 1, 2017 vol. 206 no. 3 1361-1372; https://doi.org/10.1534/genetics.117.201715

http://www.genetics.org/content/206/3/1361

Rotunda, Cannon House Office Building. Photo Credit: Chloe Poston

The House Appropriations Committee completed a review of its fiscal year (FY) 2017 Commerce, Justice, Science, and Related Activities (CJS) spending bill, which provides the budget for the National Science Foundation (NSF). This bill includes language that supports the peer review process carried out by NSF in its funding process. The committee also refrained from any mention of Directorate-level funding at NSF (which would effectively set spending priorities for specific areas of science), instead allowing continued autonomy for the agency to select the scientific proposals it supports. As a push to encourage transparency, the bill directs NSF to ensure that award abstracts are written for a lay audience and include a statement about how the project relates to national interest. This particular provision is not novel; similar language is found in the America COMPETES Act of 2015 and the Scientific Research in the National Interest Act.

Despite the budget request of $7.9 billion from the agency, the House CJS bill sets the budget for NSF at just $7.4 billion (-$57 million). While this reduction would allow for a $46 million increase in research and related activities (which funds investigator-initiated research), it calls for a $113 million funding cut in Major Research Equipment and Facilities Construction. The House CJS bill is a notable departure from the Senate CJS spending bill, which provides $7.5 billion for NSF, but allocates the full funding increase above FY 2016 to design and construct three research class vessels for the Gulf of Mexico and the East and West coasts, leaving no room for a boost in research and related funding.

***LEGISLATIVE ACTION ALERT! Click here to send a letter to your representative urging their support of NSF.

Agencies evaluate shared research resources

Earlier this year, the Division of Biological Infrastructure in the NSF BIO directorate announced that its Collections in Scientific Biological Research (CSBR) would be on a hiatus for the 2016 application cycle. This announcement raised concerns in the GSA community because CSBR funds widely-used model organism stock centers and databases – critical resources that speed research advances and improve research reproducibility. In a May 25th statement, BIO Assistant Director Jim Olds announced that the program would be placed on a biennial award cycle, with proposals accepted in 2017. This shift may have resulted from the outpouring of public criticism and comments underscoring the importance of these shared resources. Meanwhile at the National Institutes of Health (NIH), the National Institute of General Medical Sciences (NIGMS) has released a Request for Information on the need for and support of research resources for the Biomedical Research Community. GSA’s formal response highlighted the importance of shared research resources across the genetics community, and the broad impact of investments in stock centers and databases. Read the full response here.

ACTION ALERT

• To share examples of the benefits of CSBR, potential metrics by which to evaluate CSBR, or other comments, send email to DBICBSR@nsf.gov. While there is no official deadline, comments shared in the near future are more likely to be incorporated in the evaluation process
• To submit comments on shared research resources to NIGMS, send email to nigmsresource@mail.nih.gov by June 3, 2016

GE Crop Study releases final report 

The National Academy of Sciences released its final report on genetically engineered (GE) crops, Genetically Engineered Crops: Experiences and Prospects. The report, a result of  a review of over 900 publications, 80 speakers at public meetings and webinars, and more than 700 comments from members of public, found that GE crops on the market have no adverse effects on human health or biodiversity. The study reported that GE crops have varied economic impact as a result of external socioeconomic factors like the cost of seed and government support for broad dissemination of seeds. The 300+ page report is intended to encourage dialogue between advocates on both sides of the issue. In addition to reviewing existing GE crops, the study also developed a framework to analyze new GE products before they enter the market. Such analyses rely on –omics technology to compare GE products to conventionally bred crops. As for labeling of foods containing GE crops, the committee supported the argument for the sake of transparency, but reiterated that there is no safety concern with GE crops on the market.  “We must move away from sweeping generalizations about GE crops and treat each one as its own entity,” said Fred Gould (North Carolina State University), the study committee Chair. Learn more about the GE crop study here.

Sweeping wage reform impacts postdocs in science

In late May, the Department of Labor released its revisions to the Fair Labor Standards Act. The updated rule requires that postdocs who earn less than $47,476 per year are eligible for overtime when they work more than 40 hours a week. This change, effective December 1, 2016, was embraced by NIH Director Francis Collins in a Huffington Post op-ed coauthored with U.S. Secretary of Labor Thomas Perez. The new baseline salary for postdocs funded directly by NIH will meet the threshold set by the new rule. Catch up on this issue and its implications here.

The Biotechnology Science Coordinating Committee (BSCC), at the behest of the White House Office of Science and Technology Policy (OSTP), held the first of three public meetings to discuss an update to the coordinated framework which serves as the regulatory guidelines for genetically engineered organisms. This meeting provided an opportunity for representatives from the primary agencies involved in GMO regulation, the Food and Drug Administration (FDA), Environmental Protection Agency (EPA), and US Department of Agriculture (USDA) to clarify their roles in the current framework.

Dr. John P. Holdren, Senior Advisor to President Barack Obama and Director of OSTP, opened the meeting, providing the history behind the formation of the coordinated framework and citing rapid advances in the field of gene editing as the impetus to update regulations and speed innovation. The Assistant Director for Biological Innovation at OSTP, Dr. Roberto Barbero delved deeper into the intentions behind the call to update the coordinated framework, highlighting the need to improve transparency in the regulatory process and engage the best scientific evidence as a part of the deliberations. Further, Barbero reiterated the need to support research science that underpins regulatory strategy to maintain evidence-based decision making.

Following OSTP’s introduction, Dr. John Turner, Director of the Biotechnology Risk Analysis Program in the Animal and Plant Health Inspection Service (APHIS) at USDA cited the Plant Protection Act of 2000 as the enabling authority to regulate genetically engineered plants that have a “plant pest component” with the goal of protecting plants and plant products from pests. The animal component of USDA oversight was presented by Dr. Lisa Ferguson, National Director of Policy Permitting and Regulatory Services in APHIS-Veterinary Service. Ferguson demonstrated the USDA authority over genetically engineered animals through the Animal Health Protection Act, specifically refers to the import of animals, the interstate movement of animals infected with certain diseases, and insects which are vectors of animal diseases. To simplify the charge, Ferguson asserted the agency’s goal to regulate anything that might impact the health of US livestock.

“Mais” by Martin CC BY-NC 2.0

The EPA sent two representatives to explain the agency’s role in the coordinated framework to regulation biotechnology. Mike Mendelson, Senior Regulatory Specialist in the Microbial Pesticides Branch of the Office of Pesticides Programs, Biopesticides and Pollution Prevention, began the segment by referencing four key laws that govern the activities his office: Federal Insecticide, Fungicide, and Rodenticide Act; Federal Food, Drug, and Cosmetic Act; Food Quality Protection Act; and the Pesticide Registration Improvement Act. Most relevant to the discussion of genetically engineered organisms are “plant incorporated protectants,” defined as any pesticide substance intended to be produced and used in a living plant and the genetic material necessary for the production of such pesticidal substance. The regulatory reach of EPA also encompasses pesticidal products, such as the Bt Cry1Ab protein and the cry1Ab gene found in Bt corn. Underscoring the need for coordination among federal agencies for pesticides, Mendelson distilled the framework, stating the EPA ensures an organism is safe for use as a pesticide, FDA ensures an organism is safe for use in food and feed, and USDA ensures an organism is safe for agriculture and the environment.

Dr. Mark Segal, Senior Microbiologist in the Office of Pollution Prevention and Toxics at the EPA described the gap-filling function of the Toxic Substances Control Act of 1976. This legislation gave the EPA the authority to regulate the manufacture, use, distribution in commerce, and disposal of chemical substances and mixtures. The oversight includes microorganisms constructed with synthetic genes that are not identical to DNA that would be derived from the same genus as the recipient. Biomass conversion for chemical production, microbial fuel cells, and non-pesticidal agriculture are among the biotechnology products under the purview of the Toxic Substances Control Act. Segal noted that the proposed update to the coordinated framework was timely, as new technologies have byproducts that are excluded from oversight and require “new potential interactions between regulatory agencies that were not anticipated when the framework was published.”

The final presentation was given by Leslie Kux, Associate Commissioner for Policy at the FDA, who referenced the Food and Drug Cosmetic Act‘s provision to ensure the safety of adulterated foods and food additives. Kux noted that transferred genetic material and the intended expression products could be subject to food additives regulations, unless the material and intended products are deemed “generally recognized as safe.” In a 1992 statement, FDA stated “that the regulatory status of a food, irrespective of the method by which it is developed, is dependent upon the objective characteristics of the food.” Stated plainly, the FDA regulates the product of genetic engineering and not the process. In an effort to ensure the safety of genetically engineered foods, the FDA has implemented a pre-market consultation process whereby companies work with the FDA to address all safety and regulatory issues prior to a product coming to market. As a result, over 150 genetically engineered plant varieties that were subject to this consultation process were generally recognized as safe once they were  available to the public, and therefore not regulated by the FDA.

Kux also provided an overview of new animal drug provisions, which prohibit the introduction of unapproved drugs into commerce. This covers all genetically engineered animals bearing heritable rDNA constructs including biopharm animals. Such cases are evaluated by a risk-based approach where applicants must demonstrate that the genetic change is safe to the animal and that food from that animal is safe for human consumption. Genetically engineered animals for research applications are exempt from this regulation to allow for animal drug shipments and labeling, record keeping, and an open path for confidential communication during the development process. To demonstrate successful FDA oversight, Kux highlighted GTC’s Atryn Producing Genetically Engineered Goats, which produce an anti-clotting agent for humans with hereditary clotting disorders in high-risk situations.

Several representatives from various stakeholder organizations were present to provide input to the committee. These ranged from consumer organizations—who asked that the update to the framework mandate all genetically engineered organisms undergo extensive pre- and post-market review—to scientific societies, who requested greater transparency and public engagement to stem public distrust in the biotechnology regulatory process and urged the committee to incorporate the latest scientific evidence into their deliberations.

Dr. Nina Fedoroff

Molecular biologist and long-time GSA member Nina Fedoroff, author of  Mendel in the Kitchen: A Scientist’s View on Genetically Modified Food, also addressed the committee, reminding them of previous scientific studies of genetically modified food which found them to have no negative consequences for human consumption. Her complete remarks are reprinted with her permission here. Those interested in these topics are also encouraged to read Pamela Ronald’s 2011 review on genetically modified crops in GENETICS, which discusses the science behind the testing of genetically engineered food. 

If you feel strongly about the way in which genetically engineered organisms are currently regulated and have suggestions for the committee as they update the framework, you should consider responding to the request for information issued by the Office of Science and Technology Policy. Responses must be received by November 13, 2015, at 5 pm ET and can be submitted through the Federal eRulemaking Portal.

Responses are specifically requested to the following questions:

1. What additional clarification could be provided regarding which biotechnology product areas are within the statutory authority and responsibility of each agency?
2. What additional clarification could be provided regarding the roles that each agency plays for different biotechnology product areas, particularly for those product areas that fall within the responsibility of multiple agencies, and how those roles relate to each other in the course of a regulatory assessment?
3. How can Federal agencies improve their communication to consumers, industry, and other stakeholders regarding the authorities, practices, and bases for decision-making used to ensure the safety of the products of biotechnology?
4. Are there relevant data and information, including case studies, that can inform the update to the CF or the development of the long-term strategy regarding how to improve the transparency, coordination, predictability, and efficiency of the regulatory system for the products of biotechnology?
5. Are there specific issues that should be addressed in the update of the CF or in the long-term strategy in order to increase the transparency, coordination, predictability, and efficiency of the regulatory system for the products of biotechnology?

Related on Genes to Genomes:

• “Biotechnology regulations to be updated,” October 25, 2015
• “Nina Fedoroff comments on GMO regulatory reform,” November 2, 2015.

Also read:

Ronald, P. (2011). Plant genetics, sustainable agriculture and global food security. GENETICS, 188(1), 11-20. doi:10.1534/genetics.111.128553

The comments below were offered by long-time GSA member Nina Fedoroff at a public meeting on updating the Coordinated Framework for the Regulation of Biotechnology held on October 30, 2015. In addition to her academic research career, Dr. Fedoroff served as Science & Technology Adviser to Secretaries of State Condoleeza Rice and Hillary Clinton and U.S. Agency for International Development Administrator Rajiv Shah.

Nina Fedoroff

My name is Dr. Nina Fedoroff. I am a molecular biologist and geneticist, and I was one of the first to apply molecular techniques in plant biology commencing in the 1970s. I have been involved in the regulatory issues around modern genetic modifications (GM) since the early 1980s, when I served on the NIH Recombinant DNA Advisory Committee. I was also one of the authors of the 1987 National Academy of Sciences White Paper titled Introduction of Recombinant DNA-Engineered Organisms into the Environment: Key Issues. Then, as now, there was no evidence that unique hazards attend the use of modern GM techniques or in the movement of genes between unrelated organisms. The paper further states:

The risks associated with the introduction of recombinant DNA-engineered organisms are the same in kind as those associated with the introduction of unmodified organisms and organisms modified by other methods.

And concludes that:

Assessment of the risks of introducing recombinant DNA-engineered organisms into the environment should be based on the nature of the organism and the environment into which it is introduced, not on the method by which it was produced.

The president’s recent directive creates an unprecedented opportunity for the EPA, USDA, and FDA to 1) review the evidence that has accumulated in the intervening 30 years of biosafety research and field experience and 2) to move the regulatory system from de facto process-based to truly risk-based.

Going forward it is critically important to facilitate the use of GM techniques in agriculture. The warming climate, among other factors, is changing pest and disease profiles and distributions. This necessitates far more rapid adaptation responses, particularly for crops, than can be achieved through the older breeding approaches. And because so many different crops and animals are being —and will be—affected, the participation of many more skilled scientists will be necessary to meet these challenges than just those employed by big biotech companies. Tragically, today our public sector agricultural scientists have all but ceased using GM techniques for crop and animal protection and improvement. This is largely because the cost and time involved in obtaining regulatory approval for a GMO release is simply prohibitive.

It is therefore imperative that the present regulatory restructuring yields a framework that is truly risk-based and readily traversed at reasonable cost. The kinds of decision trees that should be developed, albeit based on current knowledge and decades of experience, we already laid out as long ago as the 1989 National Research Council report titled: Field Testing Genetically Modified Organisms: Framework for Decisions. This is especially important in the face of emerging gene modification technologies, such as the CRISPR/Cas system, that provide unprecedented control over what genes are modified and how—something that has never been possible in the entire history of agriculture.

The views expressed in guest posts are those of the author and are not necessarily endorsed by the Genetics Society of America.

The federal regulatory policy in use today for biotechnology products, known as the Coordinated Framework for the Regulation of Biotechnology, was created in 1986 through a joint effort between the U.S. Department of Agriculture (USDA), the Environmental Protection Agency (EPA), the Food and Drug Administration (FDA), the National Institutes of Health (NIH), the National Science Foundation (NSF), and the Occupational Safety and Health Administration (OSHA).  At that time, the overarching group, the Biotechnology Science Coordinating Committee (BSCC) sought to ensure the safety of genetically modified crops, manufactured food, medicine, pesticides, and other uses.

The BSCC’s framework summarized the roles of each agency in this joint regulatory effort as follows:

The FDA regulates products of genetically engineered (GE) organisms that fall within FDA’s authority under the Federal Food, Drug, and Cosmetic (FD&C) Act and other statutes. The FDA is responsible for ensuring the safety of all plant-derived human and animal foods, including those that are from genetically engineered sources. FDA also regulates GE animals under the new animal drug provisions of the FD&C Act, and FDA’s regulations for new animal drugs. (The actual regulated article is the recombinant DNA construct inserted into a specific site in the genome of an animal; as a shorthand, the FDA refers to the regulation of GE animals.)

Within USDA, the Animal and Plant Health Inspection Service (APHIS) is responsible for protecting agriculture from pests and diseases. Under the Plant Protection Act (PPA) and the Animal Health Protection Act (AHPA), USDA-APHIS has regulatory oversight over products of modern biotechnology that could pose a risk to plant and animal health. The AHPA provides authority to prohibit or restrict imports or entry into the United States or dissemination of any pest or disease of livestock. GE animals and insects would be subject to import or transport restrictions if there is a risk to animal health. The PPA, as amended, provides authority to regulate the introduction (i.e., importation, interstate movement, or release into the environment) of certain GE organisms and products. A GE organism is considered a regulated article if the donor organism, recipient organism, vector, or vector agent used in engineering the organism belongs to one of the taxa listed in the regulation and is also considered a plant pest. A GE organism is also regulated when APHIS has reason to believe that the GE organism may be a plant pest. A GE organism is no longer subject to the plant pest provisions of the PPA or to regulatory requirements when APHIS determines that it is unlikely to pose a plant pest risk.

The EPA under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) and the FD&C Act regulates the sale and distribution of all pesticides, including those produced through genetic engineering. This includes microorganisms, biochemicals isolated from organisms, and plant-incorporated protectants (PIPs), a type of pesticide intended to be produced and used in living plants. Under the Toxic Substances Control Act (TSCA), EPA has oversight responsibilities for a wide range of commercial, industrial, and consumer applications of microbial biotechnology. New chemicals produced through those microbial biotechnology applications are subject to premanufacturing review under TSCA.

In July of this year, the Executive Office of the President issued a memorandum directing the primary agencies that regulate the products of biotechnology—EPA, FDA, and USDA—to update the Coordinated Framework, develop a long-term strategy to ensure that the Federal biotechnology regulatory system is prepared for the future products of biotechnology, and commission an expert analysis of the future landscape of biotechnology products to support this effort. This memo comes as gene editing technology advances once again with the advent of the easily adaptable CRISPR, TALEN, and zinc finger nuclease methods.

In response to this memo the White House Office of Science and Technology Policy issued a request for information to “solicit relevant data and information, including case studies, that can assist in the development of the proposed update to the Coordinated Framework for the Regulation of Biotechnology (CF) to clarify the current roles and responsibilities of the EPA, FDA, and USDA” to develop a long-term strategy. Responses must be received by November 13, 2015, at 5 pm ET and can be submitted through the Federal eRulemaking Portal.

Responses are specifically requested to the following questions:

1. What additional clarification could be provided regarding which biotechnology product areas are within the statutory authority and responsibility of each agency?
2. What additional clarification could be provided regarding the roles that each agency plays for different biotechnology product areas, particularly for those product areas that fall within the responsibility of multiple agencies, and how those roles relate to each other in the course of a regulatory assessment?
3. How can Federal agencies improve their communication to consumers, industry, and other stakeholders regarding the authorities, practices, and bases for decision-making used to ensure the safety of the products of biotechnology?
4. Are there relevant data and information, including case studies, that can inform the update to the CF or the development of the long-term strategy regarding how to improve the transparency, coordination, predictability, and efficiency of the regulatory system for the products of biotechnology?
5. Are there specific issues that should be addressed in the update of the CF or in the long-term strategy in order to increase the transparency, coordination, predictability, and efficiency of the regulatory system for the products of biotechnology?

A public meeting where comments from the public are invited will be held on October 30, 2015, at FDA’s White Oak Campus just outside of Washington, DC. The purpose of this meeting is to inform the public of the activities taking place as a result of the July memorandum, invite oral comments from interested parties, and provide information about how to submit written comments, data, or other information to the docket. GSA plans to participate in that meeting, but others who wish to attend are encouraged to register as well.

Additional Information:

• John P. Holdren, Howard Shelanski, Darci Vetter, and Christy Goldfuss. “Improving Transparency and Ensuring Continued Safety in Biotechnology,” White House Blog, July 2, 2015.

If not for a single-nucleotide mutation, each kernel on a juicy corn cob would be trapped inside an inedible casing as tough as a walnut shell. In the July issue of GENETICS, Wang et al. identify an amino acid substitution that was key to the development of the so-called “naked” kernels that characterize modern corn (maize).

The domestication of maize has long fascinated biologists studying evolution. It can provide clues to how organisms change under selection — whether it’s natural selection or selection by humans choosing the most delicious and productive plants to grow in next year’s crop. Maize is a particularly powerful system because many methods and resources are available for its study and because it can be crossed with its wild progenitors for genetic analysis.

Maize was domesticated in Mexico around 9,000 years ago from the grass teosinte. Teosinte seeds are protected by a hard casing that makes them impractical to eat, but ancient plant breeders developed varieties with naked kernels. In these plants, the structures that form the seed case (technically a “fruitcase”) instead become the cob at the center of the ear, leaving the seed exposed for us to eat. Humans effectively turned the teosinte ear inside out, says study leader John Doebley (University of Wisconsin-Madison).

Left: Teosinte ear; right: maize ear; center: ear from the first generation hybrid of a cross between teosinte and maize. Photo credit: John Doebley.

Besides having lost the inconvenient fruitcase, corn kernels today remain firmly attached to the cob, rather than scattering easily as they do in teosinte. The cobs are also much larger, and maize has fewer leaf branches than its ancestor. All these changes evolved relatively quickly, within a few thousand years at most.

Over the last few decades, Doebley and his colleagues have mapped the genes responsible for these differences. They found that genes controlling many of these traits mapped to as few as six genomic locations. Fine-mapping revealed the major gene controlling naked kernel formation is tga1, a transcription factor from a family that regulates floral development.

The teosinte version of tga1 allows formation of an enclosed fruitcase. But maize tga1 disrupts this process, resulting in cases that are smaller and don’t fully enclose the kernel. But what exactly is different about the two versions of the tga1 gene?

To find out, the team compared the tga1 DNA sequence in 16 different maize varieties and 20 varieties of teosinte. They discovered only one variant fixed in all the maize samples but present in none of the teosinte: a single nucleotide change in the coding sequence of tga1 that changes one amino acid in the encoded protein from lysine to asparagine.

When the researchers tested the effect of this substitution on the TGA1 protein, they found that the maize version of the protein had a greater tendency to form dimers. The maize allele also seemed to turn TGA1 into a transcriptional repressor of its target genes, while the teosinte TGA1 did not act as a repressor in reporter assays.

This evidence suggests that repressing TGA target genes alters fruitcase development, contributing to the naked kernel trait.

Consistent with this idea, the researchers found that using RNAi to dampen expression of the maize tga1 gene itself—which should relieve repression of the target genes—enlarged the fruitcase remnant structures in maize. In other words, levels of the maize version of tga1 control the size of the maize structures that would normally form the seed case in teosinte.

These results provide an example of how selection by ancient plant breeders triggered profound structural change in an organism through relatively minor genetic alterations, allowing new traits to evolve rapidly.

“Twenty years ago, it was much harder to study evolution in such detail. It’s exciting that we can now understand complex examples like maize domestication at their most fundamental level,” says Doebley. He also acknowledged the major contributions of lead author Huai Wang for his “series of brilliant experiments that solved a big problem in maize evolution.”

CITATION

Evidence that the origin of naked kernels during maize domestication was caused by a single amino acid substitution in tga1 (2015). Huai Wang, Anthony J. Studer, Qiong Zhao, Robert Meeley, and John F. Doebley. Genetics 200(3): 965-974 doi: 10.1534/genetics.115.175752

http://genetics.org/content/200/3/965