Sequence-specific nucleases have been applied to engineer targeted modifications in polyploid genomes1, but simultaneous modification of multiple homoeoalleles has not been reported. Here we use transcription activator–like effector nuclease (TALEN)2,3 and clustered, regularly interspaced, short palindromic repeats (CRISPR)-Cas9 (refs. 4,5) technologies in hexaploid bread wheat to introduce targeted mutations in the three homoeoalleles that encode MILDEW- RESISTANCE LOCUS (MLO) proteins6. Genetic redundancy has prevented evaluation of whether mutation of all three MLO alleles in bread wheat might confer resistance to powdery mildew, a trait not found in natural populations7. We show that TALEN-induced mutation of all three TaMLO homoeologs in the same plant confers heritable broad-spectrum resistanceto powdery mildew. We further use CRISPR-Cas9 technologyto generate transgenic wheat plants that carry mutations inthe TaMLO-A1 allele. We also demonstrate the feasibility of engineering targeted DNA insertion in bread wheat through nonhomologous end joining of the double-strand breaks caused by TALENs. Our findings provide a methodological framework to improve polyploid crops.
Achieving sustainable global food security is one of humanity’s contemporary challenges. Here we present an analysis identifying key “global leverage points” that offer the best opportunities to improve both global food security and environmental sustainability. We find that a relatively small set of places and actions could provide enough new calories to meet the basic needs for more than 3 billion people, address many environmental impacts with global consequences, and focus food waste reduction on the commodities with the greatest impact on food security. These leverage points in the global food system can help guide how nongovernmental organizations, foundations, governments, citizens’ groups, and businesses prioritize actions.
New data released Monday shows humanity has just unlocked another achievement in the race to cook the planet: The last three months were collectively the warmest ever experienced since record-keeping began in the late 1800s. The Japan Meteorological Agency said June 2014 was the warmest June globally since at least...
Sexual differentiation in eukaryotes is manifested in two fundamentally different ways. Unicellular species may have mating types where gametes are morphologically identical but can only mate with those expressing a different mating type than their own, while multicellular species such as plants and animals have male and female sexes or separate reproductive structures that produce sperm and eggs. The relationship between mating types and sexes and whether or how an ancestral mating-type system could have evolved into a sexually dimorphic system are unknown. In this study we investigated sex determination in the multicellular green alga Volvox carteri, a species with genetic sex determination; we established the relationship of V. carteri sexes to the mating types of its unicellular relative,Chlamydomonas reinhardtii. Theoretical work has suggested that sexual dimorphism could be acquired by linkage of gamete size-regulatory genes to an ancestral mating-type locus. Instead, we found that a single ancestral mating locus gene, MID, evolved from its role in determining mating type in C. reinhardtii to determine either spermatogenesis or oogenesis inV. carteri. Our findings establish genetic and evolutionary continuity between the mating-type specification and sex determination pathways of unicellular and multicellular volvocine algae, and will enable a greater understanding of how a transcriptional regulator, MID, acquired control over a complex developmental pathway.
While not the first to use additive manufacturing to create buildings, a Chinese company is using 3D printing technology to build cheap housing out of recycled material at a rate of up to 10 structures in 24 hours.
Ian Sanders wants to feed the world. A soft-spoken Brit, Sanders studies fungus genetics in a lab at the University of Lausanne in Switzerland. But fear not, he’s not on a mad-scientist quest to get the world to eat protein pastes made from ground-up fungi. Still, he believes—he’s sure—that these microbes will be critical to meeting the world’s future food needs.
Sanders’s eyes widen with delight and almost childlike glee when he talks about a microscopic life form called mycorrhizal fungus, his chosen lifetime research subject. Mycorrhizal fungi live in a tightly wound, mutually beneficial embrace with most plants on the planet. Years of dedication have made Sanders into one of the world’s foremost experts on the genetics of the microbe, and he recently was part of a team that sequenced the first mycorrhizal fungi genome.
Despite his drive, Sanders comes across as light-hearted as he teases and jokes with fellow researchers. But he loses his affable smile as he fires off facts about the upcoming food shortage: The world’s population is expected to increase to between 9 billion and 16 billion people. Five million people per year die of direct causes of malnutrition. Three and a half million of those are children under five. Today, we have the means to grow enough food to feed all those people, but we will most certainly need to produce more in the very near future.
Sanders may have come up with a way to do just that. He has successfully bred custom varieties of microbes that can help plants produce more food. It’s one of the ultimate goals of farming research—more food with, he hopes, little or no environmental downside.
Scientists say an outbreak of beet western yellows virus is one of the worst cases ever seen in Australia.
Early estimates suggest up to 10,000 hectares of canola have been affected, in South Australia's lower north, mid north and lower mallee regions. The virus is transported by green peach aphids, which have thrived in the state's recent warm and humid weather. Ag consultant Mick Faulkner says agronomists felt like they'd been "blind-sided" after not being able to work out what had been affecting crops. "It took everyone a fair bit of time to realise that we weren't killing the aphids," Mr Faulkner said. "Green paddocks are now brown. "Those that have been affected, I have grave fears that they won't yield anything at all."
Virus halted for now - The South Australian Research and Development Institute (SARDI) says it's now testing samples to confirm how the virus is spreading and where else it might turn up. Pulse pathologist Jenny Davidson says with cooler weather, the virus-transmitting aphids aren't moving and at the moment the best thing growers can do is "nothing", "We expect that the spread of this virus would've stopped for now, so there's no point people going out and spraying aphids now," she says. "It's also important growers ascertain it actually is the virus causing problems in their canola crops, there may be other things going on as well. "The potential risk is what these aphids will do in spring time. "We're not sure whether or not pulse crops are at risk but we'll have that information back well and truly before the spring time flights." Ms Davidson says the virus isn't uncommon, but what is unusual is the extent of damage and infection being seen. She says it's taken everyone by surprise. "I've never seen this level of damage from any virus in crops," Ms Davidson says. "It's the magnitude of what we're dealing with that is totally un-expected."
Author Summary Plants and their pathogens are engaged in an endless evolutionary battle. The invention of new strategies by pathogens pushes plants to continuously update their defenses. This in turn leads the pathogens to circumvent these new defenses, and so on. Given the abundance of potential enemies, it is therefore not surprising that genes involved in defense against pathogens are among the most variable in plants. A drawback of this extreme variation in pathogen-recognition mechanisms is that at times the plant mistakes itself for an enemy, leading to autonomous activation of defense responses in the absence of pathogens. Conventional models for this phenomenon, called hybrid necrosis, require the interaction between two different genes. Here we show instead that hybrid necrosis can be triggered by interactions between variants of a single gene, ACD6 (ACCELERATED CELL DEATH 6). Several of these variants are common in natural Arabidopsis thaliana populations and can interact to give different levels of activation of the immune system. Our results provide important information into the evolution and operation of the plant defense system. Moreover, the abundant presence of ACD6 functional variation suggests a major role for this gene in modulating plant defenses in nature.
For decades, scientists have tried to understand the complex and gruesome relationship between the parasitic emerald wasp Ampulex compressa and its much larger victim, the common household cockroach Periplaneta americana.
Landrace rice in Thailand consists of managed populations grown under traditional and long-standing agricultural practices. These populations evolve both in response to environmental conditions within the local agro-ecosystem and in response to human activities. Single landraces are grown across varying environments and recently have experienced temporal changes in local environments due to climate change. Here we assess the interplay between natural selection in a changing climate and human-mediated selection on the population genetic structure of Muey Nawng, a local landrace of Thai rice. Genetic diversity and population structure of landrace rice were assessed by a STRUCTURE analysis of 20 microsatellite loci. The first exon–intron junction of the waxy gene was sequenced to determine genotypes for glutinous or non-glutinous grain starch. Muey Nawng rice is genetically variable and is structured based on starch grain types and the level of resistance to gall midge pest. A strong positive correlation was found between genetic diversity and the percentage of gall midge infestation. Variation in the waxy locus is correlated with starch quality; selection for non-glutinous rice appears to involve additional genes. The dynamics of genetic diversity within Muey Nawng rice depends on three factors: (a) a genetic bottleneck caused by strong selection associated with gall midge infestation, (b) selection by local farmers for starch quality and (c) variation introduced by farmer practices for cultivation and seed exchange. These results, when taken in total, document the ability of landrace rice to quickly evolve in response to both natural and human-mediated selection.
Developing high yielding varieties with broad-spectrum and durable disease resistance is the ultimate goal of crop breeding. In plants, immune receptors of the NB-LRR class mediate race-specific resistance against pathogen attack. This type of resistance is often rapidly overcome by newly adapted pathogen races when employed in agriculture. The stacking of different resistance genes or alleles in F1 hybrids or in pyramided lines is a promising strategy to achieve more durable resistance. Here, we identify a molecular mechanism which can negatively interfere with the allele-pyramiding approach. We show that pairwise combinations of different alleles of the powdery-mildew-resistance gene Pm3 in F1 hybrids and stacked transgenic wheat lines can result in suppression of Pm3-based resistance. This effect is independent of the genetic background and solely dependent on the Pm3 alleles. Suppression occurs at the post-translational level as neither RNA nor protein levels of the suppressed alleles are affected. Using a transient-expression system in Nicotiana benthamiana, the LRR domain was identified as the suppression-conferring domain. The results of this study suggest that the expression of closely related NB-LRR resistance genes or alleles in the same genotype can lead to dominant-negative interactions. These findings provide a molecular explanation for the frequently observed ineffectiveness of resistance genes introduced from the secondary gene pool into polyploid crop species and mark an important step to overcome this limitation.