"Preventing weeds from growing is a difficult and very expensive task; it is a major problem in modern agriculture."
By JUDY SIEGEL-ITZKOVICHplants 88(photo credit: )
Herbicide-resistant plants have been engineered by scientists at the Technion-Israel Institute of Technology, in collaboration with a Hebrew University team. The results are published recently in Nature Biotechnology. One might wonder why they bothered, as herbicides are needed to destroy weeds that crowd out edible crops.
But the team explain the method to their madness: "Introduction of a herbicide-resistance trait in commercial plants is highly desirable because it allows novel herbicide management options, eliminating weeds, particularly those that are closely related to the crop. The traditional methods of generating herbicide-tolerant crops are based on either breeding under selective pressure or crossing a specific crop with species that exhibit herbicide resistance. More recently, cell culture selection has also been used to obtain herbicide-resistant crops. We've targeted the family of carbamate herbicides, which have been generally used as germination inhibitors. We designed and synthesized a carbamate herbicide that can be efficiently destroyed by a specific antibody. Every antibody molecule is a protein that is encoded by a specific gene, and that gene can be cloned into a given organism. Our work suggests that in vivo expression of catalytic antibodies could become a general strategy for phenotype modification, not only in plants but also in other organisms."
Thus the scientists designed both a new herbicide and a catalytic antibody that destroys it. Then they cloned the gene of that antibody in Arabidopsis thaliana plants, demonstrating that the resultant transgenic plants were completely resistant to the herbicide.
"Preventing weeds from growing is a difficult and very expensive task; it is a major problem in modern agriculture because weeds can be harmful not only to domesticated plants but also to livestock," explains Prof. Ehud Keinan of the Technion's chemistry department, who carried out this research together with two Technion graduate students, Avidor Shulman and Ira Ben Shir, as well as Prof. Shmuel Wolf and graduate student Yael Weiss of HU's faculty of agricultural, food and environmental quality sciences in Rehovot.
Keinan, editor of the 2005 book Catalytic Antibodies, explains: "The science of catalytic antibodies is primarily a chemical enterprise which mergers the remarkable diversity of the immune system with a programmable design by the experimenter. Over the past two decades, this creative area of research at the interface between chemistry and immunology has produced catalytic monoclonal antibodies for more than 100 different reactions. The growing list of useful applications includes selective organic synthesis, biosensing, mechanistic insights of biocatalysis, insights into evolution of biocatalysis, and medicinal applications, including cancer chemotherapy. Our successful engineering of herbicide-resistant plants highlights a relatively unexplored opportunity - the in vivo modification of an organism phenotype by incorporating the gene that encodes for a catalytic antibody into the genome of that organism. The key message is that an appropriately designed catalytic antibody could solve any problem that is defined in the form of a chemical reaction.
"This line of research offers attractive opportunities in biotechnology, chemical industry, agriculture and medicine."
ROAD ETIQUETTE PAYS
A new University of Michigan study - not really relevant to Israel because of the insane behavior its drivers - has concluded that if all drivers were polite, they would get where they're going faster. The researchers found that traffic metering systems that incorporate new algorithms for merging could reduce the seriousness of traffic slowdowns that originate near freeway on-ramps.
Prof. Craig Davis, a retired Ford executive now at the university, studied highway merging to see how current on-ramp traffic meter systems could be made more effective. Currently, meter systems try to improve traffic flow by letting a certain number of cars enter the highway each minute, based on how many cars are already there. Traffic metering has been around for a long time, and many large US cities have metering systems. Davis says there are two basic types of traffic congestion: gridlock-type jams where cars stop, and the synchronous flow-type congestion, where two or more lanes of traffic all slow down to the same speed. Synchronous flow happens often near on-ramps, when cars don't give one another enough room to merge, or when too many cars are on the road.
Metering systems use computer algorithms to try to predict when a jam may occur, typically based on occupancy. Davis, however, based his algorithm on the throughput, and on the rate at which vehicles are merging, not on highway occupancy. He found that traffic jams happen when throughput exceeds about 1,900 cars per hour per lane; after that, capacity drops by 10% or more.
Davis says that in the absence of metering systems, simple politeness would go a long way toward thinning sludgy traffic near on-ramps. But letting people merge is helpful only if you don't slow down too much to do so.
"If you can do it without slowing down very much, that allows the driver who's entering to enter at a higher speed," Davis said. "If they have to crawl along waiting for an opening, they slow down the other vehicles on the freeway."
If you can safely move over a lane and allow a vehicle to merge, that is even better, he adds.
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