A few guys were crazy about apomixis for many years,” says Daniel Grimanelli, a young scientist who is already a grizzled veteran of the field. Settled on a patio outside CIMMYT’s Applied Biotechnology Center, Grimanelli is taking a midmorning break from science. Judging by his three-day stubble, sunglasses, cigarette, and tattered jacket, Grimanelli might just as plausibly have emerged from a serious bender. Thanks to a joint appointment to CIMMYT and the Institut de Recherche pour le Dveloppement in Montpellier, France, the Frenchman was transplanted to Mexico a decade ago, but he speaks English with eloquence and force.
“In the 1970s and early 1980s,” Grimanelli continues, “there were essentially four guys: Yves Savidan in France, Wayne Hanna in Georgia, Victor Sokolov in Russia, and Gian Nogler in Switzerland.” Apomixis, in those days, was a botanical curiosity, nothing more. Hanna recalls encountering it in the form of some odd-looking sorghum plants in a Texas greenhouse; Sokolov, far off in the Siberian city Novosibirsk, devoted his labors to gamma grass, a relative of corn; and Savidan, working at that time in Ivory Coast, was handed a selection of wild West African grasses.
All these plants engage in an odd form of reproduction. Their ovaries produce new embryos on their own, as clones of the mother plant. Yet a few of these plants also engage in sex. So the elder statesmen of apomixis studied the patterns by which this particular genetic trait is inherited when apomictic plants mate with their nonapomictic relatives. “We ended up finding that the trait behaved like a single dominant gene,” says Savidan, who now directs the international partnerships of Agropolis, a publicly funded research consortium in Montpellier. It was an astounding conclusion, and Grimanelli says, it led to an audacious idea: “If it’s that simple, why not put it in crops? Why not crossbreed maize with an apomictic relative? Easy!”
“Easy,” echoes Grimanelli’s colleague Olivier Leblanc dourly.
Grimanelli and Leblanc represent a link between the early generation of such apomixis researchers as Savidan, who used traditional plant breeding, and a new wave of researchers who employ molecular markers, genomic data, and genetic engineering. Savidan moved his apomixis research to
CIMMYT in the late 1980s, and Leblanc and Grimanelli joined him a few years later. It seemed the perfect place. For one thing, CIMMYT’s climate-controlled vault full of seed samples held a treasure-trove of seeds from gamma grass, a bushlike plant that is corn’s closest apomictic relative. More important, CIMMYT’s mission of improving crops for farmers in the developing world squared perfectly with the potential benefits of apomixis.
But a decade of traditional plant breeding yielded only frustration. The researchers tried to crossbreed gamma grass and corn. They produced 300,000 hybrid plants, creations with strange combinations of features of both plants. They tried to backcross those hybrid plants with regular corn, hoping that each generation would bring them closer to an apomictic version of corn. Inevitably, somewhere on the long road toward corn, apomixis disappeared.
Crazy corn: CIMMYT crossed corn with gamma grass, generating a host of odd-looking plants. Gamma grass is in the center (also see top image).
But just as the old approach was dying, a new one was born. In 1999 CIMMYT signed an agreement with a French seed company, Limagrain; a division of Swiss pharmaceutical giant Novartis that has since become Syngenta; and the world’s largest seed company, Pioneer Hi-Bred. The agreement gave the center funding and access to private corn-genome databases. “The new tools have become so powerful,” says Grimanelli. “You can clone genes, modify genes, express genes.” He and Leblanc embarked on a search for apomixis genes, sifting through the sections of DNA that were present in the apomictic form of gamma grass but not in the sexual version. They tracked those genes to a large block of DNA, about one-third of a chromosome, that is always present in the apomictic form of gamma grass. To find the specific genes in this huge field of DNA, the researchers are throwing transposons-small bits of DNA that insert themselves randomly into chromosomes-at that block of DNA. They’re hoping that the transposons will insert themselves into genes that are important for apomixis, disrupting the process. When that occurs, the researchers should be able to locate the transposon and with it, the crucial gene-which they could then insert into corn. But the CIMMYT researchers are not alone in their search for the genetic keys to apomixis. A horde of other researchers, some of them sponsored by small biotech startups, have joined the hunt. Competing projects have sprouted in Germany, Switzerland, Australia, the United Kingdom, France, Mexico, California, Texas, and Utah. Most of the newcomers are not hoping to transfer apomixis genes from one species to another-from gamma grass to corn, for instance. Instead, they’re tinkering with the timing of plants’ own genes to trick them into reproducing without fertilization. The researchers are working out the details of this “synthetic” apomixis through experiments with their favorite “lab rat,” a small mustard plant called Arabidopsis thaliana. The CIMMYT researchers, whose effort also is going to rely heavily on genomics data from better-known plants such as Arabidopsis, say the leap from Arabidopsis to corn is likely to be more difficult than many researchers expect. But still, they say, it will happen. The “incredible dynamism of so many people working on this,” says Grimanelli, will not be denied.