For the Love of Wheat

Three Israelis from different generations and backgrounds – one a former kibbutznik, the other from France and the third from an Arab village – all wanted to be agronomists yet fell in the love with the science of wheat.

 

As a member of Kibbutz Mishmar David in the 1950s, Prof. Moshe Feldman spent his days helping to plant and harvest the kibbutz’s 4,000 dunams of crops. From his early childhood he had loved nature: “Becoming an agronomist was the natural choice,” he says. But after a year’s study in Jerusalem, he was drawn to biology, particularly its evolutionary aspects. After completing his postdoctoral studies, in the course of which he had the opportunity to work with world-renowned wheat scientist Ernest R. Sears, he came to the Weizmann Institute in 1969 to continue probing the secret to wheat’s enormous success as an adapter: It has flourished all over the world, whether in the Brazilian tropics, the semi-arid areas of Sudan or underneath Canadian snow. “Wheat laid the foundation for civilization as we know it,” says Feldman. “Having learned to cultivate wheat, humans were able to settle in one place for long periods of time, building villages and towns. The wild wheat species that humans first cultivated – ‘the mother of all wheat’ – was discovered in Israel and still grows in these parts.”

 

About a decade later, along came a student, now Prof. Avi Levy, who shared Feldman’s fascination with wheat. He had made aliyah from France at the age of 17 and sought to realize the Zionist dream to its fullest – to work in agriculture in the land of Israel. “My mother cried when she heard I wasn’t going to be a doctor,” he says. He, too, began studying agriculture but became absorbed in wheat genetics. “Wheat is a small, beautiful, modest plant, with very few needs,” says Levy, “and yet its genetics is extremely complex.” He began his doctoral studies at Weizmann under Feldman, whose research in wheat genetics and evolution was by then well known. After completing his postdoctoral work in Stanford, he returned to the Institute as an independent researcher, inspired by Feldman to continue in this field. “But I had to prove that I wasn’t just continuing Mossik’s [Moshe’s nickname] ideas,” he says jokingly. So he branched off to a new topic, the dynamics of genes in other species. “Fortunately, my research proved in time to be central to wheat studies,” he says, and the door reopened to his favorite organism.

 

About four years ago, another wheat enthusiast joined their ranks – graduate student Khalil Kashkush. “When I was born, the first things I saw were strawberries, flowers and wheat,” he says, referring to the produce on his father’s farm in the Arab village of Qalansuwa. The crops’ dependence on rain had made him dream as a young child that one day he would devise a strain of wheat that needed no water. He decided to become an agronomist. “Like Avi’s mother, mine also wanted me to be a doctor. Now she consoles herself that at least I’ll have the title ‘Dr.’,” he laughs. His studies continually leave him feeling that he doesn’t know enough – and so, agronomist dream deferred, he is now completing his doctoral degree in the plant sciences. His work with advisors Feldman and Levy has already led to the publication of three articles in major scientific journals. “Khalil has a lot of spirit and the courage to do things that others before him haven’t done,” says Feldman. “We have high hopes for him. He is going to a leading laboratory to do his postdoctoral work and if he proves himself there, he’ll have an open ticket to all research centers.” Levy adds: “The future will tell, but Moshe, an inspiring teacher, might have laid the foundation for a dynasty of wheat geneticists at the Weizmann Institute of Science.”

 

Wheat might hold clues to one of the most mystifying questions in human evolution: Did a primitive creature double its genome around 500 million years ago, creating the genomic leap that led to the creation of all mammals?  

 

Wheat has doubled its genome several times in the past, creating new species of wheat virtually overnight. “Genomic doubling can be easily induced in the lab when it comes to wheat,” says Levy, “which is why it might provide insight into one of the events that might have shaped the human genome.”

 

Though for many years considered an exotic feature of plants, genome doubling is today recognized as a widespread force that has influenced the evolution of the animal, plant and fungi kingdoms. But human evolution? Scientists have found that many duplicated segments in the human genome date back to approximately 500 million years ago, suggesting that a whole genome duplication event may have occurred at that time. Yet this sort of “genetic archaeology” has its obstacles: Genes change over time and what could have begun as the perfect duplication of a gene might have altered over millions of years. Studying wheat could help scientists visualize what our genome would look like today if such a doubling event had indeed taken place in our past.

 

The team has uncovered several events that occur after genomic doubling. One finding was recently published in Nature Genetics. Doubling of genetic information was known to cause “genomic shock.” Genes that are normally dormant wake up and start interfering with the normal function of other genes. These genes are called “jumping genes” because they move around the DNA, “stepping on” other genes. What wasn’t known was that jumping genes have much subtler ways of sowing confusion: “Even when they don’t jump, they can turn neighboring genes on and off, reversing their activity,” says Levy. Since the publication of their article they have received reactions from many scientists who believe that the same kind of phenomenon occurs in human cells, which also contain many jumping genes.

 

The genome of wheat as we know it today is actually an amalgam of several wheat species, whose genomes can serve as genetic backup systems. The extra gene copies in the “backup genomes” come into play if some genes become mutated.  

 

If one of the primitive creatures serving as our distant forefathers doubled its genome, the extra gene copies, or “backup systems,” might have been used as playdough for creating new functions. Feldman: “The sudden increase in genetic information together with tolerance to mutations might have led to the creation of new genes, increased genetic complexity and, gradually, to the development of more sophisticated species.”