PI: Zachary B. Lippman (Cold Spring Harbor Laboratory) Collaborator: Dani Zamir (Hebrew University)
The agricultural yields of the world's major crop plants have increased significantly in the last century, thus providing food for an ever-growing population. This was made possible primarily through the century-old discovery that crossing different poor-yielding inbred varieties of corn causes a remarkable increase in yield among the inter-crossed, or hybrid, plants. Such hybrid vigor, termed "heterosis", has since become a foundation for crop breeding and a focus of intense research. While studies have revealed important generalizations about what controls heterosis, the individual genes and molecular networks responsible have still not been identified. This project will test a new hypothesis, namely that a mutation in a single gene, which is seemingly detrimental to plant growth, can cause heterosis when hybridized back to a normal non-mutant plant. The resulting partial gene activity in the "mutant hybrid" results in a new state of growth that is beneficial to yield through a genetic phenomenon called "dosage". Preliminary research in tomato has already identified multiple mutant hybrids that increase fruit production. Based on these findings, the goals of this project will be to: i) search for additional tomato mutants that show heterosis when hybridized with normal plants, ii) characterize the changes in growth (e.g. branch number, flower production) that are the basis for heterosis in two previously identified mutant hybrids, and iii) study novel changes in the activity of all tomato genes in mutant hybrids. Unlike previous studies, this project will be able to link heterotic effects of a single gene with specific changes in growth and relevant changes in gene activity. This new knowledge can then be harnessed to identify genes causing heterosis in other crop species.
To promote educational outreach about heterosis and the principles of this project to the general public, a teaching program about plant breeding and food production has been developed. Specifically, a three-part lesson explaining the processes by which plants make flowers, fruits, and seeds has been developed for an elementary school with an underrepresented student population in Queens, New York. Live plants from multiple crops will be used to illustrate the dramatic changes in growth that occur as plants switch from making leaves to making flowers. Discussion sections will emphasize how the environment interacts with plants to stimulate flower and fruit production, and how plant breeders leverage this knowledge to develop new crop varieties. It is anticipated that this outreach project will serve as a model for future programs that will target additional schools in New York City. Finally, all data generated in this project will be made publicly available through the Solanaceae Genomics Network (http://sgn.cornell.edu/). In addition, seeds from mutant hybrids can be requested from Cold Spring Harbor Laboratory (www.cshl.edu/public/SCIENCE/lippman.html) and from the Tomato Genetics Resource Center (http://tgrc.ucdavis.edu/).
