Identification and Characterization of Single Gene Mutations Causing Heterosis in Tomato

PI: Zachary B. Lippman（冷泉港实验室）合作者：Dani Zamir（希伯来大学）在上个世纪，世界主要农作物的农业产量显著增加，从而为不断增长的人口提供了食物。这一切之所以成为可能，主要是因为一个世纪前的发现，即杂交不同的产量较低的自交系玉米品种，可以显著提高杂交或杂交植株的产量。这种杂种优势被称为“杂种优势”，已成为作物育种的基础和激烈研究的焦点。虽然研究已经揭示了控制杂种优势的重要概括，但负责的个体基因和分子网络仍未被确定。这个项目将测试一个新的假设，即单个基因的突变，表面上对植物生长有害，当杂交回正常的非突变植物时，可以产生杂种优势。在“突变杂交”中产生的部分基因活性导致一种新的生长状态，这种状态通过一种称为“剂量”的遗传现象有利于产量。对番茄的初步研究已经发现了可以增加果实产量的多种突变杂交品种。基于这些发现，本项目的目标将是：i)寻找与正常植株杂交时表现出杂种优势的其他番茄突变体，ii)表征生长变化（例如枝数，开花），这些变化是先前确定的两种突变杂交种杂种优势的基础，iii)研究突变杂交种中所有番茄基因活性的新变化。与以往的研究不同，本项目将能够将单个基因的杂种优势效应与特定生长变化和相关基因活性变化联系起来。这一新知识可以用来鉴定导致其他作物品种杂种优势的基因。为了向公众宣传杂种优势和本项目的原理，制定了植物育种和粮食生产的教学计划。具体来说，一个由三部分组成的课程解释了植物形成花朵、果实和种子的过程，该课程是为纽约皇后区一所学生人数不足的小学开发的。来自多种作物的活植物将被用来说明植物从长叶到开花的生长过程中发生的巨大变化。讨论部分将强调环境如何与植物相互作用以刺激花朵和果实的生产，以及植物育种家如何利用这些知识开发新的作物品种。预计这个外展项目将成为未来针对纽约市其他学校的项目的典范。最后，本项目产生的所有数据将通过茄科基因组学网络（http://sgn.cornell.edu/）公开提供。此外，可以从冷泉港实验室（http://www.cshl.edu/public/SCIENCE/lippman.html）和番茄遗传资源中心（http://tgrc.ucdavis.edu/）索取突变杂交品种的种子。

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 (http://www.cshl.edu/public/SCIENCE/lippman.html) and from the Tomato Genetics Resource Center (http://tgrc.ucdavis.edu/).