REU: The Genetic Basis of Morphological Evolution in Maize

REU：玉米形态进化的遗传基础

• 批准号: 8806889
• 负责人: John Doebley
• 金额: $ 15.6万
• 依托单位: University of Minnesota Saint Paul
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1988
• 资助国家: 美国
• 起止时间: 1988-10-15 至 1992-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8806889&HistoricalAwards=false
• 关键词: REU; Genetic; Basis; Morphological; Evolution

Morphological differentiation in plant species is correlated in general with reproductive isolation and genetic differences. Very different-looking species are usually also reproductively incompatible (hybrids cannot be made, or if obtained, are sterile). Nevertheless, some plant species which are closely related in the genetic sense that they are completely interfertile may look very different morphologically. This situation has compelled plant evolutionists to hypothesize that these exceptional plant species must have undergone rapid morphological evolution. They have changed greatly in appearance in a period of time that was too short to allow them to evolve mechanisms of reproductive isolation. Cultivated maize is one such exceptional species, compared to its wild progenitors, the teosinte corns of Mexico. The genetic basis of such rapid morphological change may depend upon two contrasting modes: changes at a very small number (one to four) of genes with major effects, or numerous changes of many genes, each with small effects. Dr. John Doebley is beginning to test these two hypotheses in his study of genetic effects on morphological changes in the ear of corn, Zea mays subspecies mays. The ear of corn is remarkably different from that of its ancestor, Mexican teosinte, despite the fact that corn and teosinte are completely interfertile and are thought to have diverged only 10,000 years ago under Indian domestication. Tests will be conducted on progeny between corn and teosinte races, analyzing associations between molecular markers on the chromosomes and genes controlling morphological features in corn and teosinte ears. By these means it should be possible to determine the minimum number of genes controlling key morphological differences between corn and teosinte, the chromosomal location of these genes, the mode of action (dominant or recessive), and the percentage of phenotypic variation for which each gene accounts. The data will allow discrimination between two competing theories on the morphological steps involved in the recent origin of the corn ear.

植物物种的形态分化通常与生殖隔离和遗传差异相关。 外观差异很大的物种通常在生殖上也不相容（无法产生杂交种，或者即使获得，也是不育的）。 然而，一些在遗传意义上密切相关、完全不育的植物物种在形态上可能看起来非常不同。 这种情况迫使植物进化论者假设这些特殊的植物物种一定经历了快速的形态进化。 它们在很短的时间内在外观上发生了巨大的变化，以至于它们无法进化出生殖隔离的机制。 与它的野生祖先墨西哥类蜀黍玉米相比，栽培玉米就是这样一种特殊的物种。 这种快速形态变化的遗传基础可能取决于两种截然不同的模式：极少数（一到四个）基因的变化具有重大影响，或许多基因的大量变化，每个基因都具有较小的影响。 约翰·多布利 (John Doebley) 博士开始在他的玉米穗（玉米亚种 mays）形态变化的遗传影响研究中检验这两个假设。 玉米穗与其祖先墨西哥类蜀黍的穗有显着不同，尽管事实上玉米和类蜀黍完全不能生育，并且被认为仅在一万年前在印度驯化过程中出现了分歧。 测试将对玉米和类蜀黍品种之间的后代进行，分析染色体上的分子标记与控制玉米和类蜀黍穗形态特征的基因之间的关联。 通过这些方法，应该可以确定控制玉米和类蜀黍之间关键形态差异的基因的最小数量、这些基因的染色体位置、作用模式（显性或隐性）以及每个基因所占的表型变异的百分比。 这些数据将有助于区分关于玉米穗近期起源的形态步骤的两种相互竞争的理论。