Teosinte branched and the evolution of development

类蜀黍的分支和发展演变

• 批准号: 9513573
• 负责人: John Doebley
• 金额: $ 37.02万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-01-01 至 1999-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9513573&HistoricalAwards=false
• 关键词: Teosinte; branched; evolution; development

Doebley 9513573 teosinte branchedl (tbl ) is a recessive mutant of maize that conditions the plant to have long lateral branches tipped by tassels at the upper nodes and many tillers at the basal nodes. As its name implies, tbl mutant plants show a striking similarity to teosinte, the wild progenitor of maize. Recently, my laboratory determined that tbl was involved in the evolution of maize plant architecture (short lateral branches tipped by ears) from teosinte plant architecture (long lateral branches tipped by tassels). Our model for tbl is that it acts as a repressor of axillary branch development such that the maize allele (Tbl +Maize) engenders strong repression (short branches) and the teosinte allele (tbl +teosinte) weak repression (normally long branches). This model further suggests that tbl +teosinte is environmentally regulated so that the extent of branch elongation in teosinte is a function of the degree of shading from surrounding vegetation. The evolution of maize would have involved a change in tbl expression from environmentally regulated expression to constitutive expression. Recently, my laboratory has molecularly cloned tbl using the Mutator transposable element system. The proposed research will utilize this tbl clone to test the proposed model for tbl and to elucidate the nature of the molecular changes in tbl that were responsible for the evolution of maize from teosinte. First, the molecular structure of tbl including nucleic acid sequence, intron-exon borders, and homology to other known genes will be determined. The sequences of 10 maize and 1() teosinte copies of tbl will also be determined. Phylogenetic and visual comparison of this sample of maize and teosinte alleles will allow the identification of sequence motifs that are found only in maize and not in teosinte. These motifs will be candidates for the molecular event(s) responsible for the functional difference between Tbl +Maize and tbl +teosinte. Second, the pattern of expression of Tbl +Maize and tbl +teosinte will be analyzed to determine if and how the expression of these alleles differs. Under the proposed model, the expression of tbl +teosinte should be influenced by the degree of shading, while Tbl +Maize should be strongly expressed under all environments. Third, the phenotypic effects of the different tbl alleles will be determined. Tests for epistasis between tbl and two other loci thought to be involved in the evolution of plant architecture in maize will be made. The evolution of development has been identified as a focus for developmental biology over the next decade. The proposed research will make significant contributions to the understanding of the evolution of development by assessing how changes in gene structure and expression alter the normal course of plant development leading to the evolution of new adult forms. The proposed research will also make contributions to plant developmental biology and biotechnology. This research will provide for the cloning and structural characterization of an important gene involved in maize development. The cloning and characterization of tbl will provide new tools for the analysis of meristem fate and apical dominance, processes of long-standing interest in plant development. Finally, since increased apical dominance is a common feature of plant domestication including all cereals, many tree species and herbs such as sunflower, the possibility exists that engineering of tbl will enable new advances in crop or tree improvement. 3

Doebley 9513573 teosinte Branch chedl(Tbl)是玉米的一种隐性突变体，它的条件是植株上部有长的侧枝，由雄穗倾倒，在基节有许多分蘖。顾名思义，tbl突变植株与玉米的野生祖先teosinte有着惊人的相似之处。最近，我的实验室确定，tb1参与了玉米植株结构(穗顶端的短侧枝)从teosinte植物结构(长的侧枝由雄穗顶端)进化而来。我们关于tb1的模型是，它作为腋枝发育的抑制因子，使得玉米等位基因(tbl+maize)产生强抑制(短枝)，而teosinte等位基因(tb1+teosinte)产生弱抑制(正常长枝)。这一模型进一步表明，tbl+teosinte是受环境调节的，因此teosinte的枝条伸长程度是周围植被遮荫程度的函数。玉米的进化将涉及到tbl表达从环境调控表达向结构性表达的转变。最近，我的实验室使用突变子转座元件系统分子克隆了tbl。这项拟议的研究将利用这个tbl克隆来测试所提出的tbl模型，并阐明tbl中导致玉米从teosinte进化的分子变化的本质。首先，将确定tb1的分子结构，包括核酸序列、内含子-外显子边界以及与其他已知基因的同源性。Tb1的10个玉米和1()个teosinte拷贝的序列也将被确定。对这一玉米和teosinte等位基因样本进行系统发育和目视比较，将有助于识别仅在玉米中发现而在teosinte中没有的序列基序。这些基序将是导致Tbl+玉米和Tb1+teosinte功能差异的分子事件(S)的候选序列。其次，将分析tbl+玉米和tbl+teosinte的表达模式，以确定这些等位基因的表达是否存在差异以及如何差异。在所提出的模型下，tbl+teosinte的表达应受遮荫程度的影响，而tbl+玉米在所有环境下都应强烈表达。第三，将确定不同tb1等位基因的表型效应。将对tb1和另外两个被认为与玉米植株结构进化有关的基因座之间的上位性进行测试。发育的进化已被确定为未来十年发育生物学的重点。这项研究将通过评估基因结构和表达的变化如何改变植物正常的发育过程而导致新的成体的进化，从而为理解发育的进化做出重要贡献。拟议的研究还将对植物发育生物学和生物技术做出贡献。本研究将为一个与玉米发育有关的重要基因的克隆和结构鉴定提供基础。Tbl的克隆和鉴定将为分析分生组织命运和顶端优势提供新的工具，这两个过程是植物发育中长期感兴趣的过程。最后，由于增加顶端优势是包括所有谷物、许多树种和草本植物(如向日葵)的植物驯化的共同特征，因此存在这样一种可能性，即tbl工程将使作物或树木改良方面取得新的进展。3.