2009-08-012024-05-15https://scholars.lib.ntu.edu.tw/handle/123456789/665137摘要：開花植物能在地球上繁盛的重要適應機制在於花朵形態的多樣化，特別的是那些花朵性狀特化成與傳粉者專一共演化(coevolution)的類群，提供了我們探索花朵形態遺傳發育分化機制，及研究植物種化的機會。在後基因體時代，有許多與開花形態發育有關的目標基因已經被分離出來，然而這些基因卻還沒有被完整的研究出如何控制花朵形態發育，以演化出專一的傳粉性狀的機制。苦苣苔科菫蘭屬的兩個親緣相近的共域種類，因適應不同的專一傳粉者而種化出截然不同的花朵形態。蝴蝶傳粉的Streptocarpus johannis花冠筒發育成號角狀，只留下窄小彎曲的鑰匙孔狀通道讓蝴蝶細長的口器伸入；而蜜蜂傳粉的Streptocarpus rexii則有膨大通直的花冠筒，好讓蜜蜂及蠅類較大的身軀鑽入花中傳粉。這兩種植物由於花瓣迥然相異在野外並不會自然雜交，但在溫室裏可以人工雜交培育出子代。我們計劃利用這兩個傳粉性狀分化種當作親本，利用交配出來的F1子代自交後的F2世代來進行花朵遺傳性狀分離分析(segregation analysis)，以找出花朵中發育介量間的關聯性（例如花冠開口大小、花冠筒長度、雄雌蕊長度對花傳粉性狀形態的影響）。由於在模式植物金魚草中已知CYCLOIDEA、RADIALIS、DIVARICATA、MIXTA及CINCINATA這些基因對花朵的對稱性及花朵形狀扮演了關鍵性角色，它們調控了花朵器官的發育，調節花瓣細胞的分裂與生長，可能進而影響了花朵傳粉性狀分化。我們將分析至少150株F2世代花朵傳粉性狀，將所有個體外表型與基因型做遺傳關聯分析(association analysis)，來釐清這些基因對花朵形態發育的直接效應。另外，遺傳關聯分析也可以幫助我們鑑定出這些基因是否有形成連鎖群(linkage group)現象，且透過基因群組加成調節作用，快速的演化出專一傳粉性狀。在我們實驗先期研究資料中發現，這些影響開花形態基因的確可能有很強的連鎖；我們的目標假說於是認為這些基因也許可以歸類為植物的種化基因，因為若這些基因連鎖後，將可以大幅度提升影響花朵形態變異的程度（per cent of variation explained, PVE）。經由我們的分子遺傳實驗設計，將可以推測出菫蘭屬植物傳粉性狀專一性演化，也許只是藉由幾個主要開花形態基因分化，而得以造成與傳粉者共演化及同域種化現象(sympatric evolution)。從達爾文提出演化論後的一百五十年來，生物學家極力想找出花與傳粉者共演化的遺傳發育機制，這項前瞻性研究將是我們開始瞭解花朵演化發育，甚至開花植物種化原理重要的第一步。<br> Abstract: Flower diversity is the keynote adaptation event for angiosperm to diversify on the earth. The phenomena of coevolution, flowers evolved into a special pollination syndrome to attract certain pollinators, is a particular interest for biologists to explore how specific morphology evolved through the flower developmental control and how speciation works after the evolution of this new flower morphology for certain populations. In post genomic era, several candidate genes relating to flower morphology have been isolated from model plants. Until now, no comprehensive study on what these gene’s function and how these genes’ phenotypic effect on pollination-related flower morphology have been published. Species of the genus Streptocarpus (Cape Primrose, Gesneriaceae) exhibit flowers with pollination syndromes ranging from butterfly flowers with keyhole type corollas to fly flowers with open tube corollas. We crossed fly pollinated flowered S. rexii and the butterfly pollinated flowered S. johannis to generate F1 and F2 offsprings from F1 selfing. By the principle of segregation analysis, we shall be able to trace the inheritance of each flower trait and the contribution of each flower trait to the certain pollination syndrome (e.g. the openness of the corolla tube, the length of the tube, stamen and pistil length). Candidate flower morphology genes from model plant Antirrhinum majus such as CYCLOIDEA (CYC), RADIALIS (RAD), DIVARICATA (DIV), MIXTA and CINCINATA (CIN) have been suggested to function not only in creating zygomorphy but also in altering corolla shape. By genotyping of these genes’ Streptocarpus homologs among more than 150 F2 individuals, we shall find out the associations between genotypes and each flower trait. Genetic association analysis on genotype-phenotype correlation will also enable us testify the putative role of each gene on the flower morphology. Moreover, linkage analysis may help to identify potential linkage groups of these flower genes. Indeed, from our preliminary study, CYC and downstream genes significantly correlated to traits related to the openness of the corolla tubes. This raises the possibility that these flower morphology genes might be classified as “plant speciation genes” because their genetic effects on flower shape are linked. Particularly the linkage groups of gene cluster may account for large proportion of the phenotypic variation（per cent of variation explained, PVE）. Ever since Darwin’s theory of evolution, no evidences have been provided to explain developmental genetic mechanism of plant-pollinator coevolution on flower morphology. Through our experimental design, we shall be able to justify that pollination-related flower morphology in Streptocarpus is probably a result of few major genes’ effect only. This frontier research approach shall be the first important step for us to uncover the evolutionary developmental consequence of flower morphology genes on pollination syndrome, or even the cause of speciation.共演化性狀分離分析遺傳關聯分析連鎖群花朵演化發育種化傳粉性狀Co-evolutionsegregation analysisgenetic association analysislinkage groupspeciationflower symmetrypollination syndrome