臺灣博碩士論文加值系統

The great diversity of floral shape arouses the natural curiosity to explore the underlying genetic control. Floral zygomorphy as a key innovation to promote plant-pollinator specialization has been proposed to facilitate floral shape diversification. CYCLOIDEA (CYC), RADIALIS (RAD), and DIVARICATA (DIV) have been identified to establish floral zygomorphy. With the ability of regulating cell division and cell growth differentially along the dorsoventral axis, these zygomorphy genes are proposed to be involved in the establishment of different pollination syndromes. In addition, MIXTA-LIKE (MYBML) genes, which are identified to act on the floral architecture via controlling cell shape, are also proposed to be involved in this process. However, no genetic analysis on the phenotypic effects of these genes on floral shape variation related to different pollination syndromes has ever been carried out. Species of the genus Streptocarpus (Cape Primrose, Gesneriaceae) exhibit flowers with pollination syndromes ranging from butterfly flowers with keyhole type corollas, fly flowers with open tube corollas to bird flowers with narrow tubular red corollas. The open tube flowered S. rexii and the keyhole flowered S. johannis were crossed to produced F1 and 119 F2 plants. Association analysis among 119 F2 individuals revealed that StrRAD1 had phenotypic effects on the overall corolla tube length and total stamen length, whereas StrDIV2 affected the diameter of the undilated part of the corolla tube(, an important trait likely correlated with the proboscis length of potential pollinators). In addition, StrCYC1A and StrMYBML2 formed a strong linkage group, and significantly influenced the diameter of the tube opening and the dilated part of the corolla tube, the key characters that define the size of the ‘insect visiting chamber’, and hence effective pollinator. Both traits are critical for the establishment of different pollination syndromes in Streptocarpus. This finding, the first reported genetic link between zygomorphy genes and the differentiation of pollination syndromes, implied that the zygomorphy genes not only act on the establishment of zygomorphy but also on the evolution of floral diversification.

謝辭 I
摘要 II
Abstract III
Table of Contents V
List of Figures VIII
List of Tables X
1. Introduction 1
1.1. Floral diversity and pollination syndromes 1
1.2. The genetic basis of pollination syndromes 3
1.3. What are the candidate genes? 8
1.3.1. Floral zygomorphy and floral shape diversity 8
1.3.2. The molecular developmental genetics of zygomorphy 9
1.3.2.1. CYCLOIDEA and DICHOTOMA 11
1.3.2.2. DIVARICATA 16
1.3.2.3. RADIALIS 19
1.3.3. Floral zygomorphy in Gesneriaceae 20
1.3.4. Other Candidate genes 21
1.3.4.1. MIXTA-LIKE genes 21
1.4. Streptocarpus 24
1.5. Aim of this study 27
2. Materials and Methods 28
2.1. Plant materials 28
2.2. Morphological study 29
2.2.1. Floral traits measurement 29
2.3. Molecular techniques 31
2.3.1. Nucleic acid extraction 31
2.3.1.1. DNA extraction 31
2.3.1.2. RNA extraction 32
2.3.2. First strand cDNA synthesis 33
2.3.3. Polymerase chain reaction 34
2.3.3.1. Standard PCR 34
2.3.3.2. Thermal Asymmetric InterLaced PCR (TAIL-PCR) 35
2.3.4. Gel electrophoresis 38
2.3.5. Purification of PCR product 39
2.3.6. Cloning 39
2.3.7. Cleaved Amplified fragments Polymorphisms (CAPS) 40
2.4. Phylogenetic analyses 42
2.5. Data analyses 44
3. Results 45
3.1. Result Overview 45
3.2. Genotype results 46
3.2.1. Genotype results of CYCLOIDEA 46
3.2.1.1. Isolation of CYC like genes 46
3.2.1.2. Identity of isolated CYC like genes 47
3.2.1.3. Screen for segregation of CYC1A alleles 50
3.2.1.4. Screen for segregation of CYC1B alleles 53
3.2.2. Genotype results of RADIALIS 58
3.2.2.1. Isolation of RAD like genes 58
3.2.2.2. Identity of isolated RAD like genes 61
3.2.2.3. Screen for segregation of RAD1 alleles 64
3.2.2.4. Screen for segregation of RAD2 alleles 67
3.2.3. Genotype results of DIVARICATA 70
3.2.3.1. Isolation of DIV like genes 70
3.2.3.2. Identity of isolated DIV like genes 71
3.2.3.3. Screen for segregation of DIV1 alleles 74
3.2.3.4. Screen for segregation of DIV2 alleles 76
3.2.4. Genotype results of MYBML (MYB MIXTA LIKE) 79
3.2.4.1. Isolation of MYBML genes 79
3.2.4.2. Identity of isolated MYBML genes 81
3.2.4.3. Screen for segregation of MYBML2 alleles 84
3.3. Data analyses 86
3.3.1. Morphological data analyses 86
3.3.1.1. Correlations between pairs of floral traits 86
3.3.1.2. Cluster analysis of floral traits 88
3.3.2. Genotype data analyses 89
3.3.2.1. Most genes but CYC1A and MYBML2 follow Mendelism 89
3.3.2.2. Two linkage groups were found. 91
3.3.2.3. Associations between floral trait and gene locus 91
4. Discussion 94
4.1. Homologs of CYC, RAD, DIV, and MYBML2 are involved in the phenotypic variation of pollination-related floral traits 94
4.2. CYC1A/MYBML2 linkage group controlled the diameter of the insect chamber 95
4.3. To separate the individual effects of CYC1A and MYBML2 needs further study 96
4.4. CYC/MYBML2 linkage group is also found in Antirrhinum 96
4.5. Zygomorphy genes not only promote floral diversification through the establishment of zygomorphy but also through their effects on the pollination syndrome differentiation 97
Reference 99
Appendices 105
Appendix 1 Sequences obtained in this study 105
Appendix 1.1 CYC sequences 105
Appendix 1.2 RAD sequences 111
Appendix 1.3 DIV sequence 117
Appendix 1.4 MYBML sequence 122
Appendix 2 GenBank accession numbers of sequences used in phylogenetic analysis and tree statistics for phylogenies 127
Appendix 3 Genotypes for F2 plants 130
Appendix 4 Morphological data from F2 plants 135

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