Part I Evolution and Population Genetics of Self-Incompatibility
1 New Insights on Heterostyly: Comparative Biology, Ecology
and Genetics ................................................. 3
S.C.H. Barrett and J.S. Shore
1.1 Introduction ................................................ 4
1.2 Comparative Biology and Evolutionary History of
Heterostyly ................................................. 6
1.2.1 Phylogeny Reconstruction and Character Evolution ..... 7
1.3 Function and Reproductive Ecology of Heterostyly ........... 10
1.3.1 Function of Heterostyly ............................. 10
1.3.2 Floral Morph Ratios and Reproductive Success ........ 12
1.4 Inheritance of Heterostyly and the Supergene Model ......... 14
1.4.1 Inheritance of Distyly and Tristyly ................. 14
1.4.2 Supergene Model ..................................... 15
1.4.3 Mutational Analyses and the Study of Genetic
Variants ............................................ 19
1.5 Molecular Genetics ......................................... 19
1.5.1 Theoretical Models and Predictions .................. 20
1.5.2 Protein Profiles .................................... 22
1.5.3 mRNA Expression ..................................... 22
1.5.4 Genetic Localization ................................ 23
1.6 Concluding Remarks ......................................... 25
References ...................................................... 26
2 Genetic and Environmental Causes and Evolutionary Consequences
of Variations in Self-Fertility in Self Incompatible Species .... 33
S.V. Good-Avila, J.I. Mena-Alí, and A.G. Stephenson
2.1 Introduction ............................................... 34
2.2 Genetics of Self-Fertility ................................. 35
2.2.1 Mutations Affecting the S-locus ..................... 36
2.2.2 Unlinked Modifiers of SI ............................ 37
2.2.3 Plasticity in Self-Fertility ........................ 40
2.2.4 Summary of Genetics of Self-Fertility ............... 41
2.3 Fate of Self-Fertility Genes ............................... 42
2.3.1 Conditions for Stable Polymorphisms ................. 43
2.3.2 Summary and Conclusions Concerning Stable
Polymorphisms ....................................... 45
References ...................................................... 47
3 On the Evolutionary Modification of Self-Incompatibility:
Implications of Partial Clonality for Allelic Diversity and
Genealogical Structure .......................................... 53
M. Vallejo-Marín and M.K. Uyenoyama
3.1 Introduction ............................................... 54
3.2 Mating System Dynamics ..................................... 55
3.2.1 Relative Transition Rates ........................... 55
3.2.2 Multiple Origins of SC in Arabidopsis ............... 55
3.2.3 Modified Forms of SI ................................ 56
3.3 S-Locus Evolution Under Partial Clonality .................. 57
3.3.1 Diffusion Approximation ............................. 57
3.3.2 S-Allele Number and Frequency ....................... 60
3.3.3 Age of the Root ..................................... 62
3.4 Discussion ................................................. 65
3.4.1 Clonality in the Solanaceae ......................... 65
3.4.2 Evolutionary Stability of Partial SI ................ 65
3.4.3 Paradoxical Effects on Mating Systems ............... 66
3.5 Conclusions ................................................ 67
Appendix 1: Diffusion Equation Approximation .................... 68
Appendix 2: Simulations ......................................... 69
References ...................................................... 69
4 Evolution and Phylogeny of Self-Incompatibility Systems in
Angiosperms ..................................................... 73
A.M. Allen and S.J. Hiscock
4.1 Introduction ............................................... 74
4.1.1 Diversity of SI Systems in Angiosperms .............. 75
4.1.2 Evolutionary Origin(s) of SI Systems ................ 76
4.2 Was Self-Incompatibility Present in the First
Angiosperms? ............................................... 77
4.2.1 Self-Incompatibility in Basal Angiosperms ........... 78
4.2.2 Self-Incompatibility in the Monocots ................ 80
4.3 Phylogenetic Distribution of SI Systems .................... 81
4.3.1 Late-Acting Ovarian Self Incompatibility (OSI) ...... 84
4.3.2 Gametophytic Self-Incompatibility (GSI) ............. 86
4.3.3 Sporophytic Self-Incompatibility (SSI) .............. 88
4.4 The Relationship Between GSI and SSI ....................... 89
4.5 Discussion ................................................. 91
References ...................................................... 95
5 What Genealogies of S-alleles Tell Us .......................... 103
J.R. Kohn
5.1 Introduction .............................................. 104
5.2 Long-Term Demographic Information from the S-locus ........ 105
5.3 Implications of Shared Ancestral Polymorphism ............. 108
5.3.1 Tracing the History of Mating System Change ........ 108
5.3.2 Diversification Rate Differences and Character
State Reconstruction ............................... 110
5.4 The Pace of New Allele Formation .......................... 11l
5.5 Remaining Issues of S-RNase Evolution ..................... 112
5.6 Pollen Specificity Genes .................................. 114
5.7 Conclusions ............................................... 117
References ..................................................... 117
6 Self-Incompatibility and Evolution of Mating Systems in the
Brassicaceae ................................................... 123
S. Sherman-Broyles and J.B. Nasrallah
6.1 Introduction .............................................. 124
6.2 Structural and Sequence Diversification of S-locus
Haplotypes and Their Recognition Genes .................... 125
6.2.1 Conserved and Diverged Features of the S-locus ..... 127
6.2.2 Intra-Specific Structural Heteromorphism and
Sequence Polymorphism: Suppressed Recombination
and Maintenance of SRK-SCR Linkage ................. 128
6.2.3 Diversification of the S-locus Genes and the SI
Recognition Repertoire ............................. 130
6.3 Evolutionary Switches from Self-Incompatibility to Self-
Fertility ................................................. 135
6.3.1 Molecular Genetics of Switches to Self-Fertility ... 136
6.3.2 Breakdown of SI by Disruption of S-locus Gene
Expression in Inter-Specific Hybrids ............... 137
6.3.3 The Case of Self-Fertility in A. thaliana .......... 138
6.4 Future Prospects .......................................... 142
References ..................................................... 142
Part II Molecular and Cell Biology of Self-Incompatibility
Systems
7 Milestones Identifying Self-Incompatibility Genes in Brassica
Species: From Old Stories to New Findings ...................... 151
M. Watanabe, G. Suzuki, and S. Takayama
7.1 Self-Incompatibility as an Agriculturally Important
Trait ..................................................... 152
7.2 The First Milestone: Bateman's Idea for Sporophytic
Control of the S-locus .................................... 154
7.3 The Second Milestone: Identification of SLG by Using
IEF ....................................................... 155
7.4 The Third Milestone: Identification of SRK, the Female
S Determinant Gene ........................................ 156
7.5 The Fourth Milestone: Functional Evidences of SRK in SI ... 157
7.6 The Fifth Milestone: Establishment of Bioassay System ..... 158
7.7 The Sixth Milestone: Identification of SP11/SCR, the
Male S Determinant Gene ................................... 159
7.8 After Identifying the SI Genes and Future Milestones ...... 160
7.8.1 Demonstrating Physical Interaction Between SRK
and SP11/SCR ....................................... 160
7.8.2 Downstream of the Interaction: Identifying
Components and Mechanisms Involved in Mediating
the Rejection of Self Pollen ....................... 162
7.8.3 Molecular Mechanisms of Dominance Relationships .... 163
7.8.4 Evolution of SI Genes .............................. 164
7.9 Prospects ................................................. 165
References ..................................................... 166
8 'Self' Pollen Rejection Through the Intersection of Two
Cellular Pathways in the Brassicaceae: Self-Incompatibility
and the Compatible Pollen Response ............................. 173
M.A. Samuel, D. Yee, K.E. Haasen, and D.R. Goring
8.1 Introduction .............................................. 174
8.2 The Early Stages of Compatible Pollen-Stigma
Interactions in the Brassicaceae .......................... 175
8.2.1 Pollen Capture and Adhesion ........................ 175
8.2.2 Pollen Hydration ................................... 176
8.2.3 Pollen Germination and Pollen Tube Penetration ..... 178
8.3 The SI Response Causes Pollen Arrest at the Stigmatic
Surface ................................................... 179
8.3.1 The S Receptor Kinase Activates a Cellular
Signalling Pathway in the Stigmatic Papilla to
Trigger Self Pollen Rejection ...................... 179
8.3.2 The M Locus Protein Kinase acts Together with the
S Receptor Kinase to Promote SI .................... 180
8.3.3 The SRK Kinase Domain can Interact with a Range
of Intracellular Proteins .......................... 181
8.3.4 Thioredoxin h Inhibits SRK Activity in the
Absence of Self Pollen ............................. 182
8.3.5 ARC1 Functions Downstream of SRK to Promote SI ..... 182
8.3.6 BnExo70Al is a Potential Substrate for ARC1 and
is Required for Compatible Pollen-Stigma
Interactions ....................................... 184
8.3.7 Endomembrane Changes in the Stigmatic Papillae
Following Compatible and Self-Incompatible
Pollinations in the Brassicaceae ................... 185
8.4 Conclusions and Prospects ................................. 186
References ..................................................... 187
9 Molecular Biology of S-RNase-Based Self-Incompatibility ........ 193
Y. Zhang and Y. Xue
9.1 Introduction .............................................. 194
9.2 S-RNase Determines S-Specificity in Pistil ................ 196
9.2.1 Isolation and Identification of S-RNase as the
Pistil S ........................................... 196
9.2.2 S-RNase Sequence Features and the Specificity
Determinant ........................................ 196
9.2.3 The Role of S-RNase: A Cytotoxin Specifically
Inhibits Self Pollen ............................... 198
9.3 F-Box Proteins Determine S-Specificity in Pollen .......... 199
9.3.1 Clues from Pollen-Part Self Compatible Mutants ..... 199
9.3.2 Isolation of the Pollen SI Determinant, SLF/SFB .... 200
9.3.3 Sequence Analysis of SLFs and SFBs ................. 201
9.3.4 Identification of SLF as the Pollen S .............. 201
9.3.5 SFBs from Rosaceae Likely Represent Another Class
of F-Box Genes ..................................... 202
9.4 Other Genes That Modulate the SI Response ................. 203
9.4.1 The Pistil Modifier Factors ........................ 203
9.4.2 The Pollen Modifier Factors ........................ 204
9.5 Molecular Mechanisms for S-RNase-based SI ................. 205
9.5.1 Pollen S, the Positive or Negative Regulator of
S-RNase? Clues from Genetic Evidence ............... 205
9.5.2 The Fate of S-RNases: S-RNase Restriction is
Likely to Involve Ubiquitination ................... 206
9.5.3 Future Perspectives ................................ 208
References ..................................................... 210
10 Comparing Models for S-RNase-Based Self-Incompatibility ........ 217
B. McClure
10.1 The Biology of S-RNase-Based SI ........................... 218
10.1.1 Genetic Breakdown .................................. 218
10.2 S-RNase and S-locus F-box Proteins ........................ 219
10.2.1 S-RNase Structure and Specificity .................. 219
10.2.2 S-locus F-Box Genes ................................ 221
10.3 Non-S-Specific Genes ...................................... 222
10.3.1 HT Genes ........................................... 223
10.3.2 S-RNase Binding Proteins in the Transmitting
Tract Extracellular Matrix ......................... 224
10.3.3 Non-S-Specific Factors in Pollen ................... 226
10.4 Comparing Models for S-RNase-Based SI ..................... 227
10.4.1 How do Compatible Pollen Tubes Resist S-RNase
Cytotoxicity? ...................................... 227
10.4.2 Is There a Separate Mechanism in the Rosaceae? ..... 227
10.4.3 Inhibiting S-RNase Enzyme Activity ................. 228
10.4.4 S-RNase Degradation ................................ 228
10.4.5 S-RNase Compartmentalisation ....................... 231
References ..................................................... 233
11 Self-Incompatibility in Papaver Rhoeas: Progress in
Understanding Mechanisms Involved in Regulating Self-
Incompatibility in Papaver ..................................... 237
V.E. Franklin-Tong
11.1 Introduction .............................................. 238
11.1.1 Genetics and Cell Biology of Self-Incompatibility
in Papaver ......................................... 238
11.1.2 How Studies on Self-Incompatibility in Papaver
Started ............................................ 239
11.1.3 The Papaver in Vitro SI System ..................... 241
11.2 S Proteins Determine S-Specificity in the Pistil .......... 242
11.2.1 Identification of Pistil S-locus Components ........ 242
11.2.2 Pistil S-Protein Sequence Information and
Residues Required for Function ..................... 243
11.3 Identification of the Pollen S-Determinant ................ 243
11.4 Mechanisms Involved in SI in the Papaver System ........... 244
11.4.1 Calcium Signalling Mediates Papaver SI ............. 244
11.4.2 A Role for Soluble Inorganic Pyrophosphatases
(sPPases) in Papaver SI ............................ 245
11.4.3 Alterations to the Actin Cytoskeleton are
Triggered by Papaver SI ............................ 246
11.4.4 SI Triggers Programmed Cell Death .................. 247
11.5 An Overall Model for Mechanisms Involved in Regulating
SI in Papaver ............................................. 251
11.5.1 A Contrast to the S-RNase System and Brassica SI
Systems ........................................... 253
11.6 Future Perspectives ....................................... 254
References ..................................................... 255
12 Molecular Genetics of Sporophytic Self-Incompatibility in
Ipomoea, a Member of the Convolvulaceae ........................ 259
Y. Kowyama, T. Tsuchiya, and K. Kakeda
12.1 Introduction .............................................. 260
12.2 Sexual Reproduction in the Genus Ipomoea .................. 261
12.3 Genetics of Self-Incompatibility in Ipomoea ............... 261
12.4 Stigma-Specific Proteins .................................. 263
12.5 Physical Size of the S-locus .............................. 264
12.6 Genomic Organisation of the S-locus ....................... 266
12.7 S-locus Genes in Ipomoea .................................. 268
12.8 Diversity of the SI Systems ............................... 270
References ..................................................... 271
13 Self-Incompatibility in the Grasses ............................ 275
P. Langridge and U. Baumann
13.1 Introduction .............................................. 276
13.2 Genetic Control of SI in the Grasses ...................... 277
13.2.1 Features of the S-Z System ......................... 278
13.2.2 The Third Locus 'T' ................................ 279
13.2.3 Mechanism of Action of S- and Z-Gene Products ...... 280
13.3 Approaches and Progress in Cloning S and Z ................ 280
13.3.1 Reverse Genetics ................................... 281
13.3.2 Forward Genetics ................................... 281
13.4 Conclusions ............................................... 284
References ..................................................... 285
14 Heteromorphic Self-Incompatibility in Primula: Twenty-First
Century Tools Promise to Unravel a Classic Nineteenth Century
Model System ................................................... 289
A. McCubbin
14.1 Introduction .............................................. 290
14.2 Floral Characteristics of the Mating Types of Primula ..... 291
14.2.1 Style .............................................. 292
14.2.2 Stigma ............................................. 292
14.2.3 Corolla Mouth Size ................................. 292
14.2.4 Anthers ............................................ 293
14.2.5 Pollen ............................................. 293
14.2.6 Self-Incompatibility Specificity ................... 293
14.3 Functions of Heteromorphic Characters ..................... 293
14.4 Physiological Nature of SI ................................ 295
14.4.1 Site of Operation .................................. 295
14.4.2 Candidate Molecules in the Operation of
Heteromorphic SI ................................... 297
14.5 The Primula S-Locus ....................................... 297
14.5.1 Genetic Structure .................................. 297
14.5.2 Location and Size of the S-locus ................... 301
14.5.3 Allelic Dominance .................................. 301
14.6 Floral Development ........................................ 302
14.7 Molecular Genetic Characterisation of the Primula
S-locus: Current Status ................................... 303
14.8 Conclusions and Future Prospects .......................... 305
References ..................................................... 306
Index ............................................................. 309
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