Title Page
ABSTRACT
Contents
Introduction 11
1. Life cycle of C. elegans in natural habitat 12
2. Phoretic strategy for dispersal and survival of C. elegans 14
3. Previous studies on nictation behavior 16
4. From genes to behavior 17
5. Behavior diversity and plasticity at the gene-environment interface 19
Materials and Methods 21
Results and Discussions 34
Part I. Genetic basis of heritable variation in nictation behavior of C. elegans 35
1. Natural variation of nictation behavior and phoretic dispersal 36
2. Domestication effect on nictation behavior in laboratory N2 strain 51
Part II. Genetic basis of environmental plasticity in nictation behavior 88
1. Regulation of nictation behavior by TGF-β signaling 89
2. Rescue of nictation defect of TGF-β mutant by pheromone treatment and downregulation of cGMP signaling 97
Reference 115
국문초록 122
Table 1. Polymorphisms in nict-1 QTL between N2 and CB4856 genome. 78
Table 2. piRNA variation in nict-1 QTL between N2 and CB4856 genome. 83
Table 3. nict-1 QTL regulated differentially expressed genes (DEGs) 84
Table 4. Correlation study between nictation and reproduction in 11 wild isolates 86
Table 5. Relative fitness calculation of N2 and CB4856 nict-1 QTL. 87
Figure 1. Nictation fraction of 12 divergent wild isolates. 56
Figure 2. Histogram of normalized nictation fraction of 186 N2xCB4856... 57
Figure 3. nict-1 QTL mapping. 58
Figure 4. Nictation fraction of RIAILs by genotype at nict-1 QTL peak. 59
Figure 5. Fine mapping of the nict-1 QTL. 60
Figure 6. Dominance test of nict-1 QTL. 61
Figure 7. Genomic features of NIL-narrowed 73 kb nict-1 QTL interval. 62
Figure 8. Relative mRNA expression of 4 protein-coding genes in nict-1 QTL. 63
Figure 9. Genetic analysis for candidate genes in nict-1 QTL. 64
Figure 10. Involvement of Piwi Argonaute PRG-1 in regulation of nictation... 65
Figure 11. Model for the effect of piRNA variations on gene expression... 66
Figure 12. Volcano plot for global gene expression landscape. 67
Figure 13. Heat map of the two-way hierarchical clustering. 68
Figure 14. Diagram of nict-1 QTL regulated DEG. 69
Figure 15. Gene expression regulation by Piwi Argonaute PRG-1. 70
Figure 16. Fitness effect of nict-1 QTL on reproduction. 71
Figure 17. Experimental scheme of transmission competition assay. 72
Figure 18. Fitness effect of nict-1 QTL on phoretic dispersal 73
Figure 19. Correlation study between reproduction and nictation. 74
Figure 20. Nictation fraction of chromosome substitute strains (CSSs). 75
Figure 21. Nictation fraction of npr-1 introgressed near isogenic lines. 76
Figure 22. Nictation fraction of npr-1(ky13), flp-18(gk3063), flp-21(ok889). 77
Figure 23. Diagram of the DAF-7/TGF-β signaling pathway. 100
Figure 24. Regulation of nictation behavior by canonical DAF-7/TGF-β signaling... 101
Figure 25. Regulation of nictation behavior by neuroendocrinal DAF-7/TGF-β... 103
Figure 26. Experimental scheme of nictation assay on non-pathogenic OP50-... 105
Figure 27. Effect of feeding pathogenic PA14 on nictation. 106
Figure 28. Model for regulation of nictation behavior by TGF-β signaling pathway. 107
Figure 29. daf-7 suppressor screening scheme. 108
Figure 30. daf-7 suppressor screening result 109
Figure 31. Effect of pheromone treatment in daf-7(ok3125) mutant. 110
Figure 32. Volcano plot for gene expression analysis between pheromone... 111
Figure 33. Volume plot for gene expression analysis between pheromone treated... 112
Figure 34. GO analysis (Biological process) on DEGs between pheromone... 113
Figure 35. GO analysis (Molecular function) on DEGs between pheromone... 114