Mitonuclear Conflict in the F1 Hybrid Coral ‘Acropora prolifera’
Open Access
- Author:
- Manzano, Bryan
- Area of Honors:
- Biology
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Iliana B Baums, Thesis Supervisor
Benoit A Dayrat, Thesis Honors Advisor - Keywords:
- Mitonuclear conflict
Acroporid coral
Hybridization
Coexpression Network Analysis
WGCNA
Oxidative Phosphorylation - Abstract:
- The Caribbean’s two most important reef building corals, elkhorn coral (Acropora palmata) and staghorn coral (A. cervicornis), cross to form the first generation (F1) hybrid coral “A. prolifera". This F1 hybrid could mitigate damages to reefs due to elevated temperatures from climate change. One problem with using this hybrid coral within a conservation context is the potential for hybrid breakdown in later generations. In fact, “A. prolifera” is thought to be sterile since F2 hybrids of “A. prolifera” are not found on the reef. One mechanism leading to hybrid breakdown is termed mitonuclear conflict, where incompatibility between mitochondrially-encoded genes and nuclear-encoded genes negatively impact oxidative phosphorylation, limit efficient mitochondrial function, and lead to apoptosis. In this study, it was hypothesized that mitonuclear conflict causes hybrid breakdown in the F2 generation. A co-expression network analysis approach was used to test if mtDNA genes in the hybrid are differentially coexpressed when compared to its parental taxa, the result of which would suggest that the hybrid could have an altered oxidative phosphorylation (OXPHOS) pathway and thus experience mitonuclear conflict and hybrid breakdown. In this experiment, four genets of each taxon were collected in Belize and transferred to an in situ common garden. After six months, samples were taken and their RNA was sequenced. It was found that mtDNA genes were not tightly coexpressed as suggested by low values of a measure known as topological overlap measure, a finding that is contradictory to the normally rigid co-expression of critical mtDNA in the OXPHOS pathway. Clustering analyses also suggested that all mtDNA genes differed in co-expression, a finding that contradicts other studies. These results could be explained by technical errors during data analysis. Alternatively, A. palmata may have been stressed in the common garden environment and thus had altered gene expression leading to a disruption in the co-expression of mtDNA genes. Additional analyses are required to distinguish between these possibilities before mitonuclear conflict can be ruled out as a cause of acroporid coral hybrid breakdown in F2 and later generations in the wild.