Dissertation
Unraveling the S-locus: Characterization of the S-genes in distylous Turnera (Passifloraceae)
Washington State University
Doctor of Philosophy (PhD), Washington State University
01/2022
DOI:
https://doi.org/10.7273/000004427
Handle:
https://hdl.handle.net/2376/124862
Abstract
Distyly is an Angiosperm reproductive system controlled by a supergene called the S-locus. Distylous individuals exhibit two morphs, the S- and L-morphs that exhibit self-incompatibility (SI) and reciprocal placement of the stamen and pistil. The S-locus contains three or more loci inherited as a single unit in a Mendelian fashion. Traditionally, the S-morph was believed to be heterozygous for the S-locus and the L-morph homozygous recessive. However, recent advances in molecular genetics have shown this is not the case in distylous species of Primula. Instead, the S-morph is hemizygous for the S-locus. In this work, we investigated the molecular genetic basis of distyly in Turnera (Passifloraceae).
We assembled the S-locus of Turnera subulata and described its hemizygosity. Annotation of the S-locus showed it is composed of three S-genes; YUC6, which determines male mating-type by auxin (IAA) biosynthesis; SPH1, which likely determines filament length; and BAHD, which determines both female mat-ing-type and pistil length via brassinosteroid inactivation.
As the presence of the S-genes likely causes changes to overall gene expression in the S-morph, we next investigated differentially expressed genes between the two floral morphs using RNAseq. This analysis provided additional evidence supporting the hypothesized roles of YUC6 and BAHD. Furthermore, the results suggest that the basis of SI is a complementation of high auxin and low brassinosteroid levels in the pollen of the S-morph and low auxin and high brassinosteroid levels in the stigma of the L-morph (the same scenario in inverse fertilization).
Next, we showed that BAHD confers female mating-type but that brassinosteroid is not solely responsible for the recognition and rejection of self-pollen, but that other factors are likely involved. We also formally showed that YUC6 is the male determinant factor via knocking down the expression of YUC6 in Turnera joelii using an antisense construct. YUC6 also determines pollen size dimorphism. Finally, we annotated the genome of T. subulata and identified members of the three S-gene families. This analysis suggests that the S-genes were acquired independently in a step-by-step manner. Overall, this work represents the first investigation into the molecular genetic basis of distyly in the genus Turnera.
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Details
- Title
- Unraveling the S-locus: Characterization of the S-genes in distylous Turnera (Passifloraceae)
- Creators
- Paige M Henning
- Contributors
- Andrew G McCubbin (Advisor)Michael M Neff (Committee Member)Eric H Roalson (Committee Member)Joel S Shore (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Biological Sciences, School of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 256
- Identifiers
- 99900883240001842
- Language
- English
- Resource Type
- Dissertation