Date of Award
Dianella DH Howarth
Richard RS Stalter
Rachel RZ Zufferery
Campanulaceae, with roughly 2,400 species, is divided into five subfamilies, in part, by differences in their floral orientation and symmetry, with broad transitions between radial and bilateral floral symmetry. The Hawaiian lobelioids in the Campanulaceae is the largest endemic clade of Hawaiian angiosperms, and they have long been viewed as one of the most spectacular examples of an adaptive radiation in plants. In the first part of our study, we focus on Clermontia, which is one of the largest genera of Hawaiian lobelioids, employing variable low-copy nuclear gene sequences to determine their phylogenetic relationships. We use intron regions from four separate copies of DIVRICATA (DIV), as well as variable regions of two Pentatricopeptide Repeat (PPR) genes, to construct a phylogenetic history of Hawaiian Clermontia and highlight patterns of frequent hybridization across the group. In the second part of our study, we aim to clarify the CYCLOIDEA-like gene duplication and expression patterns across Campanulaceae. We identified all three CamCYC paralogs from across Campanulaceae. We show that gene duplication is most common in CamCYC2, specifically in the bilaterally symmetrical Lobelioideae, which is in line with hypotheses of CYC2-like gene function in the core eudicots. However, in bilaterally symmetrical Cyphioideae, we detected CamCYC3 genes, but no CamCYC2 genes in this clade, suggesting that CamCYC3 genes might be involved in the development of bilaterally symmetrical flowers in this clade, instead of CamCYC2. To examine how tightly correlated the expression patterns of the CYC-like genes is with changes in flower morphology, we utilized qRT-PCR to determine CamCYC2 gene expression patterns in four species of bilaterally symmetrical Lobelioideae. The expression patterns of CamCYC2 genes was like other core eudicots species, with restriction of expression to the dorsal zone of the flower in bilateral symmetrical flowers. In Lobelioideae, with resupinate flowers, both CamCYC2A and CamCYC2B are highly expressed in the ventral petals. These ventral petals correspond to the dorsal side of the flower, suggesting conservation of dorsal identity in these upside down flowers. Additionally, individual copies of CamCYC2 genes show slightly different expression levels in different petals, suggesting possible subfunctionalization between these copies.
Tong, Jingjing, "Evolution and Flower Shape from the Hawaiian Lobelioids to the Campanulaceae" (2021). Theses and Dissertations. 183.
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