Date of Award

2023

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Life Sciences

First Advisor

Jeanmaire Molina

Committee Chair and Members

Jeanmaire Molina, Chair

Fatma Abo

Joseph Morin

Keywords

Arabidopsis, Germination pathway, Holoparasitic, Rafflesia, Strigolactones, Transcriptome

Abstract

Rafflesia (Rafflesiaceae) produces the largest flowers in the world but has no stems, roots, or leaves. It is a holoparasitic angiosperm that derives all its nutrients from its host vine, Tetrastigma. All species are also threatened with extinction, but propagating it has been incredibly challenging. Its germination from seed has never been observed. The thesis aims to reconstruct the germination pathway of Rafflesia from its published seed transcriptome to gain insight into its molecular genetics and understand what germination genes can be stimulated to facilitate infection of its host for ex-situ propagation. The published seed transcriptome of Rafflesia speciosa was annotated. These were then bioinformatically compared to the seed germination pathway genes in the model photosynthetic plant Arabidopsis (Brassicaceae) and in another parasitic plant, Striga (Orobanchaceae), to determine if there are similar genes conserved, especially the Strigolactones-responsive gene which promotes Striga germination in response to hormones called strigolactones. The assembled Rafflesia speciosa seed transcriptome contained more than 123,000 transcripts. Out of more than 123,000 de novo assembled transcripts, 7025 with blast hits were mapped and annotated. Among these, genes involved in abscisic acid, auxin, brassinosteroids, cytokinin, and ethylene signalling were detected in Rafflesia, in common with those in Arabidopsis. Still, no Strigolactones-responsive genes were detected in Rafflesia. This study showed that some germination signalling genes are conserved between Rafflesia and Arabidopsis but not with another parasitic plant. This suggests that strigolactones will not be useful in stimulating Rafflesia germination for propagation attempts.

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