Date of Award

2023

Document Type

Thesis

Degree Name

Master of Science in Biology

Department

Life Sciences

First Advisor

Jeanmaire Molina

Committee Chair and Members

Jeanmaire Molina, Chair

Joseph Morin

Su-Hwan Kwak

Keywords

Arabidopsis, Rafflesia, Transcriptome

Abstract

The holoparasitic plant genus Rafflesia is of interest for producing the largest single flowers in the world, though efforts to conserve it have been challenging with not much success in ex situ propagation due to the little that we know of its biology. Further study and understanding of the growth of Rafflesia species is necessary in order to preserve these endangered plants. Due to its potentially long growth cycle, there is a definite difficulty in studying the growth cycle through observation alone. Transcriptomic study is one tool which can be used to understand how Rafflesia species change throughout different stages of growth. Using data from the NCBI SRA database, along with data from a recent study which is pending publication/review, the transcriptome of Rafflesia speciosa seed and Rafflesia cantleyi flower bud was obtained by De Novo assembly in Geneious Prime and processing in OmicsBox. The transcriptomes of Rafflesia seed and flower bud were compared to the transcriptomes of the seed and flower bud from Arabidopsis thaliana, respectively, to gain insights on transcriptome dynamics from seed to flower in a flowering non-photosynthetic parasite compared to a “typical” photosynthetic plant. The proportions of transcripts related to active pathways were compared across the different growth stages of Rafflesia and Arabidopsis and trends that conflict between these two were further investigated, e.g. higher proportion in Rafflesia seed than flower bud, with the inverse being true in Arabidopsis seed versus flower bud, and vice versa. These trends were explored and compared to literature about the growth of Arabidopsis thaliana, as well as what is known about the growth of other holoparasitic plants such as Orobanche and Striga. Some pathways in Rafflesia seed are of note, including increased gluconeogenesis processes in the seed compared to its flower, as well as the elevated “carbon fixation” processes, despite being nonphotosynthetic. Glutathione metabolism was also higher in the Rafflesia seed which may be related to amelioration of oxidative damage in the seed as the seed germinates in the host and counterattack its immune response. Transcripts for “starch and sucrose metabolism” were proportionally higher in the Rafflesia bud, which makes sense as it proceeds with floral development. Inverse trends were seen between Rafflesia and Arabidopsis in certain pathways such as increased gluconeogenesis in Rafflesia seed more than its flower bud, but the opposite was true for Arabidopsis, while there was increased transcription for RNA and lysine degradation, ubiquitin-mediated proteolysis, and plant hormone signal transduction in the Arabidopsis seed compared to its flower bud that was not the pattern observed in Rafflesia. The potential implications of these findings are discussed.

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