Author ORCID Identifier
https://orcid.org/0000-0001-9456-6002
Date Available
12-10-2026
Year of Publication
2025
Document Type
Doctoral Dissertation
Degree Name
Doctor of Philosophy (PhD)
College
Agriculture, Food and Environment
Department/School/Program
Plant and Soil Sciences
Faculty
Ling Yuan
Faculty
Arthur Hunt
Abstract
Since the dawn of humanity plant specialized metabolites have been utilized for their invaluable properties including health benefits, fragrances, poisons, spices, and medicine. The most valuable specialized metabolites are often produced in small quantities and command high prices. Understanding the intricate complexities of when and how the plant synthesizes these compounds is important for improving their production. Phytohormone signaling cascades, such as jasmonate (JA) activate or repress transcription factors (TF) controlling expression of specialized metabolite pathway genes. Key regulatory TFs that regulate specialized metabolite biosynthetic genes can be manipulated via the genetic engineering of plants to ultimately increase metabolite production.
The plant Mediator complex is a core component in the activation of gene expression. Conservation of the MED25 subunit between plant species, and its relation to JA signaling implicates this factor in regulation of specialized metabolism. MED25 is involved in the accumulation of the specialized metabolites anthocyanin and monoterpene indole alkaloids, but how it functions remains unknown. Characterization of MED25 in Arabidopsis revealed it interacts with the anthocyanin pathway transcription factor GL3, as well as the JAZ1 repressor. Characterization of MED25 in Catharanthus reveals MED25 interacts with the MIA pathway transcription factor MYC2, as well as the COI1 protein of the SCFCOI1 repression complex. Importantly, the interaction of JAZ1 with MED25 reveals a new mechanism by which JAZ proteins regulate gene expression, improving our understanding of JA signaling.
The bHLH family of transcription factors are known components of both JA signaling cascades and regulation of specialized metabolite biosynthesis pathway. The presence of target binding sites in promoters of several monoterpene indole alkaloids enzymes points to a significant role the serve in regulating biosynthesis of these compounds. A phylogenetic analysis was used to compare Arabidopsis and Catharanthus bHLH TFs families. A coexpression analysis was conducted to determine bHLH expression levels under jasmonic acid treatment, providing candidates for future characterization. Gene expression analysis identified MIA pathway genes effected by both JA and bHLH83 expression in Catharanthus. The data for our target TF bHLH83 suggests a conserved regulatory role within the network of TFs downstream of JA signaling cascades and the latter MIA pathway branches.
Due to public legal and social scrutiny regarding the use of GMO technology in crop production, new methods and approaches need to be introduced for formal innovation in the field of genetic engineering. This review will provide a comprehensive aggregate of future prospects and speculative analysis on potential experimental, as well as practical applications in the future engineering of non-GMO crops. The goals of this review include establishment of the groundwork for new ideas and approaches to provide innovative concepts for the field of genetic engineering and specialized metabolism.
Digital Object Identifier (DOI)
https://doi.org/10.13023/etd.2025.569
Recommended Citation
Singleton, Joshua J. Dr., "REGULATORY MECHANISMS OF SPECIALIZED METABOLISM IN CATHARANTHUS ROSEUS" (2025). Theses and Dissertations--Plant and Soil Sciences. 199.
https://uknowledge.uky.edu/pss_etds/199
