Cynthia K. Holland

Scholarship/Creative Work

About half of all modern pharmaceuticals are derived from or inspired by compounds found in nature, and many of these molecules are still extracted from plants. Plants typically produce these chemicals as toxins to deter herbivores, like insects and animals, but the enzymes that they use to produce these natural products remain largely unknown. The Holland lab uses molecular biology and protein biochemistry techniques to identify and characterize the biosynthetic pathways of commercially and pharmaceutically relevant plant metabolites.

NSF-funded research on anthranilate metabolism

To defend themselves against herbivores, plants such as grape, maize, citrus, and strawberry emit a volatile called methyl anthranilate, which attracts parasitic insects and acts as a natural bird deterrent. While at least ten plant families produce methyl anthranilate, all plants synthesize the precursor, anthranilate, as an intermediate in the biosynthesis of the amino acid tryptophan (Trp), which is essential for plant growth and development. Some plants siphon anthranilate away from the Trp pathway by methylating it, forming the volatile O-methyl anthranilate, while the Citrus family generates N-methyl anthranilate as a precursor to toxic acridone alkaloids. The goal of this research is to understand how plants regulate anthranilate metabolism at the interface between amino acid synthesis and defense metabolism. Since methyl anthranilate is used commercially as a grape flavoring agent in the food and beverage industry and as an anti-avian spray for fields and crops, knowledge gained from these experiments may have implications in biotechnology and agriculture.

Cardenolide biosynthesis in wallflower

Cardenolides are a chemically diverse group of natural products that act as allosteric inhibitors of Na⁺,K⁺-ATPase, an essential membrane ion transporter that is found in almost all animal cells. The pharmaceutical cardenolide digoxin is used to treat heart arrhythmias and is on the World Health Organization’s list of essential medicines, but the cardenolide biosynthetic pathway has yet to be investigated. Using a recently sequenced genome for a cardenolide-producing species of wallflower (Erysimum cheiranthoides), our current efforts are focused on identifying and characterizing candidate genes using genomics, protein biochemistry, and analytical chemistry techniques.

Current Lab Members:

• Ellia Chiang ’25
• Cameron Darnell ’25
• Tajis Lyn ’25
• Owen Patrick ’25
• Aracely Watson ’25
• Marie Brockhoff ’26
• Chris Flores ’26

Former Thesis Students:

• Michael Fallon ’24, Research Technician in the Kleinstiver lab, Harvard Medical School
• Nina van der Velde ’24, MPhil Candidate, Cambridge University
• Hisham Tadfie ’23, NSF Graduate Research Fellow in the Nett lab, Harvard University
• Miriam Li ’23, Research Associate at the Innovative Protein Institute
• Rebecca Brody ’22, Medical Student, University of Pennsylvania
• Madeline Dyke ‘21.5, Co-founder + Operations Director of Climate Changemakers
• Jessica Hem ’21, Graduate Student, University of North Carolina

Selected publications:

Michael Fallon ’24*, Hisham Tadfie ’23*, Aracely Watson ’25*, Madeline Dyke ‘21.5, Chris Flores ’26, Cook NC, Fei Z, and Holland CK (2024) Molecular basis of one-step methyl anthranilate biosynthesis in grapes, sweet orange, and maize. The Plant Journal. *Equal contribution.

Miriam Li ’23, Hisham Tadfie ’23, Cameron Darnell ’25, and Holland CK (2023) Biochemical investigation of the tryptophan biosynthetic enzyme anthranilate phosphoribosyltransferase in plants.  Journal of Biological Chemistry 299(10): 105197.

Holland CK and Hisham Tadfie ’23 (2022) A structure-guided computational screening approach for predicting plant enzyme-metabolite interactions. In Methods in Enzymology: Biochemical Pathways and Environmental Responses in Plants Part A, Vol. 676: 71-101.

Lopez-Nieves S, El-Azaz J, Men Y, Holland CK, Feng T, Brockington S, Jez JM, Maeda H. (2022) Two independently evolved natural mutations additively deregulate TyrA enzymes and boost tyrosine production in planta. The Plant Journal 109(4): 844-55.

Züst T, Strickler SR, Powell AF, Mabry ME, An H, Mirzaei M, York T, Holland CK, Kumar P, Erb M, Petschenka G, Gómez J-M, Perfectti F, Müller C, Pires JC, Mueller LA, Jander G (2020) Independent evolution of ancestral and novel defenses in a genus of toxic plants (Erysimum, Brassicaceae). eLife 9:e51712

Schenck CA, Holland CK, Schneider MR, Men Y, Lee SG, Jez JM, Maeda HA (2017) Molecular basis of the evolution of alternative tyrosine biosynthesis pathways in plants.  Nature Chemical Biology 13, 1029-35.