Subject Area

Biochemistry, Biological Sciences, General, Chemistry

Abstract

Light is a fundamental environmental cue that regulates growth, development, and circadian rhythms in fungi. In Trichoderma reesei, a filamentous fungus of industrial significance due to its cellulase production, light sensing coordinates both physiology and transcriptional regulation. Blue Light Receptor 1 (BLR1), a Light-Oxygen-Voltage (LOV) domain–containing photoreceptor and ortholog of Neurospora crassa White Collar 1 (WC1), plays a central role in these processes, yet its molecular mechanisms and interaction network remain incompletely understood. This dissertation investigates the structural and mechanistic activity of BLR1, with a focus on how the LOV domain mediates light-induced responses, how BLR1 participates in protein-protein interactions, and how it regulates transcription in concert with Blue Light Receptor 2 (BLR2) and Envoy (ENV1). The hypothesis is that BLR1 functions as the core photoreceptor of the Trichoderma reesei circadian system by forming light-dependent homodimers, interacting with BLR2 and ENV1 in heteromeric complexes analogous to WC1/WC2/VVD in N. crassa, and establishing conserved structural motifs critical for transcriptional regulation. vii To test this, a combination of biochemical, structural, and functional approaches was employed, including protein expression and purification, size exclusion chromatography to assess oligomerization, optogenetic assays to probe activation dynamics, sequence alignment, and structural modeling to identify conserved residues for mutational analysis, and comparative interaction assays with VVD homologs. The results demonstrate that BLR1 forms light induced homodimers, engages in heterodimeric interactions with ENV1 and VVD homologs across multiple species, and shows preliminary evidence for BLR1/BLR2 heterodimerization, with data also suggesting the existence of higher-order trimeric assemblies involving BLR1, ENV1, VVD, or BLR2. These findings position BLR1 as the central hub of the Trichoderma reesei light sensing system, paralleling the role of WC1 in N. crassa while revealing species specific structural and functional adaptations. By confirming conserved and novel protein:protein interactions, this work enhances understanding of fungal photoreception and circadian regulation and contributes to broader efforts to manipulate light signaling pathways for applications in industry, agriculture, and synthetic biology. Future studies resolving the structural basis of these complexes and mapping their transcriptional outputs in vivo will further elucidate BLR1’s role and advance both fundamental circadian biology and its biotechnological applications.

Degree Date

Fall 2025

Document Type

Dissertation

Degree Name

Ph.D.

Department

Chemistry

Advisor

Dr. Brian Zoltowski

Second Advisor

Dr. Alex Lippert

Third Advisor

Dr. John Buynak

Fourth Advisor

Dr. Jon Hibshman

Acknowledgements

I would like to thank my research advisor Dr. Brian Zoltowski for allowing a forensic scientist into his laboratory to grow and learn a whole new field. I would also like to thank my committee members, Dr. Alexander Lippert, Dr. John Buynak, and Dr. Jon Hibshman. I would like to thank my family, Ken, Linda, Ashlyn, and Kenton but in particular my mother for the continued support, encouragement, and insistence on never giving up. Her unshakable confidence in me kept me going even when I did not think I could. I could never have done it without her. She has truly been my pillar and biggest cheerleader in this journey. I would like to thank TaNeil for commiserating with me about the doctoral journey, supporting me through my meltdowns, and always listening and pointing me to God’s plan. I would like to thank Courtney for listening to my complaints, worries, tears and always encouraging me and building me up. I would like to thank my husband Eddie Valdez for the continued support, dinners, and late night encouragement. I would like to thank Lauren O’Donnel Griffin for her assistance in the lab and unwavering support. I would like to thank Julia Laura, and Eric Brinckman for their comradery in this crazy place. Finally, I would like to thank Southern Methodist University (SMU) and the National Institute for Health (NIH) for the funding that made this dissertation research and PhD program possible.

Number of Pages

280

Format

PDF

Creative Commons License

Creative Commons Attribution-Noncommercial 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 License

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