B.S., Biotechnology, Calvin College. Grand Rapids, MI.
Ph.D., Biochemistry and Molecular Biology, University of California, Riverside
Postdoc Fellow, University of Wisconsin, Madison
CMB 250 Introduction to Biotechnology
BIO 406 Cell and Molecular Biology Lab
CMB 505 Advanced Cellular Biology
CMB 610 Foundations in Biotechnology
Protein degradation mechanisms, signal transduction, phytohormone action.
One way in which organisms control cellular processes is by regulating the level of specific proteins within a cell through protein degradation. This process targets and eliminates specific proteins that need to be removed in order for eukaryotes to respond to developmental or environmental cues.
The most prolific protein degradation pathway in eukaryotes is the Ubiquitin/Proteasome System (UPS). This system uses a small polypeptide (ubiquitin) to tag proteins by enzymatically ligating active ubiqutin onto the target protein (ubiquitination). Once ubiquitinated, the target protein is sent to the proteasome where it is degraded.
I am particularly interested in how eukaryotic cells can target specific proteins for degradation during distinct cues, yet leave other proteins intact. I am investigating the role of specific multi-subunit complexes, called E3 ligases, that recognize and bind to the correct protein target, and subsequently ligate ubiquitin onto it. Although all eukaryotes use the UPS to degrade proteins, plants in particular, have evolved a multitude of E3 ligases to breakdown proteins at exact times, and use the UPS extensively in development and survival. My research focuses on how plants use the UPS to respond to hormones, and external signals.
Other topics I am interested in:
Phytohormone signal transduction pathways.
Light signal transduction and development in plants.
Christians MJ, Gingerich DJ, Hua Z, Lauer TD, Vierstra RD. The light-response BTB1 and BTB2 proteins assemble nuclear ubiquitin ligases that modify phytochrome B and D signaling in Arabidopsis. Plant Physiol. 2012 Sep;160(1):118-34. *Recommended by the faculty of 1000
Zheng X, Miller ND, Lewis DR, Christians MJ, Lee KH, Muday GK, Spalding EP, Vierstra RD. AUXIN UP-REGULATED F-BOX PROTEIN1 regulates the cross talk between auxin transport and cytokinin signaling during plant root growth. Plant Physiol. 2011 Aug;156(4):1878-93.
Christians MJ, Gingerich DJ, Hansen M, Binder BM, Kieber JJ, Vierstra RD. The BTB ubiquitin ligases ETO1, EOL1 and EOL2 act collectively to regulate ethylene biosynthesis in Arabidopsis by controlling type-2 ACC synthase levels. Plant J. 2009 Jan;57(2):332-45. *Featured Article
Christians MJ, Robles LM, Zeller SM, Larsen PB. The eer5 mutation, which affects a novel proteasome-related subunit, indicates a prominent role for the COP9 signalosome in resetting the ethylene-signaling pathway in Arabidopsis. Plant J. 2008 Aug;55(3):467-77.
Robles LM, Wampole JS, Christians MJ, Larsen PB. Arabidopsis enhanced ethylene response 4 encodes an EIN3-interacting TFIID transcription factor required for proper ethylene response, including ERF1 induction. J Exp Bot. 2007;58(10):2627-39.