Current Research Interests

The main areas of interest of the laboratory are: 

1. The cytokinin response pathway

Cytokinins are essential plant hormones that control numerous aspects of plant development, including agriculturally important traits such as shoot branching, seed yield, leaf and flower senescence, drought stress tolerance, and disease resistance. We aim to better understand how cytokinin signaling works and how it controls plant growth.

2. Isolation of flavonoids using titanium dioxide (TiO2) nanoparticles

Flavonoids have become a major focus of attention because of their many health benefits. Recent years have also seen renewed interest in natural dyes, many of which are flavonoids. Currently, flavonoids are isolated from plants using preparative biochemical techniques that allow ample time for chemical modifications of in planta-existing flavonoids and that complicate downstream analyses of flavonoid activities. We have developed a rapid nanoparticle-based approach for flavonoid isolation from intact plants that yields nanoconjugates that can be used for bio-delivery of flavonoids. The method is sustainable because plants survive the treatment and can be reused after a recovery period. Our main goal is to understand, optimize, and broaden the scope of the nanoparticle-based isolation of plant flavonoids.

3. Oxidative stress tolerance in tobacco

TSNAs are carcinogenic chemicals that accumulate during the curing of tobacco leaves. Oxidative stress is caused by the formation of free radicals, such as peroxide or superoxide ions, which are thought to be important contributors to the TSNA formation process.

Selected Publications

• T. E. Shull, J. Kurepa and J. Smalle (2016). Cytokinin signaling promotes differential stability of type-B ARRs. Plant Signaling & Behavior 11(4).
• J. Kurepa, Y. Li and J. Smalle (2014). Cytokinin signaling stabilizes the response activator ARR1. The Plant Journal 78, 157-168.
• J. Kurepa, Y. Li, S.E. Perry and J. Smalle (2014). Ectopic expression of the phosphomimic mutant version of Arabidopsis response regulator 1 promotes a constitutive cytokinin response phenotype. BMC Plant Biology 14: 28.
• J. Kurepa, R. Nakabayashi, T. Paunesku, M. Suzuki, K. Saito, G.E. Woloschak and J. Smalle (2014). Direct isolation of flavonoids from plants using ultra-small anatase TiO2 nanoparticles. The Plant Journal 77, 443-453.
• C.A. Falaschetti, T. Paunesku, J. Kurepa, D. Nanavati, S.S. Chou, M. De, M. Song, J.T. Jang, A. Wu, V.P. Dravid, J. Cheon, J. Smalle and G.E. Woloschak (2013). Negatively Charged Metal Oxide Nanoparticles Interact with the 20S Proteasome and Differentially Modulate Its Biologic Functional Effects. ACS Nano 7, 7759–7772.
•  J. Kurepa, Y. Li and J. Smalle (2013). Reversion of the Arabidopsis rpn12a-1 exon-trap mutation by an intragenic suppressor that weakens the chimeric 5’ splice site (2013). F1000Research 2:60.
• J. Kurepa, Y. Li and J. Smalle (2013). Proteasome-dependent proteolysis has a critical role in fine-tuning the feedback inhibition of cytokinin signaling. Plant Signaling & Behavior8 (3).
• Y. Li, J. Kurepa and J. Smalle (2013). AXR1 promotes the cytokinin response by facilitating
• S. Wang, J. Kurepa, T. Hashimoto and J. Smalle (2011). Salt stress-induced disassembly of Arabidopsis cortical microtubule arrays involves 26S proteasome-dependent degradation of SPIRAL1. The Plant Cell 23, 3412-3427.
• J. Kurepa and J. Smalle (2011). Assaying transcription factor stability. Methods Mol Biol. 754, 219-234.
• S. Wang, J. Kurepa and J. Smalle (2011).Ultra-small TiO(2) nanoparticles disrupt microtubular networks in Arabidopsis thaliana. Plant Cell Environ. 34, 811-820.
• J. Kurepa, T. Paunesku, S. Vogt, H. Arora, B.M. Rabatic, J. Lu, M.B. Wanzer, G.E. Woloschak and J. Smalle (2010). Uptake and distribution of ultra-small anatase TiO2 Alizarin red S nanoconjugates in Arabidopsis thaliana. Nano Letters 10, 2296-2302.
• J. Kurepa, C. Karangwa, L. Sfichi Duke and J. Smalle (2010). Arabidopsis sensitivity to protein synthesis inhibitors depends on 26S proteasome activity. Plant Cell Reports 29, 249-259.
• S. Wang, J. Kurepa and J. Smalle (2009). Arabidopsis RPN1a is a non-essential 26S proteasome subunit isoform required for optimal plant growth and stress responses. Plant & Cell Physiology 50, 1721-1725.
• J. Kurepa, S. Wang, Y. Li, D. Zaitlin, A. J. Pierce and J. Smalle (2009). Loss of 26S proteasome function leads to increased cell size and decreased cell number in Arabidopsis shoot organs. Plant Physiology 150, 178-189.