In plants and most eukaryotes, the ubiquitin proteasome pathway has been proven to be crucial for many developmental and regulatory processes. The pathway is a response mediator of various different signals which are perceived by cellular receptors and transduced within the cell. E3 ubiquitin ligases are the key players in this pathway and facilitate transfer of the ubiquitin moiety to substrate proteins, which are usually transcription factors, thereby controlling stability and activity of these proteins and their downstream target genes. Cullin proteins are a common core subunit of many E3 ligase complexes. My group’s main interest is in E3 ligases that contain cullins which have been demonstrated to participate in such important processes as embryo and organ development, phytohormone signal transduction, stress tolerance and light response. Ongoing goals in the group are the following:
(1) to unravel cellular and environmental conditions like phytohormones, heat stress, or light that lead to assembly of the different cullin based complexes within the cell
(2) to characterize organ and cell specific responses
(3) to identify substrate proteins that are degraded or modified by these E3 ligases
(4) to characterize signal transduction pathways activating the different cullin-based E3 ligases and
(5) to functionally describe gain- and loss-of-function mutants affected in E3 ligase subunits or substrate proteins.
Vitamin B6, or pyridoxine, is an important compound that mediates more than 100 biochemical reactions. Plants, fungi, and some bacteria can synthesize this vitamin, however in humans and other mammals it must be taken up from nutrients. Several important functions of this vitamin include alleviating oxidative stress in fungus and UV-light and salt stress in higher plants.
My group is interested in the final steps of vitamin B6 biosynthesis, which are catalyzed by two small protein families that assemble to higher-order protein complexes. Specifically, what mechanisms control activity of the protein complexes and how is this activity connected with stress tolerance in higher plants. Undergraduate students: Interested students are always welcome to do internships or BIO499 classes on selected topics to gain practical experiences in laboratory work. Graduate students: I am currently accepting graduate students. Please feel free to contact me if you are interested in joining the lab.
Mooney, S., Chen, L., Kühn, C., Navarre, D.A., Knowles, N.R., Hellmann, H. (2013) Genotype Specific Changes in Vitamin B6 Content and the PDX Family in Potato. BioMed Res Int Article ID 389723.
Chen, L., Lee, J.H., Weber, H., Tohge, T., Witt, S., Roje, S., Fernie, A.R., Hellmann, H. (2013) Arabidopsis BPM proteins function as substrate adaptors to a CUL3-based E3 ligase to affect fatty acid metabolism in plants. Plant Cell 25, 2253-2264.
Chen, L., and Hellmann, H. (2013) Plant E3 Ligases: Flexible Enzymes In A Sessile World. Mol Plant 10.1093/mp/sst005
Funck D., Clauss K., Frommer W.B., Hellmann H. (2012) The Arabidopsis CstF64-like RSR1/ESP1 protein participates in glucose signaling and flowering time control. Front. Plant. Physiol. 3, 80.
Fitzpatrick T.B., Basset G.J.C., Borel P., Carrari F., DellaPenna D., Fraser P.H., Hellmann H., Osorio S., Rothan C., Valpuesta V., Caris-Veyrat C., Fernie A.R. (2012) Vitamin deficiencies in humans: Can Plant Science help? Plant Cell, 24, 395-414.
Biedermann S., Mooney S., Hellmann H. (2011) Recognition and Repair Pathways of Damaged DNA in Higher Plants, Selected Topics in DNA Repair, Clark C. Chen (Ed.), InTech Publishing ISBN: 978-953-307-606-5.
Leasure C.D., Tong H.-Y., Hou X.-W., Shelton A., Minton M., Esquerra R., Roje S., Hellmann H., He Z.-H. (2011) root uv-b sensitive Mutants Are Suppressed by Specific Mutations in ASPARTATE AMINOTRANSFERASE2 and by Exogenous Vitamin B6. Mol. Plant 4, 759-770.
Leuendorf J.E., Osorio S., Szewczyk A., Fernie A.R., Hellmann H. (2010) Complex assembly and metabolic profiling of Arabidopsis thaliana plants overexpressing vitamin B6 biosynthesis proteins. Mol. Plant 3, 890-903.
Bernhardt A, Mooney S, Hellmann H. (2010) Arabidopsis DDB1a and DDB1b are critical for embryo development. Planta 232, 555-566.
Biedermann S. and Hellmann H. (2010) The DDB1a interacting proteins ATCSA-1 and DDB2 are critical factors for UV-B tolerance and genomic integrity in Arabidopsis thaliana. Plant J. 62, 404-415.
Mooney S., and Hellmann H. (2010) Vitamin B6: Killing two birds with one stone? Phytochemistry 71, 495-501.
Hellmann H., and Sutton Mooney (2010) Vitamin B6: A Molecule for Human Health? Molecules 15, 442-459.
Weber H., and Hellmann H. (2009) Arabidopsis thaliana BTB/POZ-MATH proteins interact with members of the ERF/AP2 transcription factor family. FEBS J. 22, 6624 – 6635.
Mooney S., Leuendorf J.E., Hendrickson C., Hellmann H. (2009) Vitamin B6: a long known compound of surprising complexity. Molecules 14, 329-351.
Lytovchenko A., Beleggia R., Schauer N., Isaacson T., Leuendorf J.E., Hellmann H., Rose J.K., Fernie A.R. (2009) Application of GC-MS for the detection of lipophilic compounds in diverse plant tissues. Plant Methods 5:4.