Title: Cullin 3 Plant E3 Ligases: A Perspective on Improving Agricultural Traits by Controlling Protein Stability

Hanjo Hellmann

Washington State University, USA


Dr Hellmann studied biology at the Technical University in Kaiserslautern, Germany. He started his PhD thesis in the group of Prof. Wolf Bernd Frommer in Berlin, Germany, on sugar and amino acid signal transduction, and received his PhD degree in 1997. He went for two years to the group of Prof. Mark Estelle, University of Texas at Austin, USA, as a postdoctoral researcher to work on auxin and plant E3 ligases. In 2002 he started his own group as an Assistant Professor at the Freie University in Berlin, Germany, with a focus on plant E3 ligases as well as on steps that control vitamin B6 biosynthesis in plants. In 2007 he moved to Washington State University, Pullman, USA, and was promoted to Associate Professor in 2013. He has published more than 45 articles reaching an h-index of 28.


Plant development depends on a complex and flexible regulatory network that integrates environmental cues with specific developmental programs.  A mechanism that provides plants with the ability to quickly and precisely respond is given by the ubiquitin-proteasome pathway. Within the pathway, E3 ligases are key regulators that recognize specific substrate proteins and mark them for degradation through the 26S proteasome. A particular class of E3 ligases, CRL3BPM, is composed of a scaffolding protein, Cullin3 (CUL3), and substrate adaptor proteins that contain a MATH-BTB/POZ domain (BPM). Arabidopsis thaliana encodes for six BPM (BPM1 to 6) and two CUL3 (CUL3a and 3b) proteins. Here we show that CRL3BPM E3 ligases are widely involved in transcriptional processes by affecting the stability of members of major transcription factor families in Arabidopsis. As a consequence, these E3 ligases alter diverse processes such as fatty acid biosynthesis, flowering time point control, and abiotic stress tolerance.  Our work establishes CRL3BPM E3 ligase as a major regulatory tool plant can use to facilitate controlled gene expression through specific protein degradation: a mechanism that allows plants a high degree of flexibility to quickly modulate their physiological and developmental processes as needed.