Processive ubiquitination controls NPR1 coactivator activity in plant immunity
S. SPOEL (1), J. Furniss (1), M. Skelly (1), H. Grey (1) (1) University of Edinburgh, United Kingdom

Gene expression plays a pivotal role in the development of eukaryotic cells and their response to the environment. Failure to precisely program cellular gene expression often has pathological or deleterious consequences. In plants, hormone-responsive transcriptional programs are controlled by nuclear E3 ubiquitin ligases that function as both hormone receptors and as transcription cofactors. The plant immune hormone salicylic acid (SA), involved in development of the broad-spectrum systemic immunity, is perceived by a nuclear Cullin3-RING ubiquitin ligase (CRL3), resulting in the reprogramming of thousands of genes to prioritize immune responses over normal cellular growth functions. SA-induced CRL3 ubiquitinates the indispensable transcription coactivator NPR1, resulting in its proteasome-mediated degradation. Surprisingly, turnover of NPR1 coactivator is necessary for the activation of its target genes, suggesting that transcription may require continuous delivery of fresh NPR1 coactivator to gene promoters. To better understand the role of ubiquitination in shaping NPR1-dependent transcriptional reprogramming, we used genetic and biochemical approaches to investigate a potential role for ubiquitin chain modifying enzymes. Our findings revealed that these enzymes are vital for appropriate NPR1-dependent immune gene expression, probably by modifying ubiquitin chains of both NPR1 and associated transcriptional regulators. Here we discuss how in development of broad-spectrum immunity, the concerted action of different ubiquitin chain modifying enzymes may establish a processive ubiquitin timer and amplifier for transcriptional activity of NPR1. This work was funded by The Royal Society, BBSRC, ERC and Bayer CropScience.

Abstract Number: C15-5, P18-701
Session Type: Concurrent