Dynamic ubiquitin signalling coordinates transcriptional reprogramming in plant immunity
Dynamic regulation of gene expression is vital for all organisms and enables them to respond to the ever-changing environment. Plant cells display dramatic reprogramming of the transcriptome in response to pathogen attack, ensuring prioritisation of immune responses over normal cellular functions. The immunizing hormone salicylic acid (SA) plays indispensable roles in this process, establishing long-lasting disease resistance against future pathogen attack. Chemical and genetic approaches that impinge on SA signalling have been developed to combat economically costly plant diseases that threaten future food security. However, these protection strategies are often environmentally unsustainable or have penalties on plant growth and yield. Understanding how SA reprograms the transcriptome to establish durable immunity will enable the urgent design of improved sustainable technologies for crop protection.    My team recently pioneered discoveries that demonstrate SA employs the small post-translational modifier, ubiquitin, to establish durable immunity. SA induces dynamic modification of regulatory proteins with ubiquitin chains of diverse linkage types, generating the potential to control their functions and activities. Understanding the relevance of distinct ubiquitin chain types and their protein targets is a major challenge and is only in its infancy in plants. The ‘UbRegulate’ project will reveal how SA-induced ubiquitin signalling: (i) engages the transcriptional machinery and reveal its potential for exploitation by agrichemical biology; (ii) avoids transcription-induced genome instability; (iii) orchestrates chromatin permissiveness to allow gene expression; and (iv) utilises diverse chain linkage types to establish durable, broad-spectrum immunity. In addition to advancing fundamental insights into dynamic ubiquitin signalling, this ambitious project will reveal how ubiquitin signalling can be harnessed to revolutionise plant protection strategies.