rice quantitative ubiquitome induced by PAMPs

To better understand the regulatory roles of ubiquitination in rice pattern-triggered immunity (PTI), we investigated the ubiquitome of rice seedlings after treatment with two pathogen-associated molecular patterns (PAMPs), the fungal-derived chitin or the bacterial-derived flg22, using label-free quantitative proteomics. In chitin-treated samples, 144 and 167 lysine-ubiquitination sites in 121 and 162 proteins, respectively, and in flg22-treated samples, 151 and 179 lysine-ubiquitination sites in 118 and 166 proteins, respectively, were identified showing increased and decreased ubiquitination, respectively. Bioinformatic analyses indicated diverse regulatory roles of these proteins. The ubiquitination level of many proteins involved in ubiquitination system, protein transportation, ligand recognition, membrane trafficking, and redox reactions showed significantly changes in response to the elicitor treatments. Notably, the ubiquitination levels of many enzymes in the phenylpropanoid metabolic pathway were up-regulated, indicating this pathway is tightly regulated by ubiquitination during rice PTI. Additionally, the ubiquitination levels of some key components in plant hormone signaling pathways were observed to be up- or down-regulated, suggesting ubiquitination may fine-tune hormone pathways for defense responses.