Global translational reprogramming is a fundamental layer of immune regulation in plants.

In the absence of specialized immune cells, the need for plants to reprogram transcription to transition from growth-related activities to defence is well understood. However, little is known about translational changes that occur during immune induction. Using ribosome footprinting, here we perform global translatome profiling on Arabidopsis exposed to the microbe-associated molecular pattern elf18. We find that during this pattern-triggered immunity, translation is tightly regulated and poorly correlated with transcription. Identification of genes with altered translational efficiency leads to the discovery of novel regulators of this immune response. Further investigation of these genes shows that messenger RNA sequence features are major determinants of the observed translational efficiency changes. In the 5' leader sequences of transcripts with increased translational efficiency, we find a highly enriched messenger RNA consensus sequence, R-motif, consisting of mostly purines. We show that R-motif regulates translation in response to pattern-triggered immunity induction through interaction with poly(A)-binding proteins. Therefore, this study provides not only strong evidence, but also a molecular mechanism, for global translational reprogramming during pattern-triggered immunity in plants.

Global translational induction during NLR-mediated immunity in plants is dynamically regulated by CDC123, an ATP-sensitive protein.

The recognition of pathogen effectors by their cognate nucleotide-binding leucine-rich repeat (NLR) receptors activates effector-triggered immunity (ETI) in plants. ETI is associated with correlated transcriptional and translational reprogramming and subsequent death of infected cells. Whether ETI-associated translation is actively regulated or passively driven by transcriptional dynamics remains unknown. In a genetic screen using a translational reporter, we identified CDC123, an ATP-grasp protein, as a key activator of ETI-associated translation and defense. During ETI, an increase in ATP concentration facilitates CDC123-mediated assembly of the eukaryotic translation initiation factor 2 (eIF2) complex. Because ATP is required for the activation of NLRs as well as the CDC123 function, we uncovered a possible mechanism by which the defense translatome is coordinately induced during NLR-mediated immunity. The conservation of the CDC123-mediated eIF2 assembly suggests its possible role in NLR-mediated immunity beyond plants.

Generating mammalian sirtuin tools for protein-interaction analysis.

The sirtuins are a family of NAD(+)-dependent deacylases with important effects on aging, cancer, and metabolism. Sirtuins exert their biological effects by catalyzing deacetylation and/or deacylation reactions in which Acyl groups are removed from lysine residues of specific proteins. A current challenge is to identify specific sirtuin target proteins against the high background of acetylated proteins recently identified by proteomic surveys. New evidence indicates that bona fide sirtuin substrate proteins form stable physical associations with their sirtuin regulator. Therefore, identification of sirtuin interacting proteins could be a useful aid in focusing the search for substrates. Described here is a method for identifying sirtuin protein interactors. Employing basic techniques of molecular cloning and immunochemistry, the method describes the generation of mammalian sirtuin protein expression plasmids and their use to overexpress and immunoprecipitate sirtuins with their interacting partners. Also described is the use of the Database for Annotation, Visualization, and Integrated Discovery for interpreting the sirtuin protein-interaction data obtained.