Could be involved in splicing and/or processing of chloroplast RNA's. ADP-ribosylated by the Pseudomonas syringae type III effector HopU1. ADP-ribosylation reduces the ability of the protein to bind RNA. Phosphorylated on tyrosine residues after treatment with abscisic acid (ABA). Phosphorylation may reduce the ability of the protein to bind RNA.