Quantitative proteomic profiling of Arabidopsis nuclei reveals accumulation of nucleolar proteins after a prolonged heat stress

Heat stress (HS) impacts the nuclear proteome and, subsequently, protein activities in the nucleoplasm and/or different nuclear compartments. In Arabidopsis thaliana, a short exposure to 37°C leads to the loss of the standard tripartite architecture of the nucleolus, the most prominent nuclear substructure, and, consequently, affects the assembly of ribosomes 1. Here, we report a quantitative label-free LC-MS/MS analysis to determine the nuclear proteome of Arabidopsis at 22ºC, HS (37ºC 4 and 24 hours), and a recovery phase. This analysis identified ten distinct groups of proteins based on their protein abundance in the nucleus before, during and after HS: the Early Group (EG), Late Group (LG), Transient Group (TG), Early Persistent Group (EPG), Late Persistent Group (LPG), Burst Group (BG), Early-Like Group (ELG), Late-Like Group (LLG), Transient-Like Group (TLG) and Continuous-Induced Group (CIG). Interestingly, the RNA Pol I subunit NRPA3 and other main nucleolar proteins – such as Nucleolin and Fibrillarin – were detected in the BG and CIG, suggesting that plants require increased nucleolar activity and likely ribosome assembly to restore protein synthesis after HS.