Abstract
The plant circadian clock regulates multiple developmental and physiological events that occur at specific times and seasons. As many of the currently known clock proteins and clock-associated regulators are transcription factors, analyzing molecular events in the nuclei is crucial. In addition, long-time course analyses of protein abundance and interactions are often required to assess the role of the circadian clock on clock-regulated phenomena. Here we introduce a simple procedure to prepare nuclear-enriched tissues, which we routinely use to study time-resolved accumulation changes in low-abundance nuclear proteins (i.e., transcription factors). In addition to measuring changes in abundance, investigating the protein-protein interaction dynamics at specific times of day or under certain environmental conditions is needed for plant chronobiology studies. Therefore, we also present our co-immunoprecipitation method for studying diurnal/circadian protein-protein interactions, tailored to nuclear-localized proteins in Arabidopsis and tobacco.