PP2A mediates phosphorylation events during shade avoidance response in Arabidopsis

Many of shade-intolerant or sun-loving plants grown in close proximity experience a change in light quality and quantity, which leads to transcriptional reprogramming and consequently shade avoidance syndrome (SAS). Despite the importance of phosphorylation-dependent signaling for cellular physiology, the phosphorylation events during SAS are largely unknown. Here, we carried out a survey of shade-regulated protein phosphorylation events by a large-scale mass spectrometry-based quantitative phosphoproteomics approach. The activity of protein phosphatase 2A (PP2A) was specifically activated by shade treatment. Thereinto, shade de-phosphorlated a group of basic leucine zipper (bZIP) transcription factor by PP2A-b’ηθγζ. This study elucidates a previously unidentified mechanism by which the PP2A-bZIPs regulatory module integrates shade signal, and thus uncovers a phosphorylation strategy for the rapid response to changes of environment.