FORGETTER2 protein phosphatase and phospholipase D modulate heat stress memory in Arabidopsis

Summary Plants can mitigate environmental stress conditions through acclimation. In the case of fluctuating stress conditions such as high temperatures, maintaining a stress memory enables a more efficient response upon recurring stress. In a genetic screen for Arabidopsis thaliana mutants impaired in the memory of heat stress (HS) we have isolated the FORGETTER2 (FGT2) gene which encodes a type 2C protein phosphatase (PP2C) of the D-clade. Mutants in fgt2 acquire thermotolerance normally; however, they are defective in the memory of HS. FGT2 interacts with phospholipase Dα2 (PLDα2), which is involved in metabolizing membrane phospholipids, and PLDα2 is also required for HS memory. In summary, we uncover a previously unknown component of HS memory and identify the FGT2 protein phosphatase and PLDα2 as crucial players, suggesting that phosphatidic acid-dependent signaling or membrane composition dynamics underlie HS memory