Arabidopsis EID1 E3 ubiquitin ligase regulates acquired thermotolerance by modulating HSBP translocation

Climate change is causing a rapid increase in global average temperatures and more frequent heatwaves, posing serious threats to agricultural production and global biodiversity. In response to heat stress (HS), plants can develop acquired thermotolerance (AT) by initiating a heat shock response (HSR) after mild HS priming, thereby enhancing their ability to withstand subsequent later lethal HS events. Central to this process are the HEAT SHOCK FACTORs (HSFs), which form trimeric complexes and activate the expression of HEAT SHOCK PROTEINs (HSPs) and other HSFs to maintain proper protein and cellular functionality. After heat stress subsides, the HSFs activities can be modulated to attenuate the negative effects of HSR during the heat. The SHOCK FACTOR BINDING PROTEIN (HSBP) is a conserved microprotein that plays a prominent role in modulating HSF activities. HSBP can translocate from the cytoplasm into the nucleus during heat stress to directly interact with HSFs and prevent the formation of HSF timers. However, the mechanism that regulates the HSBP cytoplasmic-nuclear shuttling remains unclear. Here, we identified an F-box E3 ubiquitin ligase, EMPFINDLICHER IM DUNKELROTEN LICHT 1 (EID1), whose mutant form shows reduced thermotolerance in AT. We showed that EID1 interacts with HSBP to modulate HSBP cytoplasm-nuclear localization during heat stress, possibly through modulating the K41 of HSBP. The decreased thermotolerance in the eid1 mutant can be explained by alterations of some HSPs expression caused by the mis-localization of HSBP. This finding provided a novel example of E3 ubiquitin-mediated regulation of heat stress in plants.