The protein modifier SUMO is critical for Arabidopsis shoot meristem maintenance at warmer ambient temperatures

Abstract

Short heat waves (>37{degrees}C) are extremely damaging to non-acclimated plants and their capacity to recover from heat stress is key for their survival. To acclimate, the HEAT SHOCK TRANSCRIPTION FACTOR A1 (HSFA1) subfamily activates a transcriptional response that resolves incurred damages. In contrast, little is known how plants acclimate to sustained non-detrimental warm periods at 27-28{degrees}C. Plants respond to this condition with a thermomorphogenesis response. In addition, HSFA1 is critical for plant survival during these warm periods. We find that SUMO, a protein modification whose conjugate levels rise sharply during acute heat stress in eukaryotes, is critical too for plant longevity during warm periods, in particular for normal shoot meristem development. The known SUMO ligases were not essential to endure these warm periods, alone or in combination. Thermo-lethality was also not seen when plants lacked certain SUMO proteases or when SUMO chain formation was blocked. The SUMO-dependent thermo-resilience was as well independent of the autoimmune phenotype of the SUMO mutants. As acquired thermotolerance was normal in the sumo1/2 knockdown mutant, our data thus reveal a role for SUMO in heat acclimation that differs from HSFA1 and SIZ1. We conclude that SUMO is critical for shoot meristem integrity during warm periods. HighlightThe protein modifier SUMO governs shoot meristem maintenance in Arabidopsis allowing sustained rosette development when plants endure a sustained warm non-detrimental period of 28 degrees Celsius.