Extreme weather conditions associated with climate change affect many aspects of plant and animal life, including the response to infectious diseases. Production of salicylic acid (SA), a central plant defence hormone1–3, is particularly vulnerable to suppression by short periods of hot weather above the normal plant growth temperature range via an unknown mechanism4–7. Here we show that suppression of SA production in Arabidopsis thaliana at 28 °C is independent of PHYTOCHROME B8,9 (phyB) and EARLY FLOWERING 310 (ELF3), which regulate thermo-responsive plant growth and development. Instead, we found that formation of GUANYLATE BINDING PROTEIN-LIKE 3 (GBPL3) defence-activated biomolecular condensates11 (GDACs) was reduced at the higher growth temperature. The altered GDAC formation in vivo is linked to impaired recruitment of GBPL3 and SA-associated Mediator subunits to the promoters of CBP60g and SARD1, which encode master immune transcription factors. Unlike many other SA signalling components, including the SA receptor and biosynthetic genes, optimized CBP60g expression was sufficient to broadly restore SA production, basal immunity and effector-triggered immunity at the elevated growth temperature without significant growth trade-offs. CBP60g family transcription factors are widely conserved in plants12. These results have implications for safeguarding the plant immune system as well as understanding the concept of the plant–pathogen–environment disease triangle and the emergence of new disease epidemics in a warming climate.

Really Interesting New Gene (RING) E3 ubiquitin ligases have been implicated in cellular responses to the stress hormone abscisic acid (ABA) as well as to environmental stresses in higher plants. Here, an ABA-insensitive RING protein3 (atairp3) loss-of-function mutant line in Arabidopsis (Arabidopsis thaliana) was isolated due to its hyposensitivity to ABA during its germination stage as compared with wildtype plants. AtAIRP3 contains a single C3HC4-type RING motif, a putative myristoylation site, and a domain associated with RING2 (DAR2) domain. Unexpectedly, AtAIRP3 was identified as LOSS OF GDU2 (LOG2), which was recently shown to participate in an amino acid export system via interaction with GLUTAMINE DUMPER1. Thus, AtAIRP3 was renamed as AtAIRP3/LOG2. Transcript levels of AtAIRP3/LOG2 were up-regulated by drought, high salinity, and ABA, suggesting a role for this factor in abiotic stress responses. The atairp3/log2-2 knockout mutant and 35S:AtAIRP3-RNAi knockdown transgenic plants displayed impaired ABAmediated seed germination and stomata closure. Cosuppression and complementation studies further supported a positive role for AtAIRP3/LOG2 in ABA responses. Suppression of AtAIRP3/LOG2 resulted in marked hypersensitive phenotypes toward high salinity and water deficit relative to wild-type plants. These results suggest that Arabidopsis RING E3 AtAIRP3/LOG2 is a positive regulator of the ABA-mediated drought and salt stress tolerance mechanism. Using yeast (Saccharomyces cerevisiae) two-hybrid, in vitro, and in vivo immunoprecipitation, cell-free protein degradation, and in vitro ubiquitination assays, RESPONSIVE TO DEHYDRATION21 was identified as a substrate protein of AtAIRP3/LOG2. Collectively, our data suggest that AtAIRP3/LOG2 plays dual functions in ABA-mediated drought stress responses and in an amino acid export pathway in Arabidopsis.

AtAIRP2 is a cytosolic RING-type E3 ubiquitin ligase that positively regulates an abscisic acid (ABA) response in Arabidopsis (Arabidopsis thaliana). Yeast two-hybrid screening using AtAIRP2 as bait identified ATP1 (AtAIRP2 Target Protein1) as a substrate of AtAIRP2. ATP1 was found to be identical to SDIRIP1, which was reported recently to be a negative factor in ABA signaling and a target protein of the RING E3 ligase SDIR1. Accordingly, ATP1 was renamed ATP1/SDIRIP1. A specific interaction between AtAIRP2 and ATP1/SDIRIP1 and ubiquitination of ATP1/SDIRIP1 by AtAIRP2 were demonstrated in vitro and in planta. The turnover of ATP1/SDIRIP1 was regulated by AtAIRP2 in cell-free degradation and protoplast cotransfection assays. The ABA-mediated germination assay of 35S:ATP1/SDIRIP1-RNAi/atairp2 double mutant progeny revealed that ATP1/ SDIRIP1 acts downstream of AtAIRP2. AtAIRP2 and SDIR1 reciprocally complemented the ABA-and salt-insensitive germination phenotypes of sdir1 and atairp2 mutants, respectively, indicating their combinatory roles in seed germination. Subcellular localization and bimolecular fluorescence complementation experiments in the presence of MG132, a 26S proteasome inhibitor, showed that AtAIRP2 and ATP1/SDIRIP1 were colocalized to the cytosolic spherical body, which lies in close proximity to the nucleus, in tobacco (Nicotiana benthamiana) leaf cells. The 26S proteasome subunits RPN12a and RPT1 and the molecular chaperones HSP70 and HSP101 were colocalized to these discrete punctae-like structures. These results raised the possibility that AtAIRP2 and ATP1/SDIRIP1 interact in the cytosolic spherical compartment. Collectively, our data suggest that the down-regulation of ATP1/SDIRIP1 by AtAIRP2 and SDIR1 RING E3 ubiquitin ligases is critical for ABA and highsalinity responses during germination in Arabidopsis.