BRI1 and BAK1 Canonical Distribution in Plasma Membrane Is HSP90 Dependent

Unveiling HSP40/60/70/90/100 gene families and abiotic stress response in Jerusalem artichoke

Heat shock proteins (HSPs) are essential for plant growth, development, and stress adaptation. However, their roles in Jerusalem artichoke are largely unexplored. Using bioinformatics, we classified 143 HSP genes into distinct families: HSP40 (82 genes), HSP60 (22 genes), HSP70 (29 genes), HSP90 (6 genes), and HSP100 (4 genes). Our analysis covered their traits, evolution, and structures. Using RNA-seq data, we uncovered unique expression patterns of these HSP genes across growth stages and tissues. Notably, HSP40, HSP60, HSP70, HSP90, and HSP100 families each had specific roles. We also studied how these gene families responded to various stresses, from extreme temperatures to drought and salinity, revealing intricate expression dynamics. Remarkably, HSP40 showed remarkable flexibility, while HSP60, HSP70, HSP90, and HSP100 responded specifically to stress types. Moreover, our analysis unveiled significant correlations between gene pairs under stress, implying cooperative interactions. qRT-PCR validation underscored the significance of particular genes such as HtHSP60-7, HtHSP90-5, HtHSP100-2, and HtHSP100-3 in responding to stress. In summary, our study advances the understanding of how HSP gene families collectively manage stresses in Jerusalem artichoke. This provides insights into specific gene functions and broader plant stress responses.

APRF1 Interactome Reveals HSP90 as a New Player in the Complex That Epigenetically Regulates Flowering Time in Arabidopsis thaliana

WD40 repeat proteins (WDRs) are present in all eukaryotes and include members that are implicated in numerous cellular activities. They act as scaffold proteins and thus as molecular "hubs" for protein-protein interactions, which mediate the assembly of multifunctional complexes that regulate key developmental processes in Arabidopsis thaliana, such as flowering time, hormonal signaling, and stress responses. Despite their importance, many aspects of their putative functions have not been elucidated yet. Here, we show that the late-flowering phenotype of the anthesis promoting factor 1 (aprf1) mutants is temperature-dependent and can be suppressed when plants are grown under mild heat stress conditions. To gain further insight into the mechanism of APRF1 function, we employed a co-immunoprecipitation (Co-IP) approach to identify its interaction partners. We provide the first interactome of APRF1, which includes proteins that are localized in several subcellular compartments and are implicated in diverse cellular functions. The dual nucleocytoplasmic localization of ARRF1, which was validated through the interaction of APRF1 with HEAT SHOCK PROTEIN 1 (HSP90.1) in the nucleus and with HSP90.2 in the cytoplasm, indicates a dynamic and versatile involvement of APRF1 in multiple biological processes. The specific interaction of APRF1 with the chaperon HSP90.1 in the nucleus expands our knowledge regarding the epigenetic regulation of flowering time in A. thaliana and further suggests the existence of a delicate thermoregulated mechanism during anthesis.

GA-Mediated Disruption of RGA/BZR1 Complex Requires HSP90 to Promote Hypocotyl Elongation

Circuitries of signaling pathways integrate distinct hormonal and environmental signals, and influence development in plants. While a crosstalk between brassinosteroid (BR) and gibberellin (GA) signaling pathways has recently been established, little is known about other components engaged in the integration of the two pathways. Here, we provide supporting evidence for the role of HSP90 (HEAT SHOCK PROTEIN 90) in regulating the interplay of the GA and BR signaling pathways to control hypocotyl elongation of etiolated seedlings in Arabidopsis. Both pharmacological and genetic depletion of HSP90 alter the expression of GA biosynthesis and catabolism genes. Major components of the GA pathway, like RGA (REPRESSOR of ga1-3) and GAI (GA-INSENSITIVE) DELLA proteins, have been identified as physically interacting with HSP90. Interestingly, GA-promoted DELLA degradation depends on the ATPase activity of HSP90, and inhibition of HSP90 function stabilizes the DELLA/BZR1 (BRASSINAZOLE-RESISTANT 1) complex, modifying the expression of downstream transcriptional targets. Our results collectively reveal that HSP90, through physical interactions with DELLA proteins and BZR1, modulates DELLA abundance and regulates the expression of BZR1-dependent transcriptional targets to promote plant growth.