| Functional aspect | Key findings | Evidence type | Quantitative/statistical details | Primary source (author, year, journal) with URL |
|---|---|---|---|---|
| Molecular function | AtHSP90.1 (At5g52640; UniProt P27323) is the cytosolic Hsp90 isoform in Arabidopsis with canonical Hsp90 architecture: N-terminal ATPase domain, middle client-binding region, and C-terminal dimerization/MEEVD motif for TPR co-chaperones; functions as an ATP-dependent molecular chaperone/scaffold for client protein maturation and stability (pqac-00000000, pqac-00000002) | Biochemistry, genetics | Domain-level mapping showed RAR1 binds the N-terminal ATPase-containing half; geldanamycin used at 10–50 μM in immune assays (pqac-00000000) | Takahashi et al., 2003, *PNAS*. https://doi.org/10.1073/pnas.2033934100 |
| Localization | Evidence supports AtHSP90.1 as a cytosolic HSP90; Arabidopsis has four cytosolic HSP90 isoforms, with other family members targeted to chloroplast, mitochondrion, or ER, distinguishing AtHSP90.1 from organellar paralogs (pqac-00000002, pqac-00000003, pqac-00000007) | Genetics, review/inference | No explicit localization percentage reported in cited excerpts; localization is consistently described as cytosolic/cytoplasmic (pqac-00000002, pqac-00000003) | Takahashi et al., 2003, *PNAS*. https://doi.org/10.1073/pnas.2033934100; Kahrizi et al., 2025, *bioRxiv*. https://doi.org/10.1101/2025.06.21.660849 |
| Key partners / co-chaperones | AtHSP90.1 physically interacts with RAR1 and SGT1; RAR1 binds the N-terminal ATPase region, while SGT1 engages HSP90 through TPR/CS-related features. These interactions define a plant HSP90–SGT1–RAR1 immune chaperone system for NLR stability/function (pqac-00000000, pqac-00000001, pqac-00000002) | Biochemistry, genetics | Two interaction modes proposed for SGT1 with HSP90; deletion mapping identified HSP90 interaction regions including C-terminal MEEVD-dependent and N-terminal contacts (pqac-00000000) | Takahashi et al., 2003, *PNAS*. https://doi.org/10.1073/pnas.2033934100 |
| Pathways / biological processes: immunity | AtHSP90.1 is essential for full RPS2-mediated disease resistance and contributes to RPM1 resistance; it supports hypersensitive response and likely stabilizes NLR immune receptors/complexes (pqac-00000001, pqac-00000002, pqac-00000005) | Genetics, pharmacology, plant pathology | Geldanamycin caused ~5–6-fold higher *Pst* avrRpt2 bacterial titer at 1 dpi and ~10-fold at 2 dpi; ~6-fold increase for avrRpm1 at 2 dpi. *athsp90.1* mutants showed 5–20-fold more bacterial growth by 3 dpi; significance reported at P < 0.05 (pqac-00000005, pqac-00000001) | Takahashi et al., 2003, *PNAS*. https://doi.org/10.1073/pnas.2033934100 |
| Pathways / biological processes: chloroplast preprotein targeting | Cytosolic HSP90, together with HOP and FKBP cochaperones, associates with freshly synthesized chloroplast preproteins and helps route a subset to the TOC import machinery, linking AtHSP90.1-like cytosolic HSP90 activity to post-translational plastid protein targeting (pqac-00000006) | Biochemistry, co-IP, pull-down | “More than half” of tested preproteins used the HSP90+HSP70 route; 12 tested preproteins specifically bound HSP90; TaHOP identified in pull-down with 9.9% sequence coverage (pqac-00000006) | Fellerer et al., 2011, *Molecular Plant*. https://doi.org/10.1093/mp/ssr037 |
| Pathways / biological processes: heat stress / thermotolerance | AtHSP90.1 participates in heat-stress responses with FKBP co-chaperones ROF1/ROF2 and the HsfA2 network; literature cited in 2023 work indicates ROF1 interacts with HSP90.1 to modulate thermotolerance and small HSP accumulation, and HSP90.1/ROF1 are targets of NBR1-mediated selective autophagy in heat-stress memory (pqac-00000004, pqac-00000014) | Proteomics, genetics, review of primary studies | No direct fold-change for AtHSP90.1 in excerpt; rof1 mutants are heat sensitive after 45 °C challenge, whereas rof2 shows greater heat resistance; HSP90.1 listed among proteins enriched in rof1/rof2 double mutants (pqac-00000010, pqac-00000014) | Lefa et al., 2023, *ACS Omega*. https://doi.org/10.1021/acsomega.3c06773 |
| Pathways / biological processes: auxin transport / development (recent 2024) | 2024 work implicates HSP90.1 in development by stabilizing plasma-membrane ABCB auxin transporters through interaction with FKBP42/TWD1; HSP90 inhibition or mutation reduces ABCB abundance, perturbs polar auxin transport, increases root twisting, and alters root auxin distribution (pqac-00000011, pqac-00000012, pqac-00000013, pqac-00000017) | Biochemistry, pharmacology, genetics, proteomics | HSP90.1–TWD1 binding reported in low micromolar Kd range; 5 μM geldanamycin for 24 h reduced PM ABCB levels; TMT proteomics used n=4; root twisting quantified with n > 20; significance shown at P < 0.05 (pqac-00000011, pqac-00000012) | Geisler et al., 2024, *Research Square preprint*. https://doi.org/10.21203/rs.3.rs-4533687/v1 |
| Phenotypes / quantitative data | *athsp90.1* loss-of-function mutants show no obvious morphology under normal growth but are compromised in effector-triggered immunity; pharmacological HSP90 inhibition similarly impairs HR and resistance. This supports a specialized stress/immune buffering role rather than a strong constitutive developmental defect (pqac-00000005, pqac-00000008, pqac-00000009) | Genetics, pharmacology | Pathogen assays used *Pst* inocula of 10^5–10^7 cfu/mL; bacterial growth measured immediately and 3 dpi; chlorosis increased by 6 dpi in mutants; figure evidence documents CFU/cm² increases in mutants and geldanamycin-treated plants (pqac-00000005, pqac-00000008) | Takahashi et al., 2003, *PNAS*. https://doi.org/10.1073/pnas.2033934100 |
| Recent 2023–2024 findings | 2023 proteomics linked HSP90-1 abundance to ROF-FKBP-dependent heat acclimation networks; 2024 studies/reviews extended HSP90.1 relevance to selective autophagy/heat recovery and to auxin-transporter stabilization, broadening its annotation beyond immunity alone (pqac-00000010, pqac-00000012, pqac-00000014) | Proteomics, systems biology, review, preprint | In rof datasets, HSP90-1 was differentially accumulated/enriched in double mutants; in auxin work, HSP90-dependent microsomal proteomics used 16-plex TMT and GDA 5 μM for 24 h (pqac-00000012, pqac-00000015) | Lefa et al., 2023, *ACS Omega*. https://doi.org/10.1021/acsomega.3c06773; Geisler et al., 2024, *Research Square preprint*. https://doi.org/10.21203/rs.3.rs-4533687/v1 |
| Applications / real-world relevance | AtHSP90.1 is a plausible target for engineering stress resilience and disease resistance, but also a cautionary node because HSP90 inhibition can suppress immunity and auxin-dependent development. Plant HSP90 biology is already used conceptually in chemical biology (geldanamycin/radicicol-class inhibition) and in crop stress-improvement strategies through chaperone/co-chaperone manipulation (pqac-00000005, pqac-00000006, pqac-00000012) | Pharmacology, translational inference | Practical perturbants include geldanamycin 5–50 μM depending on assay; recent work links HSP90-dependent proteostasis to developmental plasticity and thermotolerance pathways, making the system relevant for crop engineering (pqac-00000005, pqac-00000012) | Takahashi et al., 2003, *PNAS*. https://doi.org/10.1073/pnas.2033934100; Geisler et al., 2024, *Research Square preprint*. https://doi.org/10.21203/rs.3.rs-4533687/v1 |


*Table: This table summarizes functional annotation evidence for Arabidopsis thaliana HSP90-1/AtHSP90.1 (At5g52640; UniProt P27323), including molecular role, localization, interaction partners, pathways, phenotypes, and recent 2023–2024 findings. It is useful as a compact evidence map linking specific claims to experimental modalities, quantitative details, and source URLs.*