NPR1 (P93002) Review Notes

Gene Overview

NPR1 is a master transcriptional regulator of systemic acquired resistance (SAR) in Arabidopsis. It functions as a salicylic acid (SA)-binding transcription cofactor.

Key Functional Evidence

Molecular Function - CORE

1. Transcription coregulator activity (GO:0003712) - Well-supported by multiple IDA/IMP studies [PMID:26269953, PMID:35545668]. NPR1 bridges TGA transcription factors to activate defense genes.

2. Salicylic acid binding (GO:1901149) - Direct biochemical evidence PMID:32788727. This is essential for NPR1 activation.

3. Zinc ion binding (GO:0008270) - Structural evidence from UniProt showing C2HC zinc finger motif critical for TGA interaction.

Biological Process - CORE

1. Systemic acquired resistance, salicylic acid mediated signaling pathway (GO:0009862) - The central function of NPR1, well-documented [PMID:17172357, PMID:11607555, PMID:12615947, etc.]

2. Regulation of systemic acquired resistance (GO:0010112) - Supported PMID:9002272

3. Defense response to bacterium (GO:0042742) - Well-supported [PMID:22699612, PMID:26269953]

4. Defense response to fungus (GO:0050832) - Supported PMID:17513501

5. Regulation of jasmonic acid mediated signaling pathway (GO:2000022) - NPR1 negatively regulates JA signaling PMID:12615947

6. Regulation of salicylic acid mediated signaling pathway (GO:2000031) - Supported PMID:12615947

Cellular Component

1. Nucleus (GO:0005634) - Multiple IDA studies showing nuclear localization after SA treatment [PMID:11148282, PMID:10662863, PMID:26269953]

2. Cytoplasm (GO:0005737) - IDA evidence for cytoplasmic localization in uninduced state [PMID:10662863, PMID:26269953]

3. Nuclear body (GO:0016604) - IDA evidence for sumoylated NPR1 in nuclear bodies PMID:26269953

4. RNA polymerase II transcription regulator complex (GO:0090575) - Evidence for complex with TGA factors PMID:12084833

Annotations to REMOVE or MODIFY

1. Protein binding (GO:0005515) - Multiple IPI annotations. This is uninformative and should be REMOVED per curation guidelines. The specific interacting partners are documented but the generic "protein binding" term doesn't tell us about function.

2. Defense response (GO:0006952) - Too general, MODIFY to more specific terms (defense response to bacterium, fungus)

3. Metal ion binding (GO:0046872) - Too general, already have zinc ion binding which is more specific

4. Innate immune response (GO:0045087) - Somewhat redundant with SAR, but could keep as non-core

5. Regulation of defense response (GO:0031347) - Too general, have more specific terms

Non-Core Functions (Pleiotropic)

• Response to heat (GO:0009408)
• Response to hypoxia (GO:0001666)
• Response to wounding (GO:0009611)
• Response to insect (GO:0009625)
• Extracellular ATP signaling (GO:0106167)
• Induced systemic resistance (GO:0009682)

These are all real but represent context-dependent or downstream effects rather than core NPR1 function.

Post-translational Modifications

• Phosphorylation at Ser-11, Ser-15, Ser-55, Ser-59
• Sumoylation (by SUMO3)
• Ubiquitination and proteasomal degradation
• S-nitrosylation at Cys-156
• Redox regulation via Cys-82/Cys-216 disulfide bonds

References

All PMIDs referenced are from the GOA file and UniProt record.

2026-09-27: merged the duplicate P93002 review into NPR1

The notes above were written for the duplicate review in genes/ARATH/P93002/, which covered the same protein (P93002). That folder has been retired and the review now lives here. After the merge, some of the notes' earlier framing no longer holds:

• SA binding is not treated as core. The notes above describe NPR1 as an "SA-binding transcription cofactor", and P93002 had salicylic acid binding as ACCEPT and core. The merged review keeps NPR1's MARK_AS_OVER_ANNOTATED instead. NPR1 binds SA only weakly PMID:32788727, and the receptor role belongs to NPR3/NPR4.
• Protein binding rows are split by partner. Rows whose partner is a transcription factor NPR1 coregulates are MODIFY → transcription coregulator activity: the TGA factors (coactivation) and WRKY70 (corepression by unmodified NPR1 at W-boxes PMID:26269953). The other partner rows are REMOVE under the GO:0005515 policy: NIMINs, NPR2/3/4, CUL3A, SUMO3, and interactome hits.
• Zinc ion binding is no longer a core MF. The notes above list zinc ion binding (GO:0008270) as core. The refreshed GOA no longer carries the GO:0008270 or GO:0046872 rows, and the merged review does not adopt zinc binding as a core function. The BTB zinc-finger motif is structural (it mediates BTB-ankyrin contact and oligomerization), not a separable molecular function.
• Negative regulation of defense response (IMP, PMID:16732289) is UNDECIDED. The cached record is abstract-only.