PLGG1 (AtLrgB; At1g32080; UniProtKB:Q9FVQ4) curation notes

Deep research could not be run in this environment (no provider API keys). These notes
are a manual literature summary built only from cached publications in publications/
and the UniProt record (PLGG1-uniprot.txt). No -deep-research-*.md file exists for
this gene.

Identity

• UniProt Q9FVQ4, "Plastidal glycolate/glycerate translocator 1, chloroplastic"
  (AltName AtLrgB); 512 aa precursor; transit peptide 1-76 (N-terminus of the mature
  protein, Ala-77, N-acetylated; mapped by envelope proteomics, PMID:12766230); twelve
  predicted transmembrane helices; CidB/LrgB family (Pfam PF04172, InterPro IPR007300;
  TCDB 2.A.122.2.1).
• Earlier name AtLrgB, from homology to the bacterial LrgA/LrgB holin-like proteins
  PMID:21916894.

Molecular function: glycolate/glycerate transmembrane transport

• Identified by coexpression with photorespiratory genes and reverse genetics
  PMID:23382251.
• Transport evidence (Pick et al. 2013):
• liposome uptake of 14C-glycerate with saturation kinetics, though with high background
  PMID:23382251;
• isolated plgg1-1 chloroplasts cannot drive glycerate-dependent O2 evolution
  PMID:23382251;
• 18O2 flux shows glycolate trapped in the chloroplast PMID:23382251.
• Conclusion PMID:23382251.
• Independent heterologous evidence: PLGG1 rescues a yeast glycolate-uptake mutant
  PMID:28351992. BASS6 shares glycolate export, PLGG1 alone
  imports glycerate PMID:28351992; PLGG1 is described as an antiporter PMID:28351992. GO has no glycolate:glycerate antiporter
  term (OLS search, this review); the two substrate-specific transporter activity terms are
  used.
• Older biochemistry in pea/spinach had already shown a single envelope carrier for both
  substrates PMID:22303256.
• Plasticity: plgg1-1 is not limiting under low light, implying alternative routes
  PMID:27251551.

Biological process: photorespiration

• PMID:23382251 and glycolate/glycerate accumulate PMID:23382251; complementation restores the phenotype
  PMID:23382251.
• Orthologs in rice (OsPLGG1a/b; PMID:33483723, PMID:32038690, not cached) and moss
  (PpLrgB1; PMID:25793376, not cached) were reported with similar photorespiratory
  phenotypes; I only have PubMed abstracts for these and did not cite them in the review.

Location: chloroplast envelope (inner membrane)

• Envelope proteomics (PMID:12766230, PMID:12938931, PMID:20061580) and PLGG1-GFP in
  N. benthamiana protoplasts PMID:23382251.
• Inner-membrane assignment comes from TAIR IDA (PMID:21916894, abstract-only in cache)
  and HDA (PMID:12766230, abstract-only). The abstract of PMID:21916894 only says
  "chloroplast envelope membrane protein". I defer to the curators who read the full text.

Earlier interpretations: chloroplast development / cell death

• The atlrgB mutants show interveinal chlorosis and premature necrosis PMID:21916894 and lesion-mimic-like cell death PMID:22180599; chlorosis was
  suppressed in continuous light PMID:22180599.
• Pick et al. reinterpret these as secondary consequences of photorespiratory metabolite
  toxicity PMID:23382251. UniProt records the same as a CAUTION.
  The GO "chloroplast organization" IMP is therefore treated as an over-annotation of an
  indirect effect.

ABA, stomata, drought, lateral roots (PMID:29097201, abstract only)

• PMID:29097201 and
  PMID:29097201
• PLGG1 is not expressed in roots (PMID:22180599, PMID:21916894), so the root phenotype is
  presumably systemic. No mechanism linking a plastid glycolate/glycerate transporter to
  ABA signalling is given in the abstract. Kept as non-core acts_upstream_of_or_within
  phenotypes; full text not available to me.

Immunity (not reviewed)

• PMID:42222920 (2026, Plant Cell Environ) links plgg1 and hpr1 to bacterial susceptibility,
  largely rescued by elevated CO2. Not cached and not used.