IRX10L notes (IRX10 family review, 2026-10-29)

Deep research

just deep-research-falcon ARATH IRX10L --fallback perplexity-lite failed in this
session (no provider available: "Provider 'perplexity' not available"). The review
rests on the cached primary literature listed below, read directly.

The IRX10 clade (GT47)

Arabidopsis has two members, IRX10 (At1g27440, Q9FZJ1) and IRX10-L (At5g61840,
Q940Q8), in the exostosin-related GT47 family PTHR11062. PANTHER puts them in
different subfamilies: IRX10 in SF370 ("BETA-1,4-XYLOSYLTRANSFERASE IRX10-RELATED")
and IRX10L in SF200 ("BETA-1,4-XYLOSYLTRANSFERASE IRX10L-RELATED"), which in the
local PTHR11062 entries table also holds rice Os01g0926700 (Q8S1X7) and moss
GT47A (A9RGD8). Both are xylan backbone beta-1,4-xylosyltransferases (xylan
synthases).

• Biochemistry: purified IRX10-L polymerises beta-1,4-xylan from UDP-Xyl
  PMID:25141999. AtIRX10 is
  active but weak in vitro PMID:25139408.
• Genetics: redundant pair PMID:18980662. IRX10 is the major
  secondary-wall gene PMID:20424005, IRX10L the primary-wall gene
  PMID:26043357.
• Complex: in asparagus, IRX9, IRX10 and IRX14A are all needed for activity in
  planta and form a Golgi complex PMID:26951434.

IRX10L-specific

• Purified catalytic domain polymerises xylan unaided; renamed XYLAN SYNTHASE-1
  PMID:25141999.
• Main primary-wall gene: irx10L callus loses the GUX3-decorated primary-wall xylan
  and most microsomal xylosyltransferase activity PMID:26043357.
• Minor in secondary walls: no phenotype alone, essential only without IRX10
  PMID:18980662.
• Two rows citing PMID:25141999 (IMP cell wall biogenesis, IDA Golgi) are recorded as
  TAIR evidence-code defects; that paper is in vitro only.
• PANTHER SF200, together with rice IRX10, moss GT47A and Klebsormidium KfXYS1.

Curation issues found (shared with the paralog)

1. GO:0080116 glucuronoxylan glucuronosyltransferase activity (IMP, PMID:18980662,
   on both genes; IBA on IRX10L from PTN001667002) is the wrong MF. The paper
   reports loss of beta(1,4) xylosyltransferase activity. GlcA transfer is done by
   GT8 GUX enzymes PMID:26043357. MODIFY to GO:0047517;
   recorded as a TAIR source defect. The term probably stems from the GUT1/GUT2
   aliases (after tobacco NpGUT1).
2. GO:0009101 glycoprotein biosynthetic process (InterPro2GO, IPR004263) does not
   apply to plant xylan synthases; removed.
3. IRX10L rows citing PMID:25141999 as IMP (cell wall biogenesis) and IDA (Golgi
   apparatus): the paper is in vitro biochemistry only and cites Sogaard et al.
   2012 for topology. Terms kept/refined, evidence-code defects recorded.
4. UniProt naming (now recorded as UNIPROT source_defects on the GO:0080116 IMP row): both Q9FZJ1 and Q940Q8 carry the alt names "Glucuronoxylan
   glucuronosyltransferase 1/2" (AtGUT1/AtGUT2), and the IRX10 FUNCTION text says
   "especially in the formation of GlcUA side chain of xylans". Both are legacy and
   conflict with the direct biochemistry. Worth reporting to UniProt.
5. Topology: UniProt models residues 1-21/2-22 as a type II signal anchor, while
   Wu et al. 2009 and Urbanowicz et al. 2014 describe a signal peptide; AoIRX10 is
   described as lumenal and held by IRX9/IRX14. Golgi membrane kept as the
   location; the anchoring mechanism is left as a question.