CUT1 (CER6/KCS6; At1g68530; Q9XF43) review notes

Identity and function

CUT1 = CER6 = KCS6, a FAE1-type 3-ketoacyl-CoA synthase (condensing enzyme) of the ER VLCFA elongase PMID:11041893.
Required for wax production; suppression gives waxless stems with wax at 6-7% of WT and conditional male sterility PMID:10330468.
Chain length: C24 components accumulate in suppressed plants PMID:10330468; in yeast KCS6 elongates C22 to C24-C28 PMID:36798704.
Major condensing enzyme for stem wax and pollen coat lipids PMID:12177469.
Expression: epidermis, tapetum; light required, ABA/osmotic stress enhance PMID:12177469.
Localization: ER PMID:36798704.
Falcon deep research (file:ARATH/CUT1/CUT1-deep-research-falcon.md) agrees; notes CER2/CER26 accessory proteins extend elongation beyond C28.

GO:0009922 "fatty acid elongase activity" is now defined as the condensation step (very-long-chain acyl-CoA + malonyl-CoA -> 3-oxoacyl-CoA), i.e. exactly the KCS reaction (checked in local go.db).

ACCEPT: MF (EXP/IBA/IEA), ER/ER membrane (all), VLCFA metabolic (IBA, IDA), wax biosynthesis (IMP), general IEA parents.
KEEP_AS_NON_CORE: response to cold (x2 IEP), response to light (IEP), unidimensional cell growth (IMP; indirect via VLCFA/ethylene, PMID:17993622), cutin-based cuticle development.
MARK_AS_OVER_ANNOTATED: cytoplasm (ISM), mitochondrion (HDA, PMID:28887381 high-throughput co-fractionation).
No NEW terms. Core function uses GO:0042761 and GO:0009923 (validator warns they are not in GOA; kept as they are accurate).
Note: UniProt says CER6 is down-regulated by low temperature (PMID:18465198), whereas PMID:41718707 reports cold induction of KCSs (unnamed in abstract); both kept as non-core IEP.