CUT1, an arabidopsis gene required for cuticular wax biosynthesis and pollen fertility, encodes a very-long-chain fatty acid condensing enzyme

Land plants secrete a layer of wax onto their aerial surfaces that is essen tial for survival in a terrestrial environment. This wax is composed of lon g-chain, aliphatic hydrocarbons derived from very-long-chain fatty acids (V LCFAs). Using the Arabidopsis expressed sequence tag database, we have iden tified a gene, designated CUT1, that encodes a VLCFA condensing enzyme requ ired for cuticular wax production. Sense suppression of CUT1 in transgenic Arabidopsis plants results in waxless (eceriferum) stems and siliques as we ll as conditional male sterility. Scanning electron microscopy revealed tha t this was a severe waxless phenotype, because stems of CUT1-suppressed pla nts were completely devoid of wax crystals. Furthermore, chemical analyses of waxless plants demonstrated that the stem wax load was reduced to 6 to 7 % of wild-type levels. This value is lower than that reported for any of th e known eceriferum mutants. The severe waxless phenotype resulted from the downregulation of both the decarbonylation and acyl reduction wax biosynthe tic pathways. This result indicates that CUT1 is involved in the production of VLCFA precursors used for the synthesis of all stem wax components in A rabidopsis. In CUT1-suppressed plants, the C24 chain-length wax components predominate, suggesting that CUT1 is required for elongation of C24 VLCFAs. The unique wax composition of CUT1-suppressed plants together with the fac t that the location of CUT1 on the genetic map did not coincide with any of the known ECERIFERUM loci suggest that we have identified a novel gene inv olved in wax biosynthesis, CUT1 is currently the only known gene with a cle arly established function in wax production.