LEAF EPICUTICULAR WAXES OF THE ECERIFERUM MUTANTS IN ARABIDOPSIS

Wild-type Arabidopsis leaf epicuticular wax (EW) occurs as a smooth la yer over the epidermal surface, whereas stem EW has a crystalline micr ostructure. Wild-type EW load was more than 10-fold lower on leaves th an on stems. Compared with the EW on wild-type stems, EW on wild-type leaves had a much higher proportion of their total EW load in the form of alkanes and 1-alcohols; a large reduction in secondary alcohols, k etones, and esters; and a chain-length distribution far major EW class es that was skewed toward longer lengths. The eceriferum (cer) mutatio ns often differentially affected leaf and stem EW chemical composition s. For example, the cer2 mutant EW phenotype was expressed on the stem but not on the leaf. Compared to wild type, the amount of primary alc ohols on cer9 mutants was reduced on leaves but elevated on stems, whe reas an opposite differential effect for primary alcohols was observed on cer16 leaves and stems. Putative functions for CER gene products a re discussed. The CER4 and CERC6 gene products may be involved in fatt y aldehyde reduction and C-26 fatty acylcoenzyme A elongation, respect ively. CER1, CER8, CER9, and CER16 gene products may be involved in EW substrate transfer. The CER3 gene product may be involved in release of fatty acids from elongase complexes. CER2 gene product may have reg ulatory functions.