75 Integrating Membrane Transport with Male Gametophyte ... - TAIR

329 Composition of Esters in the Stem Wax of Arabidopsis cer Mutants
Christine Lai, Ljerka Kunst, Xuemin Wu, Stephen Greer, Reinhard Jetter
University of British Columbia, Dept. of Botany
Primary plant surfaces are covered by a cuticle consisting of very long chain ‘waxes’ embedded in and deposited
on a fatty acid polyester matrix of ‘cutin’. The cuticle serves as a crucial first line of defense against biotic and abiotic
stress from the plant’s environment. A number of Arabidopsis mutants have been identified that are deficient in cuticle
formation and provide important tools for studying the biosynthesis and export of cuticular wax components. Although
the wax of these cer mutants has been analyzed in some detail, data on the chain length and isomer composition of the
alkyl esters are missing to date.
Wax alkyl esters are composed of straight chain, saturated fatty acids bonded to very long chain alcohols. Are the
esterified acids and alcohols the same as those found as free compounds in the wax mixture
For the current study, cer mutants with known altered composition of free wax alcohols were selected and their
ester composition was determined by GC-FID and GC-MS. Wax esters constituted 0.2 - 0.6 µg/cm² of the mutant wax
mixtures. Palmitate was the predominant ester acid, while C22 to C30 alcohols were found esterified. The chain length
patterns of free and esterified alcohols matched for all those mutants with alcohol/ester amounts higher than corresponding
wildtypes. In contrast, both patterns differed for other mutants with alcohol quantities below the wildtype level. The
biosynthetic relevance of these findings will be discussed.
330 Assessment of tocopherol recycling during light stress in Arabidopsis thaliana
Naoko Kobayashi, Dean DellaPenna
Michigan State University
Tocopherols (Vitamin E) are lipid-soluble antioxidants synthesized by all plants and cyanobacteria. Genes encoding
the main tocopherol biosynthetic pathway have now been isolated primarily from mutant analyses in Arabidopsis thaliana,
and used to successfully engineer the content of tocopherols and biosynthetic intermediates in plants. Tocopherols play an
important role as antioxidants which results in the generation of various tocopherol oxidation products. In animal systems
α-tocopherol quenches and scavenges lipid peroxy radicals and can be reversibly oxidized in a redox cycle or oxidized
further to products such as α-tocopherolquione (TQ), epoxy-α-tocopherolquiones, and α-tocopherolhydroquionone (THQ).
Unlike animals, plants can synthesize tocopherols and it is therefore possible that tocopherols might be regenerated from
oxidation products by dehydrating the 3`position of the phytyl tail of TQ and THQ and then cyclizing the products to
reform a chromanol ring. To test whether such a system is operating in plants, we have fed isolated Arabidopsis chloroplasts
labeled tocopherol oxidation products and followed the production of any newly formed compounds. The effects of
different light intensity (100μmol and 1,300μmol), cofactors (NADPH, ATP and GSH) and different concentration of
detergent (deriphat) will be presented.