【摘 要】
：
In contrast to the detailed molecular knowledge available on anthocyanin synthesis,little is known for the catabolism pathway of anthocyanins in plants.Litchi(Litchi chinensis Sonn.)fruit lose their a
【机 构】
：
College of Life Sciences,South China Agricultural University,Guangzhou 510642,China
【出 处】
：
2015 International Conference on Fruit Quality Biology (第二届果
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In contrast to the detailed molecular knowledge available on anthocyanin synthesis,little is known for the catabolism pathway of anthocyanins in plants.Litchi(Litchi chinensis Sonn.)fruit lose their attractive red color soon after harvest.The mechanism that leads to the quick anthocyanin degradation in pericarp is still not well understood.Using partially purified anthocyanins from Litchi pericarp as a substrate,an anthocyanin degradation enzyme(ADE)was purified to homogeneity by sequential column chromatography.The purified ADE was of 116 kD by SDS-PAGE,and was identified as a laccase(ADE/LAC).The full length cDNA encoding ADE/LAC was obtained and a polyclonal antibody raised against a deduced peptide of the gene recognized the ADE protein.ADE/LAC gene expressed higher levels in the pericarp than other tissues,and around 1000folds higher than a PPO(Polyphenol oxidase)gene in the pericarp.Epicatechin appeared to be the most favorite substrate for the enzyme.ADE/LAC anthocyanin degradation was dependent on the presence of epicatechin,suggesting an ADE/LAC epicatechin coupled oxidation model.This model was supported by dramatic decrease in epicatechin content in pericarp with anthocyanin degradation.Immune-gold labeling observation by transmission electron microscopy suggests that ADE/LAC colocalizes with phenol substances in the vacuole and cytoplasm.However,after pericarp browning ADE/LAC was also secreted to the cell wall and intercellular space.ADE/LAC vacuolar localization,high expression levels in pericarp,and high epicatechin dependent anthocyanin degradation support its central role in the pigment breakdown during pericarp browning.
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