Cação S M B, Leite T F, Budzinski I G F, dos Santos T B, Scholz M B S, Carpentieri-Pipolo V, Domingues D S, Vieira L G E, Pereira L F P
Laboratório de Biotecnologia Vegetal, Instituto Agronômico do Paraná, Londrina, PR, Brasil.
Genet Mol Res. 2012 Sep 3;11(3):3186-97. doi: 10.4238/2012.September.3.7.
Coffee quality is directly related to the harvest and post harvest conditions. Non-uniform maturation of coffee fruits, combined with inadequate harvest, negatively affects the final quality of the product. Pectin methylesterase (PME) plays an important role in fruit softening due to the hydrolysis of methylester groups in cell wall pectins. In order to characterize the changes occurring during coffee fruit maturation, the enzymatic activity of PME was measured during different stages of fruit ripening. PME activity progressively increased from the beginning of the ripening process to the cherry fruit stage. In silico analysis of expressed sequence tags of the Brazilian Coffee Genome Project database identified 5 isoforms of PME. We isolated and cloned a cDNA homolog of PME for further characterization. CaPME4 transcription was analyzed in pericarp, perisperm, and endosperm tissues during fruit development and ripening as well as in other plant tissues. Northern blot analysis revealed increased transcription of CaPME4 in the pericarp 300 days after flowering. Low levels of CaPME4 mRNAs were observed in the endosperm 270 days after flowering. Expression of CaPME4 transcripts was strong in the branches and lower in root and flower tissues. We showed that CaPME4 acts specifically during the later stages of fruit ripening and possibly contributes to the softening of coffee fruit, thus playing a significant role in pectin degradation in the fruit pericarp.
咖啡品质与收获及收获后的条件直接相关。咖啡果实成熟不均匀，再加上收获不当，会对产品的最终品质产生负面影响。果胶甲酯酶（PME）由于能水解细胞壁果胶中的甲酯基团，在果实软化过程中发挥着重要作用。为了表征咖啡果实成熟过程中发生的变化，在果实成熟的不同阶段测定了PME的酶活性。从成熟过程开始到樱桃果阶段，PME活性逐渐增加。对巴西咖啡基因组计划数据库的表达序列标签进行电子分析，鉴定出5种PME同工型。我们分离并克隆了PME的一个cDNA同源物，以进行进一步表征。在果实发育和成熟过程中以及在其他植物组织中，分析了CaPME4在果皮、外胚乳和胚乳组织中的转录情况。Northern印迹分析显示，开花后300天，CaPME4在果皮中的转录增加。开花后270天，在胚乳中观察到低水平的CaPME4 mRNA。CaPME4转录本在枝条中表达强烈，在根和花组织中表达较低。我们表明，CaPME4在果实成熟后期特异性起作用，可能有助于咖啡果实软化，从而在果实果皮的果胶降解中发挥重要作用。
