Cell wall modification is integral to many plant developmental processes where cells need to separate, such as abscission. However, changes in the cell wall composition during natural fruit abscission are poorly understood. In olive (Olea europaea L), some cultivars such as 'Picual' undergo massive natural fruit abscission after fruit ripening. This study investigates the differences in cell wall polysaccharide composition and the localization of pectins and arabinogalactan protein (AGP) in the abscission zone (AZ) during cell separation in order to understand fruit abscission control in 'Picual' olive. To this end, immunogold labeling employing a suite of monoclonal antibodies to cell wall components (JIM13, LM5, LM6, LM19 and LM20) were investigated in olive fruit AZ. Cell wall polysaccharide extraction revealed that the AZ cell separation is related to the de-esterification and degradation of pectic polysaccharides. Moreover, ultrastructural localization showed that both esterified and unesterified homogalacturonans localize mainly in the AZ cell walls, including the middle lamella and tricellular junction zones. Our results indicate that unesterified homogalacturonans are likely to contribute to cell separation in the olive-fruit AZ. Likewise, immunogold labeling demonstrated a decrease of both galactose-rich and arabinose-rich pectins in AZ cell walls during ripe-fruit abscission. In addition, AGPs were localized in the cell wall, plasma membrane, and cytoplasm of AZ cells with lower levels of AGPs during ripe-fruit abscission. This detailed temporal profile of the cell wall polysaccharide composition, and the pectins and AGP immunolocalization in the olive-fruit AZ offers new insights into cell wall remodeling during ripe-fruit abscission.

中文翻译：

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油橄榄果脱落期间果胶和阿拉伯半乳聚糖蛋白的细胞壁组成和超微结构免疫定位。

细胞壁修饰是许多植物需要分离的植物发育过程必不可少的部分，例如脱落。然而，人们对天然水果脱落期间细胞壁组成的变化了解甚少。在橄榄（Olea europaea L）中，某些品种（例如'Picual'）在果实成熟后会经历大量的天然果实脱落。本研究调查了细胞分离过程中细胞壁多糖组成以及果胶和阿拉伯半乳聚糖蛋白（AGP）在脱落区（AZ）中的定位差异，以了解'Picual'橄榄中果实的脱落控制。为此，在橄榄果AZ中研究了针对细胞壁成分（JIM13，LM5，LM6，LM19和LM20）使用一系列单克隆抗体的免疫金标记方法。细胞壁多糖提取表明，AZ细胞分离与果胶多糖的去酯化和降解有关。此外，超微结构定位表明酯化和未酯化的同半乳糖醛酸都主要定位在AZ细胞壁上，包括中间层和三细胞连接区。我们的结果表明，未酯化的高半乳糖醛酸可能有助于橄榄果AZ中的细胞分离。同样，免疫金标记表明成熟果实脱落期间AZ细胞壁中富含半乳糖的果胶和富含阿拉伯糖的果胶均减少。此外，在成熟果实脱落期间，AGP定位于AZ细胞水平较低的AZ细胞的细胞壁，质膜和细胞质中。细胞壁多糖成分的详细时间分布