Li Xingjun, Nakagawa Naoki, Nevins Donald J, Sakurai Naoki
Faculty of Integrated Arts and Sciences, Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-8521, Japan.
Plant Physiol Biochem. 2006 Feb-Mar;44(2-3):115-24. doi: 10.1016/j.plaphy.2006.03.005. Epub 2006 Apr 19.
Changes in pectin, hemicelluloses and cellulose in the cell walls of outer pericarp tissues of kiwifruit (Actinidia deliciosa cv. Hayward) were determined during development. An extensive amylase digestion was employed to remove possible contaminating starch before and after fractionation of wall polysaccharides. An initial treatment of crude cell walls with alpha-amylase and iso-amylase or DMSO, was found to be insufficient removing the contaminating starch from wall polysaccharides. After EDTA and alkaline extraction, the pectic and hemicellulose fractions were again treated with the combination of alpha-amylase and iso-amylase. The amounts of predominant pectic sugars Gal, Rha and Ara, unaffected by the first and second amylase digestion, decreased markedly during the early fruit enlargement (8-12 weeks after anthesis, WAA), then increased during 16-20 WAA, and finally declined during fruit maturity (20-25 WAA). The molecular-mass of pectic polysaccharides decreased during fruit enlargement (8-16 WAA), and then changed little during fruit maturity. The higher molecular-mass components of hemicelluloses in HC-I and HC-II fractions detected at the early stage of fruit enlargement (8-12 WAA) were degraded at the late stage of fruit enlargement (16 WAA), but then remained stable at the much lower molecular-mass till fruit maturity. The amount of Xyl in the HC-II fraction decreased during the early fruit enlargement and fruit maturity, an observation that was consistent with xyloglucan (XG) content. The gel permeation profiles of XG showed a slight increase in higher molecular-mass components during 8-12 WAA, but thereafter there was no significant down-shift of molecular-mass until harvest time. The cellulose fraction increased steadily during fruit enlargement through maturity, but the XG contents in HC-I and HC-II fractions remained at a low level during these stages. Methylation analysis of HC-I and HC-II fractions confirmed the low level of XG in the hemicellulosic fractions. It was suggested that pectin in the outer pericarp of kiwifruit was degraded at the early stage of fruit enlargement, but XG remains constant during fruit enlargement and maturation.
在猕猴桃（美味猕猴桃品种海沃德）发育过程中，测定了其外果皮组织细胞壁中果胶、半纤维素和纤维素的变化。在对细胞壁多糖进行分级分离前后，采用广泛的淀粉酶消化法去除可能存在的淀粉污染物。发现用α-淀粉酶和异淀粉酶或二甲基亚砜对粗细胞壁进行初步处理，不足以从细胞壁多糖中去除淀粉污染物。经乙二胺四乙酸（EDTA）和碱性提取后，果胶和半纤维素组分再次用α-淀粉酶和异淀粉酶联合处理。主要果胶糖半乳糖（Gal）、鼠李糖（Rha）和阿拉伯糖（Ara）的含量，在第一次和第二次淀粉酶消化后未受影响，但在果实早期膨大期（开花后8 - 12周，WAA）显著下降，然后在16 - 20 WAA期间增加，最后在果实成熟期（20 - 25 WAA）下降。果胶多糖的分子量在果实膨大期（8 - 16 WAA）降低，然后在果实成熟期变化不大。在果实膨大早期（8 - 12 WAA）检测到的HC - I和HC - II组分中半纤维素的高分子量成分，在果实膨大后期（16 WAA）被降解，但随后在低得多的分子量下保持稳定直至果实成熟。HC - II组分中木糖（Xyl）的含量在果实早期膨大期和成熟期下降，这一观察结果与木葡聚糖（XG）含量一致。XG的凝胶渗透图谱显示，在8 - 12 WAA期间高分子量成分略有增加，但此后直到收获时分子量没有明显下降。纤维素组分在果实从膨大到成熟的过程中稳步增加，但在这些阶段HC - I和HC - II组分中的XG含量保持在较低水平。对HC - I和HC - II组分的甲基化分析证实了半纤维素组分中XG的低水平。研究表明，猕猴桃外果皮中的果胶在果实膨大早期被降解，但XG在果实膨大期和成熟期保持恒定。
