Sugar accumulation and activities of enzymes involved in fructan dynamics from seedling to bulb formation in onion (Allium cepa L.)
Sugar accumulation and activities of enzymes involved in fructan dynamics from seedling to bulb formation in onion (Allium cepa L.)
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DOI：
10.1016/j.scienta.2018.12.013
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发表时间：
2019-03-15
影响因子：
4.3
通讯作者：
Shimura, Hanako
中科院分区：
文献类型：
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作者：
Oku, Satoshi;Ueno, Keiji;Shimura, Hanako
洋葱（Allium cepa L.）在鳞茎中产生以果糖为基础的低聚糖（果聚糖）作为主要的储备碳水化合物。我们以前发现收获的鳞茎中果聚糖量的品种差异;“北桃2000”积累了高水平的果聚糖，具有高聚合度，而“极星星”有低的量，积累主要是单糖和蔗糖。在这项研究中，我们研究了果聚糖的积累和酶的活性参与果聚糖代谢途径中更详细地在地上和地下组织收获整个洋葱发展。果聚糖水平在两个品种的分析表明，果聚糖积累水平几乎相同，在地上和基生叶鳞茎形成前，但果聚糖水平差异显着，在鳞茎形成后的后期，在收获的鳞茎果聚糖含量的品种差异是明显的，只有在收获前2或3周。在早期发育阶段，“极星星”中的果聚糖水平与“北见寺2000”中的果聚糖水平相当，表明“极星星”可以合成高度聚合的果聚糖。在酶活性分析中，'Pole星星'与'Kita-momiji 2000'相比，在鳞茎形成后具有较高的合成果聚糖的活性，并且在鳞茎形成前具有更大的降解蔗糖和果聚糖的潜力，导致地上叶和基生叶中的蔗糖积累较少。这些结果表明，高活性的果聚糖降解酶在'极星星'导致较少的果聚糖积累的鳞茎比'北桃寺2000'，因为该品种不能维持高水平的蔗糖，起始底物果聚糖合成。
Onion (Allium cepa L.) produces a fructose-based oligosaccharide (fructan) in the bulb as the major reserve carbohydrate. We previously found varietal differences in fructan quantity in the harvested bulbs; 'Kita-momiji 2000' accumulated a high level of fructans with a high degree of polymerization, while 'Pole Star' had low amounts and accumulated mainly monosaccharides and sucrose. In this study, we examined fructan accumulation and enzymatic activities involved in the fructan metabolic pathway in more detail in both aerial and subterranean tissues that were harvested throughout onion development. Analyses of fructan levels in the two cultivars revealed that levels in fructan accumulation were almost the same in aerial and basal leaves before bulb formation, but fructan levels differed significantly in the late stage after bulb formation; varietal differences in fructan content in the harvested bulb were apparent only during the 2 or 3 weeks before harvest. At an early developmental stage, fructan levels in 'Pole Star' were equivalent to those in 'Kita-momiji 2000', indicating that 'Pole Star' can synthesize highly polymerized fructans. In analyses of enzymatic activities, 'Pole Star' had high activity for synthesizing fructan after bulb formation compared to 'Kita-momiji 2000' and also greater potential for degrading sucrose and fructan before bulb formation, leading to less sucrose accumulation both in aerial and basal leaves. These results suggest that high activities for fructan degradation enzymes in 'Pole Star' cause less fructan accumulation in the bulb than in 'Kita-Momiji 2000' because this cultivar cannot sustain high levels of sucrose, the starting substrate for fructan synthesis.