韧皮部
质外体
转化酶
蔗糖
生物
胞间连丝
猕猴桃
蔗糖合成酶
薄壁组织
生物化学
蔗糖磷酸合酶
筛管元件
猕猴桃
细胞壁
植物
作者
Cheng Chen,Y. Yuan,Chen Zhang,Huixia Li,Fengwang Ma,Mingjun Li
出处
期刊:Plant Science
[Elsevier]
日期:2017-02-01
卷期号:255: 40-50
被引量:42
标识
DOI:10.1016/j.plantsci.2016.11.011
摘要
Phloem unloading plays a pivotal role in photoassimilate partitioning and the accumulation of sugars in sink organs, e.g. fruit. Here, we investigated the pathway of sucrose unloading in kiwifruit (Actinidia deliciasa cv. Qinmei) using a combination of electron microscopy, transport of the phloem-mobile symplastic tracer carboxyfluorescein and enzyme activity and gene expression assays. Our structural investigation revealed that the sieve element-companion cell complex of bundles feeding the fruit flesh was symplastically isolated from its surrounding parenchyma cells throughout fruit development, whereas numerous plasmodesmata were present between the phloem parenchyma cells. Consistent with this, carboxyfluorescein unloading showed that the dye remained confined in the phloem strands during fruit development. The activities and expression of cell wall acid invertase in fruit flesh were lower than those of other enzymes that catalyze sucrose dissociation. However, sucrose synthase showed higher enzyme activities and mRNA expression in fruit flesh compared with other detected enzymes. These results imply that, in kiwifruit flesh, phloem unloading of sucrose is predominantly an apoplastic pathway during fruit development, and that sucrose synthase is a key enzyme for sucrose post-unloading pathways.
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