Guard cell apoplastic photosynthate accumulation corresponds to a phloem-loading mechanism
Guard cell apoplastic photosynthate accumulation corresponds to a phloem-loading mechanism
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DOI：
10.1093/jxb/erm262
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发表时间：
2007-01-01
影响因子：
6.9
通讯作者：
Riddle, Kimberly A.
中科院分区：
文献类型：
--
作者：
Kang, Yun;Outlaw, William H., Jr.;Riddle, Kimberly A.
质外体韧皮部装载者在将易位的糖（原型为蔗糖）从叶肉移动到伴细胞-筛管元件复合体中具有质外体步骤。在这些植物中，叶质外体蔗糖在光周期期间通过蒸腾作用在保卫细胞壁中浓缩到名义上150 mM。这种浓度的外部蔗糖足以减少气孔孔径大小在一个孤立的系统，并调节某些基因的表达。与质外体韧皮部装载器相反，在另一个极端，严格共质体韧皮部装载器在韧皮部装载中缺乏质外体步骤，并且主要运输棉子糖家族寡糖（RFO），其在叶质外体中处于低浓度。在这里，韧皮部加载机制和相关的现象对保卫细胞的直接环境的影响进行了报道。作为第一步，韧皮部分泌物的碳水化合物分析证实了罗勒（罗勒L。CV.最小）作为共质体韧皮部装载物种。在此基础上，对罗勒的气孔生理进行了研究，以期建立罗勒作为保卫细胞共质体韧皮部负载模式植物。[C-14]通过切割的叶柄饲喂的甘露醇在保卫细胞周围积累，表明连续的叶质外体。叶片质外体中RFO+蔗糖+己糖浓度较低，
Apoplastic phloem loaders have an apoplastic step in the movement of the translocated sugar, prototypically sucrose, from the mesophyll to the companion cell-sieve tube element complex. In these plants, leaf apoplastic sucrose becomes concentrated in the guard cell wall to nominally 150 mM by transpiration during the photoperiod. This concentration of external sucrose is sufficient to diminish stomatal aperture size in an isolated system and to regulate expression of certain genes. In contrast to apoplastic phloem loaders and at the other extreme, strict symplastic phloem loaders lack an apoplastic step in phloem loading and mostly transport raffinose family oligosaccharides (RFOs), which are at low concentrations in the leaf apoplast. Here, the effects of the phloem-loading mechanism and associated phenomena on the immediate environment of guard cells are reported. As a first step, carbohydrate analyses of phloem exudates confirmed basil (Ocimum basilicum L. cv. Minimum) as a symplastic phloem-loading species. Then, aspects of stomatal physiology of basil were characterized to establish this plant as a symplastic phloem-loading model species for guard cell research. [C-14]Mannitol fed via the cut petiole accumulated around guard cells, indicating a continuous leaf apoplast. The (RFO+sucrose+hexoses) concentrations in the leaf apoplast were low,