Loss of the AKT2/3 potassium channel affects sugar loading into the phloem of Arabidopsis
Loss of the AKT2/3 potassium channel affects sugar loading into the phloem of Arabidopsis
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DOI：
10.1007/s00425-002-0895-1
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发表时间：
2002-12-01
期刊：
影响因子：
4.3
通讯作者：
Hedrich, R
中科院分区：
文献类型：
--
作者：
Deeken, R;Geiger, D;Hedrich, R
AKT 2/3家族的成员已被鉴定为光合作用诱导的韧皮部K+通道。在这里，我们描述了从拟南芥（L.）中分离和表征AKT 2/3功能丧失突变体（akt 2/3-1）。嘿显微放射自显影（CO2）-C-14在光下孵育后显示，（CO2）-C-14衍生的光降解产物的主要部分泄漏出筛管似乎不能有效地重新加载（检索）到突变体的韧皮部。使用蚜虫花柱切除技术，我们发现，韧皮部汁液的突变体，缺乏韧皮部通道的AKT 2/3型，只含有一半的蔗糖含量的野生型。此外，akt 2/3突变体表现出降低K+依赖性的韧皮部电位。表达韧皮部蔗糖/质子同向转运体的爪蟾卵母细胞在蔗糖应用后去极化。然而，当韧皮部通道共表达时-模仿筛管/伴细胞复合体中的情况-去极化被阻止。从我们的研究中，我们因此得出结论，AKT 2/3调节蔗糖/H+共转运蛋白通过韧皮部电位。
Members of the AKT2/3 family have been identified as photosynthate-induced phloem K+ channels. Here we describe the isolation and characterisation of an AKT2/3 loss-of-function mutant (akt2/3-1) from Arabidopsis thaliana (L.) Heynh. Micro autoradiography following (CO2)-C-14 incubation in the light revealed that a major fraction of (CO2)-C-14-derived photosynthates leaking out of sieve tubes appears not to be effectively reloaded (retrieval) into the phloem of the mutant. Using the aphid stylectomy technique we showed that the phloem sap of the mutant, lacking the phloem channels of the AKT2/3 type, contained only half the sucrose content of the wild type. Furthermore, the akt2/3 mutant exhibited a reduced K+ dependence of the phloem potential. Xenopus oocytes expressing the phloem sucrose/proton symporter depolarise upon sucrose application. When, however, the phloem channel was co-expressed - mimicking the situation in the sieve tube/companion cell complex - depolarisation was prevented. From our studies we thus conclude that AKT2/3 regulates the sucrose/H+ symporters via the phloem potential.