Sulfur Transfer through an Arbuscular Mycorrhiza
Sulfur Transfer through an Arbuscular Mycorrhiza
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DOI：
10.1104/pp.108.129866
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发表时间：
2009-01-01
期刊：
影响因子：
7.4
通讯作者：
Shachar-Hill, Yair
中科院分区：
文献类型：
--
作者：
Allen, James W.;Shachar-Hill, Yair
尽管硫（S）对于植物营养很重要，但丛枝菌根（AM）共生在硫吸收中的作用却很少受到关注。为了解决这个问题，对转化胡萝卜（Daucus carota）根的菌根和在双室培养皿上单细胞生长的根内球囊霉进行了 S-35 标记实验。当改变根部可用的硫酸盐浓度并向真菌室提供半胱氨酸 (Cys)、蛋氨酸 (Met) 或谷胱甘肽时，分析了真菌对 (SO42-)-S-35 的吸收和转移以及由此产生的 S-35 分配到宿主根部不同代谢池中的情况。此外，还测定了 S-35 从还原 S 源 [S-35] Cys 和 [S-35] Met 中的摄取、转移和分配。硫酸盐被真菌吸收并转移到菌根根，在中等（不限制生长）浓度的硫酸盐下，根部的硫含量增加了 25%。菌根根室中的高硫酸盐水平使真菌室对 (SO42-)-S-35 的吸收减半。在 1 个月内，向真菌室中添加 1 mM Met、Cys 或谷胱甘肽可分别减少硫酸盐的转移 26%、45% 和 80%。无论真菌室中提供的是 (SO42-)-S-35、[S-35] Cys 或 [S-35] Met，相似数量的 S-35 都会转移到菌根根。鉴定了假定的 S 同化基因的真菌转录本，表明反式硫化途径的存在。在 Cys 存在的情况下，真菌硫酸盐转移的抑制与推定的硫酸盐通透酶而不是硫酸盐腺苷酸转移酶转录物的减少同时发生，这表明真菌转录调节在 S 转移到宿主中的作用。提出了可测试模型来描述通过 AM 共生获取根 S。
Despite the importance of sulfur (S) for plant nutrition, the role of the arbuscular mycorrhizal (AM) symbiosis in S uptake has received little attention. To address this issue, S-35-labeling experiments were performed on mycorrhizas of transformed carrot (Daucus carota) roots and Glomus intraradices grown monoxenically on bicompartmental petri dishes. The uptake and transfer of (SO42-)-S-35 by the fungus and resulting S-35 partitioning into different metabolic pools in the host roots was analyzed when altering the sulfate concentration available to roots and supplying the fungal compartment with cysteine (Cys), methionine (Met), or glutathione. Additionally, the uptake, transfer, and partitioning of S-35 from the reduced S sources [S-35] Cys and [S-35] Met was determined. Sulfate was taken up by the fungus and transferred to mycorrhizal roots, increasing root S contents by 25% in a moderate (not growth-limiting) concentration of sulfate. High sulfate levels in the mycorrhizal root compartment halved the uptake of (SO42-)-S-35 from the fungal compartment. The addition of 1 mM Met, Cys, or glutathione to the fungal compartment reduced the transfer of sulfate by 26%, 45%, and 80%, respectively, over 1 month. Similar quantities of S-35 were transferred to mycorrhizal roots whether (SO42-)-S-35, [S-35] Cys, or [S-35] Met was supplied in the fungal compartment. Fungal transcripts for putative S assimilatory genes were identified, indicating the presence of the trans-sulfuration pathway. The suppression of fungal sulfate transfer in the presence of Cys coincided with a reduction in putative sulfate permease and not sulfate adenylyltransferase transcripts, suggesting a role for fungal transcriptional regulation in S transfer to the host. Atestable model is proposed describing root S acquisition through the AM symbiosis.