Biosynthesis and secretion of mugineic acid family phytosiderophores in zinc-deficient barley
Biosynthesis and secretion of mugineic acid family phytosiderophores in zinc-deficient barley
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DOI：
10.1111/j.1365-313x.2006.02853.x
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发表时间：
2006-10-01
期刊：
影响因子：
7.2
通讯作者：
Nishizawa, Naoko K.
中科院分区：
文献类型：
--
作者：
Suzuki, Motofumi;Takahashi, Michiko;Nishizawa, Naoko K.
慕尼酸家族植物铁载体(MAs)是禾本科植物对缺铁反应产生的金属螯合剂，但目前关于缺锌时Mas分泌的证据是相互矛盾的。我们的高效液相分析表明，缺锌诱导大麦植株合成和分泌Mas。缺锌根中参与MAs合成的酶HvNAS1、HvNAAT-A、HvNAAT-B、HvIDS2和HvIDS3的转录本水平升高。利用基因芯片对蛋氨酸循环相关基因的研究表明，在缺锌和缺铁的大麦根中，这些基因的转录都增加了，这可能允许植物满足其对蛋氨酸的需求，蛋氨酸是合成Mas的前体。此外，HvNAAT-B转录本在缺锌植株中检测到，而在缺铁植株中未检测到。缺锌大麦体内MAS合成增加不是由于缺铁所致，而是因为缺锌大麦比对照植株积累了更多的铁，缺锌植株的铁蛋白转录本增加，缺锌促进了铁从根到地的运输。此外，利用正电子发射示踪成像系统(PEIPS)的分析证实，缺锌大麦根部吸收的锌-62(II)-MAs多于锌-62(2+)。这些数据表明，缺锌引起的MA的生物合成和分泌增加并不是由于诱导的缺铁，分泌的MA能有效地吸收土壤中的锌。
Mugineic acid family phytosiderophores (MAs) are metal chelators that are produced in graminaceous plants in response to iron (Fe) deficiency, but current evidence regarding secretion of MAs during zinc (Zn) deficiency is contradictory. Our studies using HPLC analysis showed that Zn deficiency induces the synthesis and secretion of MAs in barley plants. The levels of the HvNAS1, HvNAAT-A, HvNAAT-B, HvIDS2 and HvIDS3 transcripts, which encode the enzymes involved in the synthesis of MAs, were increased in Zn-deficient roots. Studies of the genes involved in the methionine cycle using microarray analysis showed that the transcripts of these genes were increased in both Zn-deficient and Fe-deficient barley roots, probably allowing the plant to meet its demand for methionine, a precursor in the synthesis of MAs. In addition, HvNAAT-B transcripts were detected in Zn-deficient shoots, but not in those that were deficient in Fe. Increased synthesis of MAs in Zn-deficient barley was not due to a deficiency of Fe, because Zn-deficient barley accumulated more Fe than did the control plants, ferritin transcripts were increased in Zn-deficient plants, and Zn deficiency promoted Fe transport from root to shoot. Moreover, analysis using the positron-emitting tracer imaging system (PETIS) confirmed that more Zn-62(II)- MAs than Zn-62(2+) were absorbed by the roots of Zn-deficient barley plants. These data suggest that the increased biosynthesis and secretion of MAs arising from a shortage of Zn are not due to an induced Fe deficiency, and that secreted MAs are effective in absorbing Zn from the soil.