Suzuki Motofumi, Takahashi Michiko, Tsukamoto Takashi, Watanabe Satoshi, Matsuhashi Shinpei, Yazaki Junshi, Kishimoto Naoki, Kikuchi Shoshi, Nakanishi Hiromi, Mori Satoshi, Nishizawa Naoko K
Department of Global Agricultural Sciences, Graduate School of Agricultural and Life Science, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan.
Plant J. 2006 Oct;48(1):85-97. doi: 10.1111/j.1365-313X.2006.02853.x.
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 62Zn(II)-MAs than 62Zn2+ 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.
mugineic酸家族植物铁载体（MAs）是禾本科植物在缺铁时产生的金属螯合剂，但目前关于缺锌时MAs分泌的证据相互矛盾。我们使用高效液相色谱分析的研究表明，缺锌会诱导大麦植株中MAs的合成与分泌。编码参与MAs合成的酶的HvNAS1、HvNAAT-A、HvNAAT-B、HvIDS2和HvIDS3转录本水平在缺锌根中增加。使用微阵列分析对参与蛋氨酸循环的基因进行的研究表明，这些基因的转录本在缺锌和缺铁的大麦根中均增加，这可能使植物能够满足其对蛋氨酸的需求，蛋氨酸是MAs合成的前体。此外，在缺锌的地上部分检测到HvNAAT-B转录本，但在缺铁的地上部分未检测到。缺锌大麦中MAs合成增加并非由于缺铁，因为缺锌大麦比对照植株积累了更多的铁，缺锌植株中铁蛋白转录本增加，且缺锌促进了铁从根向地上部分的运输。此外，使用正电子发射示踪成像系统（PETIS）进行的分析证实，缺锌大麦植株的根吸收的62Zn（II）-MAs比62Zn2+更多。这些数据表明，锌短缺引起的MAs生物合成和分泌增加并非由于诱导缺铁所致，且分泌的MAs在从土壤中吸收锌方面是有效的。
