Time course analysis of gene expression over 24 hours in Fe-deficient barley roots
Time course analysis of gene expression over 24 hours in Fe-deficient barley roots
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DOI：
10.1007/s11103-008-9443-0
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发表时间：
2009-03-01
影响因子：
5.1
通讯作者：
Nishizawa, Naoko K.
中科院分区：
文献类型：
--
作者：
Nagasaka, Seiji;Takahashi, Michiko;Nishizawa, Naoko K.
典型的禾本科植物，大麦分泌麦红酸家族植物铁载体（MA），以获得铁（Fe）。在缺铁条件下，大麦根系分泌MAs显著增加。分泌呈昼夜模式，在日出后2-3 h出现明显高峰，并在几小时内停止。利用基因芯片技术分析了缺铁胁迫下大麦根中的相关基因及其表达的日变化。基因编码的酶参与MAs的生物合成，蛋氨酸循环，蛋氨酸生物合成的铁缺乏高度诱导。硫酸盐转运蛋白的表达也被铁缺乏上调。因此，所有参与从硫吸收和同化的MAs的生物合成途径的基因在缺铁大麦根上调。与MAs分泌相反，这些基因的转录水平没有表现出昼夜变化。内源性MAs的量在MAs分泌停止后的一天内逐渐增加，并在分泌开始前达到最高。这些结果表明，MAs的生物合成，包括供应的底物甲硫氨酸，发生在整个一天，和生物合成的MAs可能积累在大麦根，直到它们分泌到根际。与此相反，铁（III）-MAs复合转运蛋白，两个假定的金属-MAs复合转运蛋白，和HvYS 1的转录水平也增加了铁缺乏大麦根，这些转录水平的两个表现出昼夜节律。Fe（III）-MAs复合转运蛋白可能昼夜吸收Fe（III）-MAs，与MAs的昼夜分泌同步。
Typical for a graminaceous plant, barley secretes mugineic acid-family phytosiderophores (MAs) to acquire iron (Fe). Under Fe-deficient conditions, MAs secretion from barley roots increases markedly. Secretion shows a diurnal pattern, with a clear peak 2-3 h after sunrise and cessation within a few hours. Microarray analyses were performed to profile the Fe deficiency-inducible genes in barley roots and diurnal changes in the expression of these genes. Genes encoding enzymes involved in MAs biosynthesis, the methionine cycle, and methionine biosynthesis were highly induced by Fe deficiency. The expression of sulfate transporters was also upregulated by Fe deficiency. Therefore, all of the genes participating in the MAs pathway from sulfur uptake and assimilation to the biosynthesis of MAs were upregulated in Fe-deficient barley roots. In contrast to MAs secretion, the transcript levels of these genes did not show diurnal changes. The amount of endogenous MAs gradually increased during the day after MAs secretion ceased, and was highest before secretion began. These results show that MAs biosynthesis, including the supply of the substrate methionine, occurs throughout the day, and biosynthesized MAs likely accumulate in barley roots until their secretion into the rhizosphere. In contrast, the levels of transcripts encoding an Fe(III)-MAs complex transporter, two putative metal-MAs complex transporters, and HvYS1 were also increased in Fe-deficient barley roots, and the levels of two of these transcripts showed diurnal rhythms. The Fe(III)-MAs complex transporters may absorb Fe(III)-MAs diurnally, synchronous with the diurnal secretion of MAs.