Heat-stress induced synthesis of chloroplast protein synthesis elongation factor (EF-Tu) in a heat-tolerant maize line
Heat-stress induced synthesis of chloroplast protein synthesis elongation factor (EF-Tu) in a heat-tolerant maize line
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DOI：
10.1007/s004250000416
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发表时间：
2001-02-01
期刊：
影响因子：
4.3
通讯作者：
Ristic, Z
中科院分区：
文献类型：
--
作者：
Bhadula, SK;Elthon, TE;Ristic, Z
耐热玉米 (Zea mays L.) 品系 ZPBL 1304 合成了一组独特的 5 种 45 kDa 热休克多肽。先前的研究表明这些多肽可能在玉米耐热性的发展中发挥作用(Ristic等人，1996，J.Plant Physiol.149：424-432；Ristic等人，1998，J.PlantPhysiol.153：497-505)。在本研究中，我们分离了这些多肽，对它们进行了测序，并研究了它们的亚细胞分布和起源。在 45 kDa 的 5 种多肽中，包括两种最丰富的多肽在内的 3 种多肽产生了与叶绿体和细菌蛋白质合成延伸因子 (EF-Tu) 相似的氨基酸序列。使用针对玉米 EF-Tu 的抗体进一步证实了这一点，该抗体与 45-kDa 热休克蛋白表现出非常强烈的反应。对亚细胞分布和起源的研究表明，45-kDa 多肽定位于叶绿体，并且可能源自核。先前从玉米 B73 品系中分离出的全长玉米 EF-Tu cDNA (Zmeftul) 用作探针，对从 ZPBL 1304 玉米品系中提取的 RNA 进行 Northern 印迹分析（Zmeftul 的核苷酸和推导的氨基酸序列与水稻 EF-Tu 序列有 88% 的同一性）。 Northern 印迹显示热应激期间 EF-Tu mRNA 的稳态水平增加了 1.85 倍。热应激期间 EF-Tu 转录物水平的增加伴随着 EF-Tu 蛋白水平的增加。与对照叶绿体相比，从热应激植物中分离的叶绿体也具有更高水平的 EF-Tu。玉米 EF-Tu 多肽显示出与细菌 EF-Tu 有 > 80% 的序列相似性，细菌 EF-Tu 最近已被证明具有分子伴侣的功能，并在保护其他蛋白质免受热变性中发挥作用（Caldas 等人，1998，J. Biol. Chem. 273:11478-11482）。据推测，ZPBL 1304 玉米品系的叶绿体 EF-Tu 在耐热性的发展中发挥重要作用。
A heat-tolerant maize (Zea mays L.) line, ZPBL 1304, synthesizes a unique set of five heat-shock polypeptides of 45 kDa. Previous studies suggested that these polypeptides might play a role in the development of thermotolerance in maize (Ristic et al., 1996, J. Plant Physiol. 149:424-432; Ristic et al., 1998, J. Plant Physiol. 153:497-505). In the present study, we isolated these polypeptides, sequenced them, and investigated their subcellular distribution and origin. Of the five polypeptides of 45 kDa, three polypeptides, including the two most abundant ones, yielded amino acid sequences similar to the chloroplast and bacterial protein synthesis elongation factor (EF-Tu). This was further confirmed using an antibody raised against maize EF-Tu, which showed a very strong reaction with the 45-kDa heat-shock protein(s). Studies on subcellular distribution and origin revealed that the 45-kDa polypeptides were localized to the chloroplasts, and were likely of nuclear origin. A full-length maize EF-Tu cDNA (Zmeftul), previously isolated from the B73 line of maize, was used as a probe for northern blot analysis of RNA extracted from the ZPBL 1304 maize line (the nucleotide and deduced amino acid sequences of Zmeftul are 88% identical to the rice EF-Tu sequence). Northern blots showed a 1.85-fold increase in steady-state levels of EF-Tu mRNA during heat stress. An increase in EF-Tu transcript levels during heat stress was accompanied by increased levels of the EF-Tu protein. Isolated chloroplasts from heat-stressed plants also had higher levels of EF-Tu as compared to control chloroplasts. The maize EF-Tu polypeptides showed > 80% sequence similarity with the bacterial EF-Tu, which has recently been shown to function as a molecular chaperone and to play a role in the protection of other proteins from thermal denaturation (Caldas et al., 1998, J. Biol. Chem. 273:11478-11482). It is hypothesized that chloroplast EF-Tu of the ZPBL 1304 maize line plays an important role in the development of thermotolerance.