A PII-like protein in Arabidopsis:: Putative role in nitrogen sensing
A PII-like protein in Arabidopsis:: Putative role in nitrogen sensing
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DOI：
10.1073/pnas.95.23.13965
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发表时间：
1998-11-10
影响因子：
11.1
通讯作者：
Coruzzi, G
中科院分区：
文献类型：
--
作者：
Hsieh, MH;Lam, HM;Coruzzi, G
PII是大肠杆菌和其他细菌中的一种蛋白质变构效应因子，它在转录和翻译后水平间接调节谷氨酰胺合成酶，以响应氮素的供应。支持植物有氮调控系统的数据(S)包括先前的研究，表明植物氮同化基因如谷氨酰胺合成酶(Gln)和天冬酰胺合成酶(Asn)的基因水平受碳和有机氮代谢产物的调节。在这里，我们已经鉴定了一个PII同源物(GLB1)在陶高等植物，拟南芥和蓖麻(蓖麻豆)。每种植物类PII蛋白与E.ColiPII有很高的总体同源性(50%)。Western印迹分析表明，该植物类PII蛋白是一种核编码的叶绿体蛋白。植物的类PII蛋白似乎在转录水平上受到调控，因为GLB1的mRNA水平受到光和代谢产物的影响。为了启动对拟南芥PII类蛋白在体内功能的研究，我们构建了PII表达不受其天然调控的转基因株系。对这些转基因植物的分析支持这样的观点，即植物坑状蛋白可能是一个复杂的信号转导网络的一部分，该网络参与感知碳和有机氮的状态，因此，在古生物、细菌和现在高等真核生物(植物)中发现的PII蛋白是已知的最广泛的调节蛋白之一，为在这三个生命区域分化之前可能存在的祖先代谢调节机制提供了证据。
PII is a protein allosteric effector in Escherichia coli and other bacteria that indirectly regulates glutamine synthetase at the transcriptional and post-translational levels in response to nitrogen availability. Data supporting the notion that plants have a nitrogen regulatory system(s) includes previous studies showing that the levels of mRNA for plant nitrogen assimilatory genes such as glutamine synthetase (GLN) and asparagine synthetase (ASN) are modulated by carbon and organic nitrogen metabolites. Here, we have characterized a PII homolog (GLB1) in tao higher plants, Arabidopsis thialiana and Ricinus communis (Castor bean). Each plant PII-like protein has high overall identity to E. coli PII (50%). Western blot analyses reveal that the plant PII-like protein is a nuclear-encoded chloroplast protein. The PII-like protein of plants appears to be regulated at the transcriptional level in that levels of GLB1 mRNA are affected by light and metabolites. To initiate studies of the in vivo function of the Arabidopsis PII-like protein, we have constructed transgenic lines in which PII expression is uncoupled from its native regulation. Analyses of these transgenic plants support the notion that the plant PIT-like protein may serve as part of a complex signal transduction network involved in perceiving the status of carbon and organic nitrogen, Thus, the PII protein found in archaea, bacteria, and now in higher eukaryotes (plants) is one of the most widespread regulatory proteins known, providing evidence for an ancestral metabolic regulatory mechanism that may have existed before the divergence of these three domains of life.