The Recent Evolution of a Symbiotic Ion Channel in the Legume Family Altered Ion Conductance and Improved Functionality in Calcium Signaling[C][W]
The Recent Evolution of a Symbiotic Ion Channel in the Legume Family Altered Ion Conductance and Improved Functionality in Calcium Signaling[C][W]
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DOI：
10.1105/tpc.112.098475
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发表时间：
2012-06
期刊：
影响因子：
11.6
通讯作者：
Muthusubramanian Venkateshwaran;Ana M Cosme;Lu Han;M. Banba;K. Satyshur;E. Schleiff;M. Parniske;H. Imaizumi-Anraku;Jean-Michel Ané
中科院分区：
文献类型：
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作者：
Muthusubramanian Venkateshwaran;Ana M Cosme;Lu Han;M. Banba;K. Satyshur;E. Schleiff;M. Parniske;H. Imaizumi-Anraku;Jean-Michel Ané
两个相似但不冗余的离子通道（CASTOR和POLLUX）是被子植物共生信号转导所必需的。最近在豆科植物中出现了一个单氨基酸取代的现象。这种突变改变了污染性并改善了它的功能，同时使CASTOR在相应的豆科植物部落中处于次要地位。丛枝菌根和根瘤菌-豆科植物共生是促进植物营养的两种主要的根内共生。在日本莲中，两个共生阳离子通道CASTOR和POLLUX在诱导核钙尖刺中不可或缺，而核钙尖刺是植物对共生伴侣识别的最早反应之一。在最近的进化过程中，在密切相关的短形紫花苜蓿（Medicago truncatula）中，一个被认为是poloxx同源基因的氨基酸替换使得通道单独存在，足以实现共生；L. japonicus的castor、污染型和castor污染型双突变体均可由DMI1单独拯救，而M. truncatula的DMI1突变体需由Lj-CASTOR和lj -污染型共同拯救。Lj-POLLUX选择性过滤器中的丙氨酸替代关键丝氨酸的实验赋予了与DMI1难以区分的共生性能。在表达DMI1的人胚胎肾-293细胞（野生型和突变型）中，通过平面脂质双分子层实验结合钙显像对DMI1和Lj-CASTOR（野生型和突变型）进行电生理表征表明，丝氨酸到丙氨酸的取代使DMI1的电导降低并处于长开放状态，提高了其介导钙振荡的效率。我们认为，选择性过滤器中的这种单一氨基酸替换使DMI1单独存在足以实现共生，从而在机制水平上解释了该等位基因的选择优势。
Two similar but not redundant ion channels (CASTOR and POLLUX) are required for the transduction of symbiotic signals in angiosperms. A single amino acid substitution in the filter region of POLLUX occurred recently in the legume family. This mutation altered POLLUX conductance and improved its functionality, while relegating CASTOR to a minor role in the corresponding legume tribes. Arbuscular mycorrhiza and the rhizobia-legume symbiosis are two major root endosymbioses that facilitate plant nutrition. In Lotus japonicus, two symbiotic cation channels, CASTOR and POLLUX, are indispensable for the induction of nuclear calcium spiking, one of the earliest plant responses to symbiotic partner recognition. During recent evolution, a single amino acid substitution in DOES NOT MAKE INFECTIONS1 (DMI1), the POLLUX putative ortholog in the closely related Medicago truncatula, rendered the channel solo sufficient for symbiosis; castor, pollux, and castor pollux double mutants of L. japonicus were rescued by DMI1 alone, while both Lj-CASTOR and Lj-POLLUX were required for rescuing a dmi1 mutant of M. truncatula. Experimental replacement of the critical serine by an alanine in the selectivity filter of Lj-POLLUX conferred a symbiotic performance indistinguishable from DMI1. Electrophysiological characterization of DMI1 and Lj-CASTOR (wild-type and mutants) by planar lipid bilayer experiments combined with calcium imaging in Human Embryonic Kidney-293 cells expressing DMI1 (the wild type and mutants) suggest that the serine-to-alanine substitution conferred reduced conductance with a long open state to DMI1 and improved its efficiency in mediating calcium oscillations. We propose that this single amino acid replacement in the selectivity filter made DMI1 solo sufficient for symbiosis, thus explaining the selective advantage of this allele at the mechanistic level.