Does 2-phosphoglycolate serve as an internal signal molecule of inorganic carbon deprivation in the cyanobacterium Synechocystis sp PCC 6803?
Does 2-phosphoglycolate serve as an internal signal molecule of inorganic carbon deprivation in the cyanobacterium Synechocystis sp PCC 6803?
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DOI：
10.1111/1462-2920.12638
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发表时间：
2015-05-01
影响因子：
5.1
通讯作者：
Kaplan, Aaron
中科院分区：
文献类型：
--
作者：
Haimovich-Dayan, Maya;Lieman-Hurwitz, Judy;Kaplan, Aaron
蓝藻具有二氧化碳浓缩机制（CCM），这在功能上弥补了它们的核酮糖-1,5-二磷酸羧化酶/加氧酶（Rubisco）对二氧化碳的亲和力较差。本文认为，在限制CO2水平（LC）条件下，由Rubisco加氧酶活性产生并通过光呼吸途径代谢的2-磷酸乙醇酸（2-phosphoglycolate, 2PG）是诱导ccm相关基因的信号分子。然而，体内证据仍然缺失。由于2PG不能渗透到细胞中，我们控制了它的内部浓度。在蓝细菌SynechocystisPCC 6803中鉴定出4个可能编码磷酸乙醇酸磷酸酶（pgases）的基因（slr0458、sll1349、slr0586和slr1762）。slr0458在大肠杆菌中的表达导致PGPase活性显著升高。构建了一个过表达（OE） slr0458的胞囊菌突变体。与野生型（WT）相比，在限制CO2浓度下，突变体生长较慢，胞内2PG水平明显低于野生型，LC诱导基因cmpA、sbtA和ndhF3的转录丰度降低，OE细胞对LC的适应较慢，表现为对无机碳的表观光合亲和力的延迟上升。这里获得的数据暗示2PG在这种蓝藻对LC的驯化中，但也表明其他尚未确定的成分也参与其中。
Cyanobacteria possess CO2-concentrating mechanisms (CCM) that functionally compensate for the poor affinity of their ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) to CO2. It was proposed that 2-phosphoglycolate (2PG), produced by the oxygenase activity of Rubisco and metabolized via photorespiratory routes, serves as a signal molecule for the induction of CCM-related genes under limiting CO2 level (LC) conditions. However, in vivo evidence is still missing. Since 2PG does not permeate the cells, we manipulated its internal concentration. Four putative phosphoglycolate phosphatases (PGPases) encoding genes (slr0458, sll1349, slr0586 and slr1762) were identified in the cyanobacterium SynechocystisPCC 6803. Expression of slr0458 in Escherichia coli led to a significant rise in PGPase activity. A Synechocystis mutant overexpressing (OE) slr0458 was constructed. Compared with the wild type (WT), the mutant grew slower under limiting CO2 concentration and the intracellular 2PG level was considerably smaller than in the wild type, the transcript abundance of LC-induced genes including cmpA, sbtA and ndhF3 was reduced, and the OE cells acclimated slower to LC - indicated by the delayed rise in the apparent photosynthetic affinity to inorganic carbon. Data obtained here implicated 2PG in the acclimation of this cyanobacterium to LC but also indicated that other, yet to be identified components, are involved.