Transcriptional Activation of Glycogen Catabolism and the Oxidative Pentose Phosphate Pathway by NrrA Facilitates Cell Survival Under Nitrogen Starvation in the Cyanobacterium Synechococcus sp. Strain PCC 7002
Transcriptional Activation of Glycogen Catabolism and the Oxidative Pentose Phosphate Pathway by NrrA Facilitates Cell Survival Under Nitrogen Starvation in the Cyanobacterium Synechococcus sp. Strain PCC 7002
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DOI：
10.1093/pcp/pcy059
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发表时间：
2018-06
影响因子：
4.9
通讯作者：
Yuka Shimmori;Y. Kanesaki;M. Nozawa;H. Yoshikawa;S. Ehira
中科院分区：
文献类型：
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作者：
Yuka Shimmori;Y. Kanesaki;M. Nozawa;H. Yoshikawa;S. Ehira
蓝藻通过改变细胞代谢来应对氮的剥夺。在氮饥饿期间，糖原在细胞内积累以吸收多余的碳和能量，抑制糖原合成导致氮反应受损和生存能力下降。尽管糖原积累，但与糖原分解代谢相关的基因在氮剥夺下上调。在这项研究中，我们发现糖原分解代谢也参与了蓝细菌聚藻球菌（Synechococcus sp. PCC 7002）对氮剥夺的适应。编码糖原磷酸化酶的glgP2基因受氮剥夺诱导，其表达受氮调节反应调控因子A （NrrA）调控，NrrA是蓝藻中高度保守的转录调控因子。在无氮条件下，糖原磷酸化酶的激活被nrrA基因的破坏所破坏，nrrA突变体的存活率下降。此外，glgP2突变体对氮饥饿非常敏感。NrrA还调节tal-zwf-opcA操纵子的表达，该操纵子编码氧化戊糖磷酸（OPP）途径的酶，而葡萄糖-6-磷酸脱氢酶（OPP途径的第一酶）的失活，降低了氮饥饿下的生存能力。由此可见，NrrA在缺氧条件下通过激活糖原降解和OPP通路促进细胞存活。
Cyanobacteria respond to nitrogen deprivation by changing cellular metabolism. Glycogen is accumulated within cells to assimilate excess carbon and energy during nitrogen starvation, and inhibition of glycogen synthesis results in impaired nitrogen response and decreased ability to survive. In spite of glycogen accumulation, genes related to glycogen catabolism are up-regulated by nitrogen deprivation. In this study, we found that glycogen catabolism was also involved in acclimation to nitrogen deprivation in the cyanobacterium Synechococcus sp. PCC 7002. The glgP2 gene, encoding glycogen phosphorylase, was induced by nitrogen deprivation, and its expression was regulated by the nitrogen-regulated response regulator A (NrrA), which is a highly conserved transcriptional regulator in cyanobacteria. Activation of glycogen phosphorylase under nitrogen-deprived conditions was abolished by disruption of the nrrA gene, and survival of the nrrA mutant declined. In addition, a glgP2 mutant was highly susceptible to nitrogen starvation. NrrA also regulated expression of the tal-zwf-opcA operon, encoding enzymes of the oxidative pentose phosphate (OPP) pathway, and inactivation of glucose-6-phosphate dehydrogenase, the first enzyme of the OPP pathway, decreased the ability to survive under nitrogen starvation. It was concluded that NrrA facilitates cell survival by activating glycogen degradation and the OPP pathway under nitrogen-deprived conditions.