PipX对聚球藻PCC7942中ABC型氰酸盐转运蛋白CYT的调控及其分子机理研究

Cyanobacteria exhibit a great capacity to adapt to different environmental conditions, and are one of the largest and most important groups of bacteria on earth. Nitrogen assimilation in cyanobacteria plays a key role for the nitrogen cycle on earth, and organic nitrogen cyanate can be used as nitrogen source for Synechococcus elongatus strain PCC 7942 to meet their physiological requirements under nitrogen-deficient conditions. Our previous studies indicated that the PII protein, which forms a complex with PipX, is required for the regulation of ABC-type cyanate transporter(CYT). However, the mechanism of the regulation of CYT remains unknown. Therefore, the objective of the present study was to determine whether PipX was also involved in the regulation of ABC-type CYT. Fortunately, three mutants of PipX- single mutant, PII- single mutant and PipX-/PII- double mutant were successfully constructed in our previous work. In present study, three mutants will be used to clarify the mechanism of the regulation of CYT in cyanobacteria from different perspectives of growth characteristics, physiological and biochemical responses, gene and protein expression. The results should be important to understand the expression and regulation of the genes and enzymes initiated under nitrogen deficient conditions for maintaining their life activities, and also to understand the mechanism of cyanobacteria adaptation to extreme conditions.

蓝藻具有很强的环境适应能力，是地球上规模最大、最重要的微生物之一，对地球氮循环至关重要。在氮元素匮乏的环境中，聚球藻PCC7942可通过ABC型氰酸盐转运蛋白CYT利用环境中的有机态氮源氰酸盐，以满足其对氮元素的生命需求，这对蓝藻的环境适应能力非常重要。我们前期的研究发现，在聚球藻PCC7942中，PipX的结合蛋白PII对ABC型氰酸盐转运蛋白CYT具有不完全的调控功能，那么PipX是否对ABC型CYT也存在调控功能？针对这一学术问题，本项目在已成功构建的PipX-单突变株、PII-单突变株和PipX-/PII-双突变株的基础上，通过对这三突变体同步对比研究，从生长特性、生理生化响应、基因和蛋白水平等角度探究PipX对蓝藻ABC型氰酸盐转运蛋白的调控功能和内在机理，旨在了解蓝藻在氮素匮乏的极端环境中为维持其生命活动所启动的基因和酶的表达及调控以及适应此环境的机理。