Singh Abhay K, Elvitigala Thanura, Bhattacharyya-Pakrasi Maitrayee, Aurora Rajeev, Ghosh Bijoy, Pakrasi Himadri B
Department of Biology , Washington University, St. Louis, Missouri 63130, USA.
Plant Physiol. 2008 Sep;148(1):467-78. doi: 10.1104/pp.108.123489. Epub 2008 Jul 3.
Light drives the production of chemical energy and reducing equivalents in photosynthetic organisms required for the assimilation of essential nutrients. This process also generates strong oxidants and reductants that can be damaging to the cellular processes, especially during absorption of excess excitation energy. Cyanobacteria, like other oxygenic photosynthetic organisms, respond to increases in the excitation energy, such as during exposure of cells to high light (HL) by the reduction of antenna size and photosystem content. However, the mechanism of how Synechocystis sp. PCC 6803, a cyanobacterium, maintains redox homeostasis and coordinates various metabolic processes under HL stress remains poorly understood. In this study, we have utilized time series transcriptome data to elucidate the global responses of Synechocystis to HL. Identification of differentially regulated genes involved in the regulation, protection, and maintenance of redox homeostasis has offered important insights into the optimized response of Synechocystis to HL. Our results indicate a comprehensive integrated homeostatic interaction between energy production (photosynthesis) and energy consumption (assimilation of carbon and nitrogen). In addition, measurements of physiological parameters under different growth conditions showed that integration between the two processes is not a consequence of limitations in the external carbon and nitrogen levels available to the cells. We have also discovered the existence of a novel glycosylation pathway, to date known as an important nutrient sensor only in eukaryotes. Up-regulation of a gene encoding the rate-limiting enzyme in the hexosamine pathway suggests a regulatory role for protein glycosylation in Synechocystis under HL.
光驱动光合生物中化学能的产生以及同化必需营养物质所需的还原当量。这个过程还会产生强氧化剂和还原剂，它们可能会损害细胞过程，尤其是在吸收过量激发能期间。与其他产氧光合生物一样，蓝细菌会通过减小天线大小和光系统含量来应对激发能的增加，例如细胞暴露于高光（HL）时。然而，集胞藻PCC 6803这种蓝细菌在高光胁迫下如何维持氧化还原稳态并协调各种代谢过程的机制仍知之甚少。在本研究中，我们利用时间序列转录组数据来阐明集胞藻对高光的全局响应。鉴定参与氧化还原稳态调节、保护和维持的差异调节基因，为集胞藻对高光的优化响应提供了重要见解。我们的结果表明能量产生（光合作用）和能量消耗（碳和氮的同化）之间存在全面的综合稳态相互作用。此外，在不同生长条件下对生理参数的测量表明，这两个过程之间 的整合不是细胞可用的外部碳和氮水平受限的结果。我们还发现了一种新的糖基化途径，迄今为止仅在真核生物中作为一种重要的营养传感器为人所知。己糖胺途径中编码限速酶的基因上调表明蛋白质糖基化在高光下的集胞藻中具有调节作用。
