de Porcellinis Alice J, Klähn Stephan, Rosgaard Lisa, Kirsch Rebekka, Gutekunst Kirstin, Georg Jens, Hess Wolfgang R, Sakuragi Yumiko
Copenhagen Plant Science Center, Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Frederiksberg, DK-1871, Denmark.
These authors contributed equally to this work.
Plant Cell Physiol. 2016 Oct;57(10):2091-2103. doi: 10.1093/pcp/pcw128. Epub 2016 Jul 20.
Carbohydrate metabolism is a tightly regulated process in photosynthetic organisms. In the cyanobacterium Synechocystis sp. PCC 6803, the photomixotrophic growth protein A (PmgA) is involved in the regulation of glucose and storage carbohydrate (i.e. glycogen) metabolism, while its biochemical activity and possible factors acting downstream of PmgA are unknown. Here, a genome-wide microarray analysis of a ΔpmgA strain identified the expression of 36 protein-coding genes and 42 non-coding transcripts as significantly altered. From these, the non-coding RNA Ncr0700 was identified as the transcript most strongly reduced in abundance. Ncr0700 is widely conserved among cyanobacteria. In Synechocystis its expression is inversely correlated with light intensity. Similarly to a ΔpmgA mutant, a Δncr0700 deletion strain showed an approximately 2-fold increase in glycogen content under photoautotrophic conditions and wild-type-like growth. Moreover, its growth was arrested by 38 h after a shift to photomixotrophic conditions. Ectopic expression of Ncr0700 in Δncr0700 and ΔpmgA restored the glycogen content and photomixotrophic growth to wild-type levels. These results indicate that Ncr0700 is required for photomixotrophic growth and the regulation of glycogen accumulation, and acts downstream of PmgA. Hence Ncr0700 is renamed here as PmgR1 for photomixotrophic growth RNA 1.
碳水化合物代谢是光合生物中一个受到严格调控的过程。在蓝藻集胞藻6803中，光合兼养生长蛋白A（PmgA）参与葡萄糖和储存碳水化合物（即糖原）代谢的调控，但其生化活性以及可能在PmgA下游起作用的因子尚不清楚。在此，对ΔpmgA菌株进行全基因组微阵列分析，确定36个蛋白质编码基因和42个非编码转录本的表达发生了显著变化。从这些结果中，非编码RNA Ncr0700被确定为丰度降低最显著的转录本。Ncr0700在蓝藻中广泛保守。在集胞藻中，其表达与光照强度呈负相关。与ΔpmgA突变体类似，Δncr0700缺失菌株在光合自养条件下糖原含量增加了约2倍，且生长类似野生型。此外，在转变为光合兼养条件后38小时，其生长停止。在Δncr0700和ΔpmgA中异位表达Ncr0700可使糖原含量和光合兼养生长恢复到野生型水平。这些结果表明，Ncr0700是光合兼养生长和糖原积累调控所必需的，且在PmgA下游起作用。因此，在此将Ncr0700重新命名为光合兼养生长RNA 1（PmgR1）。
