The Non-Coding RNA Ncr0700/PmgR1 is Required for Photomixotrophic Growth and the Regulation of Glycogen Accumulation in the CyanobacteriumSynechocystissp. PCC 6803

Abstract

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.

Pooled CRISPRi screening of the cyanobacterium Synechocystis sp PCC 6803 for enhanced industrial phenotypes

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Analysis of a photosynthetic cyanobacterium rich in internal membrane systems via gradient profiling by sequencing (Grad-seq)

“…The data permit for the first time the identification of candidate RNA-binding proteins involved in the formation of major RNA-protein complexes in this group of bacteria. Although Synechocystis expresses multiple sRNAs of crucial relevance for oxygenic photosynthesis and other important physiological processes(Klähn et al, 2015;Georg et al, 2017Georg et al, , 2014de Porcellinis et al, 2016), homologs of CsrA, ProQ or Hfq do not exist in cyanobacteria or are not…”

6S RNA supports recovery from nitrogen depletion inSynechocystissp. PCC 6803

“…In addition to protein-coding genes, a few small non-coding RNAs (sRNAs) showed altered levels in the mutant, including the previously characterized PmgR [48], NsiR4 [49] and PsrR1 [11], as well as several hypothetical riboregulators that were identified by differential RNA sequencing (dRNA-seq) [50]. Among these transcripts, SyR11 exhibited the most diverging accumulation kinetics ( Fig.…”