The primary transcriptome of the fast-growing cyanobacterium Synechococcus elongatus UTEX 2973

Xiaoming Tan,Stephan Klähn,Kuo Song,Xuefeng Lu,Wolfgang R Hess,Shengwei Hou,Jens Georg

doi:10.1186/s13068-018-1215-8

Abstract

BackgroundCyanobacteria have shown promising potential for the production of various biofuels and chemical feedstocks. Synechococcus elongatus UTEX 2973 is a fast-growing strain with pronounced tolerance to high temperatures and illumination. Hence, this strain appears to be ideal for the development of photosynthetic biotechnology. However, molecular insights on how this strain can rapidly accumulate biomass and carbohydrates under high-light and high-temperature conditions are lacking.ResultsDifferential RNA-Sequencing (dRNA-Seq) enabled the genome-wide identification of 4808 transcription start sites (TSSs) in S. elongatus UTEX 2973 using a background reduction algorithm. High light promoted the transcription of genes associated with central metabolic pathways, whereas the highly induced small RNA (sRNA) PsrR1 likely contributed to the repression of phycobilisome genes and the accelerated glycogen accumulation rates measured under this condition. Darkness caused transcriptome remodeling with a decline in the expression of genes for carbon fixation and other major metabolic pathways and an increase in the expression of genes for glycogen catabolism and Calvin cycle inhibitor CP12. Two of the identified TSSs drive the transcription of highly abundant sRNAs in darkness. One of them is widely conserved throughout the cyanobacterial phylum. Its gene is fused to a protein-coding gene in some species, illustrating the evolutionary origin of sRNAs from an mRNA 3′-end.ConclusionsOur comprehensive set of genome-wide mapped TSSs, sRNAs and promoter activities will be valuable for projects requiring precise information about the control of transcription aimed at metabolic engineering and the elucidation of stress acclimation mechanisms in this promising strain.

Highlights

Cyanobacteria have shown promising potential for the production of various biofuels and chemical feedstocks
After the introduction of a heterologous sucrose transporter, a mutant of S. elongatus University of Texas at Austin (UTEX) 2973 effectively secreted sucrose at a rate of 35.5 mg/L/h under salt stress conditions, proving that S. elongatus UTEX 2973 is a promising candidate to serve as a photosynthetic cell factory [5]
The primary transcriptome of Synechococcus elongatus UTEX 2973 Transcriptional start sites Total RNA was isolated from cells transferred to darkness or high light for 2 h, maintained at an elevated temperature for 30 min, or maintained in control conditions to identify active transcription start sites (TSSs) governing the transcriptome of S. elongatus UTEX 2973 under different conditions

Summary

Introduction

Cyanobacteria have shown promising potential for the production of various biofuels and chemical feedstocks. Synechococcus elongatus UTEX 2973 is a fast-growing strain with pronounced tolerance to high temperatures and illumination. This strain appears to be ideal for the development of photosynthetic biotechnology. Synechococcus elongatus UTEX 2973 is a recently characterized cyanobacterial strain with the fastest measured growth rate until now and good tolerance to high temperature and illumination [4]. This strain showed its fastest growth rate at 41 °C under continuous illumination of 500 μmol photons/m2/s, which is lethal to other popular model cyanobacterial strains, including Synechocystis sp. CRISPRCas mediated genomic engineering has been established in this strain, which will make metabolic engineering of S. elongatus UTEX 2973 more efficient in future [6]

Methods

Results

Discussion

Conclusion