Characteristics of Pos19 – A Small Coding RNA in the Oxidative Stress Response of Rhodobacter sphaeroides

Abstract

The phototrophic bacterium Rhodobacter sphaeroides induces several small RNAs (sRNAs) when singlet oxygen (1O2) levels are elevated, a situation also referred to as photo-oxidative stress. An RNA-seq study identified the RSs0019 sRNA, which is renamed Pos19 (photo-oxidative stress induced sRNA 19). Pos19 is part of the RpoE regulon and consequently induced upon 1O2 and peroxide stress. The 219 nt long Pos19 transcript contains a small open reading frame (sORF) of 150 nt, which is translated in vivo. Over-expression of Pos19 results in reduced mRNA levels for several genes, of which numerous are involved in sulfur metabolism. The negative effect on the potential targets is maintained even when translation of the sORF is abolished, arguing that regulation is entailed by the sRNA itself. Reporter studies further revealed that regulation of the most affected mRNA, namely RSP_0557, by Pos19 is Hfq-dependent. Direct binding of Pos19 to Hfq was shown by co-immunoprecipitation. Physiological experiments indicated Pos19 to be involved in the balance of glutathione biosynthesis. Moreover, a lack of Pos19 leads to elevated reactive oxygen species levels. Taken together our data identify the sRNA Pos19 as a coding sRNA with a distinct expression pattern and potential role under oxidative stress in the phototrophic bacterium R. sphaeroides.

Dual-Function RNAs

“…Another potential dual-function sRNA in gram-negative bacteria is the sRNA RSs0019 in Rhodobacter sphaeroides . RSs0019 is produced in response to photo-oxidative stress however, no target mRNAs have been identified and translation of the 50 codon ORF has not been observed (79–81). …”

RNase E cleavage shapes the transcriptome ofRhodobacter sphaeroidesand strongly impacts phototrophic growth

“…RNA-Seq analyses were performed for the first time in 2009 in R. sphaeroides and allowed the identification of numerous sRNAs, some of them responding to oxidative or photooxidative stress ( Berghoff et al, 2009 ). An important function of such sRNAs in the photooxidative stress response is well documented ( Mank et al, 2013 ; Adnan et al, 2015 ; Billenkamp et al, 2015 ; Müller et al, 2016 ; Peng et al, 2016 ). The sRNA PcrZ is a key regulator of photosynthesis gene expression and is part of a regulatory circuit that balances expression of those genes in response to changing redox conditions.…”

PcrX, an sRNA derived from the 3′‐ UTR of the Rhodobacter sphaeroides puf operon modulates expression of puf genes encoding proteins of the bacterial photosynthetic apparatus

“…Bacteriochlorophyll can act as a photosensitizer that in presence of oxygen and light converts the ground-state triplet oxygen to the harmful singlet oxygen. As a consequence, R. sphaeroides has developed efficient defense mechanisms against singlet oxygen that are controlled by a network of regulatory proteins (reviewed in Glaeser et al, 2011;Berghoff and Klug 2016) and regulatory sRNAs (Adnan et al, 2015;Billenkamp et al, 2015;Peng et al, 2016;Müller et al, 2016). To reduce the risk of singlet oxygen generation R. sphaeroides has also developed sophisticated regulatory networks to control the formation of photosynthetic complexes in response to oxygen and light signals (reviewed in: Gregor and Klug 2002;Zeilstra-Ryalls and Kaplan 2004).…”