The Small RNA-Binding Protein CcaF1 Promotes Formation of Photosynthetic Complexes in Rhodobacter sphaeroides

Abstract

In natural habitats, bacteria frequently need to adapt to changing environmental conditions. Regulation of transcription plays an important role in this process. However, riboregulation also contributes substantially to adaptation. Riboregulation often acts at the level of mRNA stability, which is determined by sRNAs, RNases, and RNA-binding proteins. We previously identified the small RNA-binding protein CcaF1, which is involved in sRNA maturation and RNA turnover in Rhodobacter sphaeroides. Rhodobacter is a facultative phototroph that can perform aerobic and anaerobic respiration, fermentation, and anoxygenic photosynthesis. Oxygen concentration and light conditions decide the pathway for ATP production. Here, we show that CcaF1 promotes the formation of photosynthetic complexes by increasing levels of mRNAs for pigment synthesis and for some pigment-binding proteins. Levels of mRNAs for transcriptional regulators of photosynthesis genes are not affected by CcaF1. RIP-Seq analysis compares the binding of CcaF1 to RNAs during microaerobic and photosynthetic growth. The stability of the pufBA mRNA for proteins of the light-harvesting I complex is increased by CcaF1 during phototrophic growth but decreased during microaerobic growth. This research underlines the importance of RNA-binding proteins in adaptation to different environments and demonstrates that an RNA-binding protein can differentially affect its binding partners in dependence upon growth conditions.

RNase III participates in control of quorum sensing, pigmentation and oxidative stress resistance in Rhodobacter sphaeroides

“…Recent studies of our group identified a novel small RNA‐binding protein, CcaF1, which is co‐expressed with four homologous CcsR sRNAs (CcsR1‐4) from a single promoter (Billenkamp et al, 2015; Grützner, Billenkamp, et al, 2021). While CcaF1 binds to various RNA targets (Grützner, et al, 2023; Grützner, Billenkamp, et al, 2021), affecting their stability and regulating gene expression, the CcsR sRNAs inhibit a glutathione‐dependent C1 metabolic pathway, leading to increased levels of antioxidative glutathione, which provides protection against reactive oxygen species and enhancing cell viability. Previous work documented a direct correlation between CcsR levels and stress resistance (Billenkamp et al, 2015; Grützner, Billenkamp, et al, 2021).…”

“…We recently showed that the small RNA‐binding DUF1127‐domain protein CcaF1 promotes the formation of photosynthesis complexes in R. sphaeroides (Grützner et al, 2023). ccaF1 is co‐transcribed with the CcsR sRNAs and also shows higher levels in the rnc − mutant.…”