A stress-induced small RNA modulates alpha-rhizobial cell cycle progression

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Microbial survival depends on mechanisms regulating replication initiation and cell cycle progression.
• Small non-coding RNAs (sRNAs) are increasingly recognized as key regulators in bacteria.
• The plant-symbiotic bacterium Sinorhizobium meliloti provides a model for studying bacterial adaptation.

Purpose of the Study:

• To functionally characterize the trans-encoded small non-coding RNA (trans-sRNA) EcpR1 in Sinorhizobium meliloti.
• To investigate the role of EcpR1 in cell cycle regulation and microbial survival under stress conditions.
• To identify and validate mRNA targets of EcpR1.

Main Methods:

• Bioinformatic prediction of sRNA structure and targets.
• Gene expression analysis using two-plasmid differential gene expression assays.
• Analysis of bacterial growth, cell morphology, and DNA content.
• Assessment of bacterial competitiveness in planta.
• Investigation of mRNA degradation pathways.

Main Results:

• EcpR1 is a conserved trans-sRNA in Rhizobiales, forming a stable structure with two stem-loop domains.
• EcpR1 expression is induced by stress and stationary phase, and its overproduction causes cell elongation and increased DNA content.
• Deletion of EcpR1 leads to reduced competitiveness, suggesting a role in adaptation.
• EcpR1 post-transcriptionally represses cell cycle genes gcrA and dnaA via base-pairing with its conserved loop 1.
• EcpR1 promotes RNase E-dependent degradation of dnaA mRNA.

Conclusions:

• EcpR1 is a novel riboregulator involved in modulating cell cycle progression in Sinorhizobium meliloti.
• EcpR1 contributes to bacterial adaptation and survival under detrimental environmental conditions.
• The findings highlight the importance of trans-sRNAs in bacterial stress response and cell cycle control.