ROSE elements occur in disparate rhizobia and are functionally interchangeable between species

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• The regulation of heat shock gene expression is crucial for bacterial survival under stress.
• Small heat shock proteins (sHsps) play a vital role in cellular protection during thermal stress.
• The ROSE (repression of heat shock gene expression) element controls gene expression in Bradyrhizobium japonicum.

Purpose of the Study:

• To investigate the presence and function of ROSE elements in various rhizobia species.
• To determine if the regulatory mechanism conferred by ROSE elements is conserved across different rhizobia.
• To provide genetic evidence for multiple sHsps in these organisms.

Main Methods:

• Sequence alignment of ROSE elements from different rhizobia.
• Primer-extension analysis to study transcription of ROSE-associated operons.
• Construction and analysis of translational ROSE-hsp'-'lacZ fusions in B. japonicum.

Main Results:

• ROSE elements are present in Bradyrhizobium sp. (Parasponia), Rhizobium sp. strain NGR234, and Mesorhizobium loti, in addition to B. japonicum.
• A conserved region within the ROSE element suggests functional importance.
• Transcription of ROSE-controlled operons is repressed at low temperatures and induced upon temperature upshift.
• Heterologous ROSE elements from other rhizobia species confer heat-responsiveness when integrated into B. japonicum.

Conclusions:

• The ROSE regulatory element and its function in controlling heat shock gene expression are conserved among various rhizobia species.
• This conserved regulatory principle highlights a common adaptation strategy in rhizobia.
• The findings support the presence of multiple sHsps in these bacterial groups.