# Defining the networks that connect RNase III and RNase J-mediated regulation of primary and specialized metabolism in Streptomyces venezuelae

## TL;DR

This study explores how two ribonucleases, RNase III and RNase J, regulate gene expression and metabolism in Streptomyces venezuelae, revealing their roles in development and antibiotic production.

## Contribution

The paper identifies distinct and cooperative roles of RNase III and RNase J in regulating gene expression and metabolism in Streptomyces.

## Key findings

- RNase III and RNase J mutants show dysregulation of the BldD regulon and altered expression of cyclic-di-GMP-associated enzymes.
- RNase III directly targets PhoP regulon members, linking RNA metabolism to phosphate regulation and antibiotic production.
- RNase J targets ribosomal protein transcripts, impacting translation and gene expression dynamics.

## Abstract

RNA metabolism involves coordinating RNA synthesis with RNA processing and degradation. Ribonucleases play fundamental roles within the cell, contributing to the cleavage, modification, and degradation of RNA molecules, with these actions ensuring appropriate gene regulation and cellular homeostasis. Here, we employed RNA sequencing to explore the impact of RNase III and RNase J on the transcriptome of Streptomyces venezuelae. Differential expression analysis comparing wild-type and RNase mutant strains at distinct developmental stages revealed significant changes in transcript abundance, particularly in pathways related to multicellular development, nutrient acquisition, and specialized metabolism. Both RNase mutants exhibited dysregulation of the BldD regulon, including altered expression of many cyclic-di-GMP-associated enzymes. We also observed precocious chloramphenicol production in these RNase mutants and found that in the RNase III mutant, this was associated with PhoP-mediated regulation. We further found that RNase III directly targeted members of the PhoP regulon, suggesting a link between RNA metabolism and a regulator that bridges primary and specialized metabolism. We connected RNase J function with translation through the observation that RNase J directly targets multiple ribosomal protein transcripts for degradation. These findings establish distinct but complementary roles for RNase III and RNase J in coordinating the gene expression dynamics critical for S. venezuelae development and specialized metabolism.

RNA processing and metabolism are mediated by ribonucleases and are fundamental processes in all cells. In the morphologically complex and metabolically sophisticated Streptomyces bacteria, RNase III and RNase J influence both development and metabolism through poorly understood mechanisms. Here, we show that both ribonucleases are required for the proper expression of the BldD developmental pathway and contribute to the control of chloramphenicol production, with an interesting connection to phosphate regulation for RNase III. Additionally, we show that both RNases have the potential to impact translation through distinct mechanisms and can function cooperatively in degrading specific transcripts. This study advances our understanding of RNases in Streptomyces biology by providing insight into distinct contributions made by these enzymes and the intriguing interplay between them.