mRNA localization and thylakoid protein biogenesis in the filamentous heterocyst-forming cyanobacterium Anabaena sp. PCC 7120

作者：Kexin Wang, Moontaha Mahbub, Giulia Mastroianni, Ana Valladares, Conrad W. Mullineaux · 发表于：Journal of Bacteriology · 年份：2024 · DOI：10.1128/jb.00328-24 · 被引用次数：7 · 研究领域：Photosynthetic Processes and Mechanisms、Microbial Community Ecology and Physiology、Algal biology and biofuel production

ABSTRACT Heterocyst-forming cyanobacteria such as Anabaena ( Nostoc ) sp. PCC 7120 exhibit extensive remodeling of their thylakoid membranes during heterocyst differentiation. Here we investigate the sites of translation of thylakoid membrane proteins in Anabaena vegetative cells and developing heterocysts, using mRNA fluorescent in situ hybridization (FISH) to detect the location of specific mRNA species. We probed mRNAs encoding reaction center core components and the heterocyst-specific terminal oxidases Cox2 and Cox3. As in unicellular cyanobacteria, the mRNAs encoding membrane-integral thylakoid proteins are concentrated in patches at the inner face of the thylakoid membrane system, adjacent to the central cytoplasm. These patches mark the putative sites of translation and membrane insertion of these proteins. Oxidase activity in mature heterocysts is concentrated in the specialized “honeycomb” regions of the thylakoid membranes close to the cell poles. However, cox2 and cox3 mRNAs remain evenly distributed over the inner face of the thylakoids, implying that oxidase proteins migrate extensively after translation to reach their destination in the honeycomb membranes. The RNA-binding protein RbpG is the closest Anabaena homolog of Rbp3 in the unicellular cyanobacterium Synechocystis sp. PCC 6803, which we previously showed to be crucial for the correct location of photosynthetic mRNAs. An rbpG null mutant shows decreased cellular levels of photosynthetic mRNAs and photosy...