Abstract
The tryptophan-rich sensory protein (TSPO) is a membrane protein, which is a member of the 18 kDa translocator protein/peripheral-type benzodiazepine receptor (MBR) family of proteins that is present in most organisms and is also referred to as Translocator protein 18 kDa. Although TSPO is associated with stress- and disease-related processes in organisms from bacteria to mammals, full elucidation of the functional role of the TSPO protein is lacking for most organisms in which it is found. In this study, we describe the regulation and function of a TSPO homolog in the cyanobacterium Fremyella diplosiphon, designated FdTSPO. Accumulation of the FdTSPO transcript is upregulated by green light and in response to nutrient deficiency and stress. A F. diplosiphon TSPO deletion mutant (i.e., ΔFdTSPO) showed altered responses compared to the wild type (WT) strain under stress conditions, including salt treatment, osmotic stress, and induced oxidative stress. Under salt stress, the FdTSPO transcript is upregulated and a ΔFdTSPO mutant accumulates lower levels of reactive oxygen species (ROS) and displays increased growth compared to WT. In response to osmotic stress, FdTSPO transcript levels are upregulated and ΔFdTSPO mutant cells exhibit impaired growth compared to the WT. By comparison, methyl viologen-induced oxidative stress results in higher ROS levels in the ΔFdTSPO mutant compared to the WT strain. Taken together, our results provide support for the involvement of membrane-localized FdTSPO in mediating cellular responses to stress in F. diplosiphon and represent detailed functional analysis of a cyanobacterial TSPO. This study advances our understanding of the functional roles of TSPO homologs in vivo.
Highlights
Cyanobacteria are capable of adapting to various environments as evident by their ubiquitous distribution in fresh and salt water bodies as well as arid areas (Whitton and Potts, 2000)
The level of sequence identity between some cyanobacterial tryptophan-rich sensory protein (TSPO) homologs and the distinct genomic contexts observed in different organisms (Figure 1) may be explained by varying organismal habitats and different types of chromatic acclimation found in the cyanobacteria phylum (Carr and Whitton, 1982; Whitton and Potts, 2000)
TSPO negatively affects photosynthetic pigment accumulation in Rhodobacter sphaeroides through negative regulation of transcription of carotenoid and bacteriochlorophyll biosynthesis genes, i.e., aerobically grown RsTSPO mutant cells have higher levels of carotenoids and bacteriochlorophyll than wild type (WT); whereas TSPO overexpression results in reduced pigment content compared to the WT (Yeliseev and Kaplan, 1995)
Summary
Cyanobacteria are capable of adapting to various environments as evident by their ubiquitous distribution in fresh and salt water bodies as well as arid areas (Whitton and Potts, 2000). These organisms exhibit developmental plasticity in response to environmental cues such as light and/or nutrients to tune growth and development to their environment. During CCA, the composition of PBSs is varied in this organism through transcriptional control of phycobiliprotein biosynthesis depending on the external light quality (Gutu and Kehoe, 2012). The phycobilin chromophores that confer the PBSs with their specific absorption characteristics are open-chain tetrapyrroles covalently attached to the phycobiliproteins (Frankenberg et al, 2001)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
