The two Dps proteins, NpDps2 and NpDps5, are involved in light-induced oxidative stress tolerance in the N2-fixing cyanobacterium Nostoc punctiforme

Abstract

Cyanobacteria are photosynthetic prokaryotes that are considered biotechnologically prominent organisms for production of high-value compounds. Cyanobacteria are subject to high-light intensities, which is a challenge that needs to be addressed in design of efficient bio-engineered photosynthetic organisms. Dps proteins are members of the ferritin superfamily and are omnipresent in prokaryotes. They play a major role in oxidative stress protection and iron homeostasis. The filamentous, heterocyst-forming Nostoc punctiforme, has five Dps proteins. In this study we elucidated the role of these Dps proteins in acclimation to high light intensity, the gene loci organization and the transcriptional regulation of all five dps genes in N. punctiforme was revealed, and dps-deletion mutant strains were used in physiological characterization. Two mutants defective in Dps2 and Dps5 activity displayed a reduced fitness under increased illumination, as well as a differential Photosystem (PS) stoichiometry, with an elevated Photosystem II to Photosystem I ratio in the dps5 deletion strain. This work establishes a Dps-mediated link between light tolerance, HO detoxification, and iron homeostasis, and provides further evidence on the non-redundant role of multiple Dps proteins in this multicellular cyanobacterium.

An optogenetic toolbox of LOV-based photosensitizers for light-driven killing of bacteria

“…However, the strongest induction was observed for the dps gene (~28-fold), which codes for the “ D NA-binding p rotein from s tarved cells” (Dps) that is known to protect DNA against ROS-mediated damage in E . coli and other bacteria 80 – 83 . Furthermore, most of the suf genes are induced via DsFbFP M49I-dependent ROS formation.…”

Ferritin, cellular iron storage and regulation

“…BFR from Pseudomonas aeruginosa needs the presence of the ferrodoxin encoded by the neighboring gene Bfd for a fast reductive iron release in vitro . The N 2 ‐fixing cyanobacterium Nostoc puntiforme has 5 Dps and only two of them are important for fitness under high illumination and differentiation photosystem . The function of the encapsulin EncFtn as iron storage molecule so far has been observed only in vivo.…”

Differential biochemical properties of three canonical Dps proteins from the cyanobacterium Nostoc punctiforme suggest distinct cellular functions

“…However, the specific functions of the individual Dps and cooperative behavior of multiple Dps proteins within one organism for cellular fitness, including iron homeostasis and oxidative stress tolerance, have not been resolved. As previously mentioned, the working hypothesis of our earlier studies was that multiple Dps proteins within one organism have different and specific function of importance for cell homeostasis (8,21), and that these differences would be reflected in the biochemical properties of the individual Dps. The results obtained in the present in vitro and in silico studies indeed show clear differences in the individual biochemical properties of the three canonical Dps proteins NpDps1, NpDps2, and NpDps3, as summarized in Table 2.…”

“…This might seem contradictory to our earlier functional genetics studies in which only one of the three, NpDps2, was shown to have a crucial physiological role in the presence of high exogenously added H 2 O 2 levels (8). However, although the physiological relevance of the iron uptake and iron oxidation by H 2 O 2 is hard to predict, the in vivo roles could to some extent be understood by the determined differential gene and protein expression of NpDps (8,9,21,45,46). The NpDps-specific expression is distributed among the various cell types, formed during specific cultivation conditions, of N. punctiforme (12), which suggests growth condition-specific functions of the three canonical NpDps proteins.…”