Vegetative cells may perform nitrogen fixation function under nitrogen deprivation in Anabaena sp. strain PCC 7120 based on genome-wide differential expression analysis

Abstract

Nitrogen assimilation is strictly regulated in cyanobacteria. In an inorganic nitrogen-deficient environment, some vegetative cells of the cyanobacterium Anabaena differentiate into heterocysts. We assessed the photosynthesis and nitrogen-fixing capacities of heterocysts and vegetative cells, respectively, at the transcriptome level. RNA extracted from nitrogen-replete vegetative cells (NVs), nitrogen-deprived vegetative cells (NDVs), and nitrogen-deprived heterocysts (NDHs) in Anabaena sp. strain PCC 7120 was evaluated by transcriptome sequencing. Paired comparisons of NVs vs. NDHs, NVs vs. NDVs, and NDVs vs. NDHs revealed 2,044 differentially expressed genes (DEGs). Kyoto Encyclopedia of Genes and Genomes enrichment analysis of the DEGs showed that carbon fixation in photosynthetic organisms and several nitrogen metabolism-related pathways were significantly enriched. Synthesis of Gvp (Gas vesicle synthesis protein gene) in NVs was blocked by nitrogen deprivation, which may cause Anabaena cells to sink and promote nitrogen fixation under anaerobic conditions; in contrast, heterocysts may perform photosynthesis under nitrogen deprivation conditions, whereas the nitrogen fixation capability of vegetative cells was promoted by nitrogen deprivation. Immunofluorescence analysis of nitrogenase iron protein suggested that the nitrogen fixation capability of vegetative cells was promoted by nitrogen deprivation. Our findings provide insight into the molecular mechanisms underlying nitrogen fixation and photosynthesis in vegetative cells and heterocysts at the transcriptome level. This study provides a foundation for further functional verification of heterocyst growth, differentiation, and water bloom control.

Evaluation of Ecotoxicity of Nanoceria to Organisms of Different Trophic Levels

“…From (Fig. 6), it is evident that nanoceria from 100 mg L -1 there was a degeneration of vegetative tissue, which may affect the nitrogen fixation process in Anabaena (He et al, 2021). Also, the heterocyst frequency reduced with 100 mg L -1 nanoceria concentration (Fig.…”

Rapid Recovery of Buoyancy in Eutrophic Environments Indicates That Cyanobacterial Blooms Cannot Be Effectively Controlled by Simply Collapsing Gas Vesicles Alone

“…On the other hand, for non-nitrogen-fixing cyanobacteria, nitrogen-limited environments significantly inhibited the recovery of floating capacity. The gvp gene cluster is a key gene that regulates gas vesicle synthesis, and nitrogen-limited environments block the synthesis of gvp [26,27]. Furthermore, studies have shown that the gas vesicle consists of a single layer of the 7-8 kDa protein gas vesicle protein A (GvpA), and nitrogen is an important component for protein synthesis [16,28].…”

Phytostimulants in sustainable agriculture

“…The formation of soil crust in cultivated cyanobacteria field can avoid the runoff and therefore reduces the risk of water contamination with nitrogen. Anabaena species has the ability to fix nitrogen even under nitrogen deprived environment (He et al, 2021). In modern agriculture practices, cyanobacteria could be used as biofertilizer as they provide 70-75% fixed N to agriculture system (Berthelot et al, 2015;Klawonn et al, 2016).…”