Dataset Information

Coordination of cyanobacterial nitrate assimilation and photosynthesis by a novel PsbO-interacting protein PirN

ABSTRACT: Nitrogen assimilation relies on photosynthetically-produced energy and reducing equivalents. Here, we identify a small protein, PsbO-interacting regulator of nitrate assimilation (PirN), as a key coordinator of photosynthesis and nitrate assimilation in Synechocystis sp. PCC 6803 (Synechocystis). PirN specifically accumulates under nitrate conditions and interacts with the photosystem II (PSII) subunit PsbO. Deletion of pirN (ΔpirN) under nitrate impairs growth, reduces PSII contents and oxygen evolution, and upregulates most nitrogen transport and assimilation proteins except the nitrate reductase NarB, mimicking nitrogen starvation response likely due to impaired nitrate reduction. PsbO expression is markedly reduced in both ΔpirN and ΔnarB. Complementation of NarB or PsbO in ΔpirN largely restores mutant growth and the expression of the other, although to different extents. These findings suggest that PirN is a nitrate-inducible regulator that hierarchically modulates NarB and PsbO expression to couple nitrate assimilation with photosynthetic activity. This coordination likely safeguards redox homeostasis when nitrate assimilation or photosynthetic electron production is perturbed.

INSTRUMENT(S):

ORGANISM(S): Synechocystis Sp. Pcc 6803 Substr. Gt-t

SUBMITTER: Chengcheng Huang

LAB HEAD: Wang Yingchun

PROVIDER: PXD066894 | Pride | 2026-06-08

REPOSITORIES: Pride

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			Action	DRS
	20240516_HCC_2814_1_DIA.raw	Raw
	20240516_HCC_2814_2_DIA.raw	Raw
	20240516_HCC_2814_3_DIA.raw	Raw
	20240516_HCC_WT_1_DIA.raw	Raw
	20240516_HCC_WT_2_DIA.raw	Raw

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Coordination of Cyanobacterial Nitrate Assimilation and Photosynthesis by a Novel PsbO-Interacting Protein PirN.

Huang Chengcheng C Xiao Zhen Z Ge Haitao H Wang Gaojie G Dong Jinghui J Wang Yan Y Yang Hang H Wang Xing X Gao Hui H Wang Zhongshu Z Yang Huanling H Zhang Yuanya Y Huang Xiahe X Xu Wu W Ma Weimin W Yang Wenqiang W Wang Yingchun Y

Advanced science (Weinheim, Baden-Wurttemberg, Germany) 20260320 29

Nitrogen assimilation relies on photosynthetically produced energy and reducing equivalents. Here, we identify a small protein, PsbO-interacting regulator of nitrate assimilation (PirN), as a key coordinator of photosynthesis and nitrate assimilation in Synechocystis sp. PCC 6803 (Synechocystis). PirN specifically accumulates in nitrate-grown cells and interacts with the photosystem II (PSII) subunit PsbO. Deletion of pirN (ΔpirN) under nitrate impairs growth, reduces PSII contents and oxygen ev ...[more]

PMID: 41858255

Similar Datasets

Project description:Unlike all other bacteria, the physiology of cyanobacteria is based on the assimilation of organic matter from inorganic carbon driven by oxygenic photosynthesis. This setting poses special regulatory challenges, particularly in integrating carbon and nitrogen metabolism. Several regulatory factors control the primary nitrogen metabolism, such as the PII protein and proteins interacting with it (PirA, PirC or PipX), or the inactivating factors IF7 and IF17 impacting glutamine synthetase activity. However, regulatory proteins of other enzymes in the nitrogen assimilation pathway have not been described thus far. Here, we show that the 81 amino acids regulatory protein NirP1 in the cyanobacterium Synechocystis sp. PCC 6803 functions as an inhibitor of nitrite reductase, a central enzyme in the assimilation of ammonia from nitrate/nitrite. Ectopic overexpression of the nirP1 gene under standard growth conditions led to a pigmentation phenotype and delayed growth, which was correlated by the excretion of nitrite and dramatic changes in metabolite pools. We show that nitrite excretion occurs in Synechocystis wild type cells upon the shift from high CO2 (HC) to low CO2 (LC) conditions when NirP1 expression becomes activated. The expression of nirP1 is controlled by two transcription factors, NtcA, which binds to a recognition site in a repressive position above the transcription start site (TSS), and an activator, which probably binds to an element 60 to 43 nt upstream of the TSS. Therefore, the joint activity of NtcA and this activator leads to the observed induction of NirP1 under LC conditions, whereas it is repressed by shifts to nitrogen starvation. The data demonstrate that NirP1 plays a crucial role in the coordination of C and N primary metabolism in cyanobacteria by targeting the activity of one of the central enzymes. In natural environments, the excreted nitrite will be utilized by other microorganisms; therefore, NirP1 will ultimately impact the activities and composition of the surrounding microbiome.