Affiliation:
1. Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei, China
2. University of Chinese Academy of Sciences, Beijing, China
3. SINOPEC Research Institute of Petroleum Processing, Beijing, China
Abstract
ABSTRACT
Nitrite, a common form of inorganic nitrogen (N), can be used as a nitrogen source through N assimilation. However, high levels of nitrite depress photosynthesis in various organisms. In this study, we investigated which components of the photosynthetic electron transfer chain are targeted by nitrite stress in
Synechocystis
sp. strain PCC 6803 cells. Measurements of whole-chain and photosystem II (PSII)-mediated electron transport activities revealed that high levels of nitrite primarily impair electron flow in PSII. Changes in PSII activity in response to nitrite stress occurred in two distinct phases. During the first phase, which occurred in the first 3 h of nitrite treatment, electron transfer from the primary quinone acceptor (Q
A
) to the secondary quinone acceptor (Q
B
) was retarded, as indicated by chlorophyll (Chl)
a
fluorescence induction, S-state distribution, and Q
A
−
reoxidation tests. In the second phase, which occurred after 6 h of nitrite exposure, the reaction center was inactivated and the donor side of photosystem II was inhibited, as revealed by changes in Chl fluorescence parameters and thermoluminescence and by immunoblot analysis. Our data suggest that nitrite stress is highly damaging to PSII and disrupts PSII activity by a stepwise mechanism in which the acceptor side is the initial target.
IMPORTANCE
In our previous studies, an alga-based technology was proposed to fix the large amounts of nitrite that are released from NO
X
-rich flue gases and proved to be a promising industrial strategy for flue gas NO
X
bioremediation (W. Chen et al., Environ Sci Technol 50:1620–1627, 2016,
https://doi.org/10.1021/acs.est.5b04696
; X. Zhang et al., Environ Sci Technol 48:10497–10504, 2014,
https://doi.org/10.1021/es5013824
). However, the toxic effects of high concentrations of nitrite on algal cells remain obscure. The analysis of growth rates, photochemistry, and protein profiles in our study provides important evidence that the inhibition by nitrite occurs in two phases: in the first phase, electron transfer between Q
A
−
and Q
B
is retarded, whereas in the second, the donor side of PSII is affected. This is an excellent example of investigating the “early” inhibitory effects (i.e., within the first 6 h) on the PSII electron transfer chain
in vivo
. This paper provides novel insights into the mechanisms of nitrite inhibition of photosynthesis in an oxygenic phototrophic cyanobacterium.
Funder
National Program on Key Basic Research Project
State Key Laboratory of Freshwater Ecology and Biotechnology
National Natural Science Foundation of China
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
26 articles.
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