Elucidating the molecular mechanism of the inhibitory effect
of epigallocatechin-3-gallate on Microcystis aeruginosa
Received: 5 August 2017 / Revised and accepted: 7 December 2017 /Published online: 11 May 2018
Springer Science+Business Media B.V., part of Springer Nature 2017
Epigallocatechin-3-gallate (EGCG), an eco-friendly polyphenol, has a strong inhibitory effect on the bloom-forming cyanobacte-
rium Microcystis aeruginosa. In order to reveal the molecular mechanism of algal inhibition of plant polyphenols, quantitative
proteome analysis based on iTRAQ (isobaric tags for relative and absolute quantification) was applied to investigate EGCG-
induced proteomic changes in M. aeruginosa. Following treatment with EGCG for 48 h, the total protein content was compared
with that of untreated cells, and 88 differentially expressed proteins were identified, of which 30 were upregulated and 58 were
downregulated. Proteins involved in chlorophyll biosynthesis, carbon and nitrate assimilation and cell division were among the
most downregulated, which resulted in growth suppression. By contrast, anti-oxidative proteins and molecular chaperones, such as
superoxide dismutase, glutaredoxin, and heat shock proteins, were distinctly upregulated. Eighteen potentially crucial proteins were
selected for assessment of transcription by real-time quantitative PCR, which confirmed the results of proteomic experiment. In
addition, immunoblotting confirmed downregulation of three representative proteins, magnesium-protoporphyrin IX monomethyl
ester [oxidative] cyclase AcsF, glutamine synthetase GlnN, and metalloprotease FtsH, following EGCG treatment, consistent with
the results of iTRAQ quantitation experiment. It is speculated that chlorophyll biosynthesis, carbon and nitrate assimilation, and cell
division are the main inhibition targets of EGCG.
In recent decades, frequent outbreaks of cyanobacterial blooms
in China have caused great harm to ecosystems and human
health. Members of the Microcystis genus of cyanobacteria
are the dominant cause of algal blooms in lakes related to the
Yangtze river, which form periodically and can last a long time
(Chen et al. 2003; Tan et al. 2009). Controlling the recruitment
andgrowthofMicrocystis is crucial for preventing such
blooms, and biological methods are potentially highly efficient,
economically attractive, and eco-friendly. Allelochemicals in
waste plant tissues are considered as promising low-cost algi-
cides (Ball et al. 2001;LiandHu2005;Parketal.2006). Based
on previous research, we tested a variety of readily available
plant materials for treating Microcystis aeruginosa and found
that tea extract displayed the highest algal inhibition activity.
Following this, epigallocatechin-3-gallate (EGCG) was isolated
from tea extract and found to be the active ingredient (Lu et al.
2013). EGCG is a major water-soluble component and the most
abundant polyphenolic compound (60%), accounting for 7.3–
14.3% of the gross weight of dry green tea (Zhao et al. 2008).
The inhibitory mechanism of plant polyphenols on
cyanobacteria is not completely understood and may involve
interaction with proteins, inhibition of alkaline phosphatase,
interruption of the electron transfer process, or oxidant dam-
age (Spencer et al. 1988; Gross et al. 1996, 2003; Dziga et al.
2007; Zhu et al. 2010). The activities of superoxide dismutase
and catalase were enhanced under oxidant stress (Hong et al.
2009;Shaoetal.2009), and Shao et al. (2009)reportedthat
levels of psbA, recA, grpE, prx,andfabZ were altered
Jin Wang and Chen Dai contributed equally to this work and are
considered as co-first authors.
Electronic supplementary material The online version of this article
(https://doi.org/10.1007/s10811-017-1370-5) contains supplementary
material, which is available to authorized users.
* Yaping Lu
Experimental Teaching Center of Biology, College of Life Sciences,
Nanjing Agricultural University, Nanjing 210095, China
State Key Laboratory of Lake Science and Environment, Nanjing
Institute of Geography and Limnology, Chinese Academy of
Sciences, Nanjing 210008, China
Journal of Applied Phycology (2018) 30:1747–1758