Transcriptomic survey on the microcystins production and growth of Microcystis aeruginosa under nitrogen starvation

Yanping Zhou; Xuan Li; Qiongqiong Xia; Ruihua Dai

doi:10.1016/j.scitotenv.2019.134501

Transcriptomic survey on the microcystins production and growth of Microcystis aeruginosa under nitrogen starvation

Sci Total Environ. 2020 Jan 15:700:134501. doi: 10.1016/j.scitotenv.2019.134501. Epub 2019 Nov 2.

Authors

Yanping Zhou¹, Xuan Li¹, Qiongqiong Xia², Ruihua Dai³

Affiliations

¹ Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China.
² North China Municipal Engineering Design & Research Institute Co. Ltd., Tianjin 300074, China.
³ Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China. Electronic address: rhdai@fudan.edu.cn.

PMID: 31689655
DOI: 10.1016/j.scitotenv.2019.134501

Abstract

Cyanobacteria are a vital component of freshwater phytoplankton, and many species are recognized for their ability to produce toxins and harmful algal blooms (HABs). Nitrogen is an essential element of all the complex macromolecules in algal cells. However, the underlying molecular mechanism of the changes in transcriptomic patterns and physiological responses in response to N starvation is poorly understood. The transcriptomes were generated via RNA-sequencing (RNA-Seq) technology to study the major metabolic pathway under N starvation. The results shed light on the mechanism of toxin production and physiological adaptations in Microcystis aeruginosa (M. aeruginosa). The cell density gradually increased during the first two days then declined over time and was finally stable at (15.50 ± 0.5) × 10⁵ cell mL^-1 after 6 days. The chlorophyll-a content and phycocyanin content of M. aeruginosa increased during the first two days and subsequently decreased markedly over time under N starvation. The variable to maximum chlorophyll fluorescence ratio (F_v/F_m ratio) decreased with time under N starvation. Most photosynthesis genes have similarity decreasing trends with growth physiological changes. The microcystins (MCs) levels generally increased first, reaching a peak value with 1.35 pg cell^-1 on the fifth day, and then remained roughly constant. The genes involved in N metabolism-related gene expression were upregulated to maintain normal biological activity, while the genes involved in photosynthesis-related gene expression were downregulated to save energy. All genes encoding algae toxin synthesis were upregulated under N starvation. The observed expression patterns demonstrate that all MCs genes respond similarly to MCs production within the cell. Our results indicate the response mechanism of M. aeruginosa under N starvation and provide a comprehensive understanding of N-controlling cyanobacteria and MCs synthesis.

Keywords: Microcystins; Microcystis aeruginosa; Nitrogen starvation; Physiological responses; Sequence.

MeSH terms

Cyanobacteria
Harmful Algal Bloom
Microcystins / metabolism*
Microcystis / physiology*
Nitrogen / metabolism*
Transcriptome

Substances

Microcystins
Nitrogen