Journal of Tropical Oceanography ›› 2022, Vol. 41 ›› Issue (2): 159-169.doi: 10.11978/2021040CSTR: 32234.14.2021040

• Marine Biology • Previous Articles     Next Articles

Effects of salinity on the growth and transcriptome of euryhaline Synechococcus sp. K1*

LIAO Ying1,2(), XIA Xiaomin1,2()   

  1. 1. Key Laboratory of Tropical Marine Bio-resources and Ecology (South China Sea Institute of Oceanology, Chinese Academy of Sciences), Guangzhou 510301, China
    2. University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2021-04-06 Revised:2021-05-01 Online:2022-03-10 Published:2021-05-03
  • Contact: XIA Xiaomin E-mail:liaoying18@mails.ucas.ac.cn;xiaxiaomin@scsio.ac.cn
  • Supported by:
    Nature Science Foundation of China(41906131);Key Deployment Program of Center for Ocean Mega-Science, Chinese Academy of Sciences(COMS2020Q09);Guangdong Basic and Applied Basic Research Foundation(2019A1515011340)

Abstract:

Synechococcus, which is one of the representative groups of picocyanobacteria, is widely distributed in global oceans and estuaries. It has high phenotypic (pigment) and genetic diversity. According to the level of ability to deal with variation in salinity, Synechococcus can be divided into the strictly marine type and euryhaline type. In this study, we compared the growth of Synechococcus sp. K1 (isolated from the Pearl River estuary) and Synechococcus sp. YX02-1 (isolated from the South China Sea oligotrophic water) under a series of salinity gradient conditions. We also conducted phylogenetic analysis of K1 and YX02-1 based on rpoC1 gene sequences. We found that euryhaline Synechococcus sp. K1 could grow in all salinity levels, while strictly marine Synechococcus sp. YX02-1 was unable to survive below 13‰, which is consistent with the distribution characteristics in the estuary. Transcriptome analysis showed that the expression of genes (ggpS, SPS, stpA) that synthesize osmotic pressure regulator molecules in euryhaline Synechococcus were significantly down-regulated, while the gene expression of the membrane channel protein glzT was significantly up-regulated under low-salinity condition. This suggests that the low-salt tolerance mechanism of euryhaline Synechococcus mainly includes reducing the synthesis of small molecules related to intracellular osmotic pressure and increasing membrane channel proteins to improve the efflux of small molecules. In addition, salinity affected the photosynthesis and metabolism levels of euryhaline Synechococcus. The expression of photosynthesis energy-saving genes (ATPF0B, ATPF0A, ATPF1D, ATPF1A) and pigment protein genes (cpcA, cpcB) were significantly down-regulated under low-salinity condition, and the expression of inorganic nitrogen utilization-related genes were up-regulated. Under low-salinity condition, the demand for small molecules related to osmotic pressure is reduced, which can make more carbon sources to support growth. Meanwhile, the absorption of inorganic nitrogen is enhanced. These two reasons may be responsible for the higher growth of Synechococcus under low-salinity condition.

Key words: Euryhaline Synechococcus, transcriptome analysis, salinity

CLC Number: 

  • P735.121