Role of Spermidine in Overwintering of Cyanobacteria

Abstract

Polyamines are found in all groups of cyanobacteria, but their role in environmental adaptation has been barely investigated. In Synechocystis sp. strain PCC 6803, inactivation of spermidine synthesis genes significantly reduced the survivability under chill (5°C)-light stress, and the survivability could be restored by addition of spermidine. To analyze the effects of spermidine on gene expression at 5°C, lacZ was expressed from the promoter of carboxy(nor)spermidine decarboxylase gene (CASDC) in Synechocystis. Synechocystis 6803::P CASDC -lacZ pretreated at 15°C showed a high level of LacZ activity for a long period of time at 5°C; without the pretreatment or with protein synthesis inhibited at 5°C, the enzyme activity gradually decreased. In a spermidine-minus mutant harboring P CASDC -lacZ, lacZ showed an expression pattern as if protein synthesis were inhibited at 5°C, even though the stability of its mRNA increased. Four other genes, including rpoA that encodes the ␣ subunit of RNA polymerase, showed similar expression patterns. The chill-light stress led to a rapid increase of protein carbonylation in Synechocystis. The protein carbonylation then quickly returned to the background level in the wild type but continued to slowly increase in the spermidine-minus mutant. Our results indicate that spermidine promotes gene expression and replacement of damaged proteins in cyanobacteria under the chill-light stress in winter. IMPORTANCEOutbreak of cyanobacterial blooms in freshwater lakes is a worldwide environmental problem. In the annual cycle of bloomforming cyanobacteria, overwintering is the least understood stage. Survival of Synechocystis sp. strain PCC 6803 under longterm chill (5°C)-light stress has been established as a model for molecular studies on overwintering of cyanobacteria. Here, we show that spermidine, the most common polyamine in cyanobacteria, promotes the survivability of Synechocystis under longterm chill-light stress and that the physiological function is based on its effects on gene expression and recovery from protein damage. This is the first report on the role of polyamines in survival of overwintering cyanobacteria. We also analyzed spermidine synthesis pathways in cyanobacteria on the basis of bioinformatic and experimental data.

Microbial survival strategies in ancient permafrost: insights from metagenomics

“…Here we highlight polyamine synthesis genes (spermidine, putricine and cadaverine). These stress-related molecules maintain RNA secondary structure ( Igarashi and Kashiwagi, 2000 ; Takahashi and Kakehi, 2010 ) and are implicated in response to cold ( Zhu et al , 2015 ), low pH ( Carper et al , 1991 ; Schneider et al , 2013 ; Zhu et al , 2015 ), oxidative stress ( Tkachenko et al , 2001 ), membrane integrity and biofilm formation ( Carper et al , 1991 ; Schneider et al , 2013 ; Zhu et al , 2015 ). The high abundance of these genes may also be responsible for the putrefied smell of Pleistocene permafrost.…”

Reporting Key Features in Cold-Adapted Bacteria

“…PAMC 21119, putrescine synthesis was also found to be upregulated while heme protein synthesis was downregulated [ 20 ]. Putrescine and spermidine have been implicated in oxidative and cold stress responses [ 50 , 51 ].…”

Redox crisis underlies conditional light–dark lethality in cyanobacterial mutants that lack the circadian regulator, RpaA

“…S2). Correspondingly, ornithine, which is a known precursor for polyamines (32), was one-third less abundant in ΔrpaA, suggesting mobilization of carbon toward polyamines. Accumulation of polyamines is a known general stress response in cyanobacteria (33), and the observed differences indicate that ΔrpaA cells may be stressed even before they enter the dark.…”