Relative stability of ploidy in a marine Synechococcus across various growth conditions.

Blanca Perez‐Sepulveda,Andrew Millard,Laurence Garczarek,Frances Pitt,Morgane Ratin,David J Scanlan,An N N'Guyen

doi:10.1111/1758-2229.12614

Abstract

Marine picocyanobacteria of the genus Synechococcus are ubiquitous phototrophs in oceanic systems. Consistent with these organisms occupying vast tracts of the nutrient impoverished ocean, most marine Synechococcus so far studied are monoploid, i.e., contain a single chromosome copy. The exception is the oligoploid strain Synechococcus sp. WH7803, which on average possesses around 4 chromosome copies. Here, we set out to understand the role of resource availability (through nutrient deplete growth) and physical stressors (UV, exposure to low and high temperature) in regulating ploidy level in this strain. Using qPCR to assay ploidy status we demonstrate the relative stability of chromosome copy number in Synechococcus sp. WH7803. Such robustness in maintaining an oligoploid status even under nutrient and physical stress is indicative of a fundamental role, perhaps facilitating recombination of damaged DNA regions as a result of prolonged exposure to oxidative stress, or allowing added flexibility in gene expression via possessing multiple alleles.

Highlights

SummaryMarine picocyanobacteria of the genus Synechococcus are ubiquitous phototrophs in oceanic systems
Low nutrient concentration across vast tracts of the world’s oceans has meant that organisms have to compete for scarce resources (Raven, 1998)
WH7803 during growth is similar to that observed in the oligoploid freshwater cyanobacterium Synechococcus elongatus PCC 7942 (Griese et al, 2011), which shows an increase in ploidy at the end of the lag phase (Watanabe et al, 2015)

Summary

Marine picocyanobacteria of the genus Synechococcus are ubiquitous phototrophs in oceanic systems. Consistent with these organisms occupying vast tracts of the nutrient impoverished ocean, most marine Synechococcus so far studied are monoploid, i.e., contain a single chromosome copy. We set out to understand the role of resource availability (through nutrient deplete growth) and physical stressors (UV, exposure to low and high temperature) in regulating ploidy level in this strain. Such robustness in maintaining an oligoploid status even under nutrient and physical stress is indicative of a fundamental role, perhaps facilitating recombination of damaged DNA regions as a result of prolonged exposure to oxidative stress, or allowing added flexibility in gene expression via possessing multiple alleles

Introduction

Results and discussion

Conclusions