Sex as a response to oxidative stress: a twofold increase in cellular reactive oxygen species activates sex genes.
Organisms are constantly subjected to factors that can alter the cellular redox balance and result in the formation of a series of highly reactive molecules known as reactive oxygen species (ROS). As ROS can be damaging to biological structures, cells evolved a series of mechanisms (e.g. cell-cycle arrest, programmed cell death) to respond to high levels of ROS (i.e. oxidative stress). Recently, we presented evidence that in a facultatively sexual lineage--the multicellular green alga Volvox carteri--sex is an additional response to increased levels of stress, and probably ROS and DNA damage. Here we show that, in V. carteri, (i) sex is triggered by an approximately twofold increase in the level of cellular ROS (induced either by the natural sex-inducing stress, namely heat, or by blocking the mitochondrial electron transport chain with antimycin A), and (ii) ROS are responsible for the activation of sex genes. As most types of stress result in the overproduction of ROS, we believe that our findings will prove to extend to other facultatively sexual lineages, which could be indicative of the ancestral role of sex as an adaptive response to stress and ROS-induced DNA damage.
Department of Biology, University of New Brunswick, Fredericton, Canada. anedelcu@unb.ca
Aurora M
AM
Nedelcu
Oana
O
Marcu
Richard E
RE
Michod
D020418:Algal Proteins / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D000968:Antimycin A; D020224:Expressed Sequence Tags; D005786:Gene Expression Regulation / Q000235:genetics*; D006023:Glycoproteins / Q000235:genetics* / Q000378:metabolism; D006358:Hot Temperature; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D018384:Oxidative Stress / Q000502:physiology*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D012723:Sex; D013050:Spectrometry, Fluorescence; D044446:Volvox / Q000378:metabolism / Q000502:physiology*
D020418:Algal Proteins; D006023:Glycoproteins; D017382:Reactive Oxygen Species; D000968:Antimycin A