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Mitochondrial response to oxidative stress is intricately related to cellular homeostasis due to the high susceptibility of the mitochondrial genome to oxidative damage. Octocoral mitogenomes possess a unique DNA repair gene, mtMutS, potentially capable of counteracting the effects of oxidative stress induced mtDNA damage. Despite this unique feature, the response of octocoral mitochondria to increased oxidative stress remains unexplored. Here we explore the response of the octocoral Sinularia cf. cruciata to elevated temperature and low-pH stress and its ability to reverse acute oxidative mtDNA damage caused by exogenous agents like hydrogen peroxide (H2O2). The differential transcriptional response to these climate change-related stresses was recorded for two mtDNA-encoded genes and three stress biomarkers. Only HSP70 was significantly upregulated during thermal stress whereas significant reduction in the expression levels of HSP70, GPX, and COI was observed along with an increased number of mtMutS transcripts during low-pH stress. Damage to mtDNA was evident, accompanied by changes in mtDNA copy number. Damage caused by H2O2 toxicity was reversed within 5 hours and initial mtDNA copy number apparently influenced damage reversal. Our results indicate that different stress-specific resilience strategies are used by this octocoral species and its mitochondria to reverse oxidative stress and associated mtDNA damage. These experiments provide the first account on the response of octocoral mitochondria with its unique gene repertoire among animals to different stressors and highlight its potential role in conferring resilience to the host cells during different climate change scenarios.
This is a submission to PeerJ for review.
mtDNA damage and repair in other octocorals species
Quantification of mtDNA lesion frequency (MLF) per 10 kb DNA by SLR-qPCR amplification of total DNA from Sinulariasp. and Briareumsp. exposed to 5 mM H2O2 for 30 min (designated as ‘Treatment’) followed by recovery for 1h (designated as ‘Rec-1H’). Data represents the mean ± s.e.m. of three replicates.