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MEPS prepress abstract   -  DOI: https://doi.org/10.3354/meps13263

Inducible versus constitutive antioxidant defenses along an environmental stress gradient

Kathryn L. Van Alstyne*, Lauren Sutton, Sue-Ann Gifford

*Corresponding author:

ABSTRACT: Optimal defense theory (ODT) predicts that antiherbivore defenses should be constitutive when plants are frequently attacked and inducible when the probability of attack is low. Like antiherbivore defenses, antioxidant defenses can be inducible or constitutive. We hypothesized the ODT predictions should apply to antioxidant defenses; thus, species inhabiting environments where oxidative stresses occur frequently should produce constitutive antioxidant defenses, whereas species in environments where stresses occur less frequently should produce inducible defenses. We tested this hypothesis by attempting to induce production of the antioxidant dimethylsulfoniopropionate (DMSP) in four ulvoid algae that experience different levels of environmental stress because they are zoned along a tidal gradient. The two lower intertidal species Ulvaria obscura and Ulva fenestrata, which experience oxidative stresses less frequently, induced DMSP production in response to applications of the chemical oxidant hydrogen peroxide within 7 days, whereas the higher intertidal species Ulva linza and Ulva intestinalis, which regularly experience oxidative stress, did not. This study demonstrates a novel waterborne signaling mechanism for DMSP induction in marine macroalgae and provides evidence of selection for producing inducible antioxidant defenses in organisms experiencing frequent environmental stresses.