Poster: Oxidative stress

Abs # 95: Does DMSP contribute to stress tolerance in Spartina alterniflora?

Presenter:	Husband, Joseph D, DTheuri@aol.com
Authors	Husband, Joseph D (A) (B)  Kiene, Ronald P (A) (B)
Affiliations:	(A): University South Alabama (B): Dauphin Island Sea Lab

What enables S. alterniflora to thrive in stressful intertidal environments? One characteristic that sets S. alterniflora apart from other marsh macrophytes is its synthesis of dimethylsulfoniopropionate (DMSP). It has been hypothesized that DMSP functions as an antioxidant in marine algae. We propose a similar function in S. alterniflora. Because most environmental stresses appear to be manifested as oxidative stress, the ability of S. alterniflora to produce DMSP may confer advantages to this species. Measurements of DMSP, its oxidation product dimethylsulfoxide (DMSO), and foliar release of dimethylsulfide (DMS) have been measured seasonally, in naturally stressed vs. healthy leaves, and for paraquat treated vs. control leaves. Our findings indicate that DMSP is higher in healthy green leaves (vs.chlorotic leaves). This pattern is reversed for the DMSP degradation product DMSO, which is higher in chlorotic leaves. DMS release is also higher in chlorotic leaves, indicating DMSP degradation. We have also found that the concentration of DMSO and foliar release of DMS is higher in S. alterniflora leaves exposed to paraquat relative to control leaves. This increase in the turnover and oxidation of the cellular DMSP pool in parallel with increased oxidative stress, as indicated by decreased maximum quantum yield of photosystem II and increased activity of antioxidant enzymes, provides compelling evidence for a role of DMSP in oxidative stress protection in S. alterniflora. We will be investigating DMSP dynamics in response to nutrient limitation, exposure to heavy metals, and exposure to UV light (all of which are known to contribute to oxidative stress) in future experiments. Experiments with isolated protoplast and chloroplast suspensions are currently underway as well.