Reactive carbonyl species metabolism in glycophyte Arabidopsis thaliana and its close relative extreme halophyte Schrenkiella parvula under salt stress

This study investigates the contrasting abilities of the glycophyte Arabidopsis thaliana and the halophyte Schrenkiella parvula to manage reactive carbonyl species (RCS) under salt stress. The results reveal distinct patterns of RCS accumulation and enzymatic activity, and identify a distinct carbonyl profile in the halophyte. A. thaliana exhibited significant RCS accumulation and oxidative stress, whereas S. parvula maintained a distinct and more tightly regulated RCS profile, with lower accumulation of key cytotoxic carbonyls such as acrolein, indicating a difference in the composition of the constitutive carbonyl pool rather than uniformly lower carbonyl content. Physiological analyses showed that increasing NaCl concentrations caused a dramatic decline in the Fv/Fm ratio of A. thaliana , indicating impaired photosynthesis, whereas S. parvula sustained stable Fv/Fm values under high salinity. Under salinity, the two species differed in how RCS-detoxifying enzymes were regulated rather than in a uniform increase: glutathione-S-transferase (GST) was the enzyme most consistently up-regulated in S. parvula (up to twofold), whereas aldehyde dehydrogenase (ALDH) and aldo–keto reductase (AKR) showed treatment-dependent changes in both species. Exogenous RCS treatments revealed species-specific detoxification efficiencies. S. parvula displayed a strong increase in ALDH and AKR activity, particularly under high acrolein concentrations, whereas A. thaliana did not sustain comparable induction at elevated RCS levels. The strong induction of GST in S. parvula indicates a pronounced capacity to activate these activities upon direct RCS exposure. The study also examined the hormonal responses of both species to RCS exposure. In A. thaliana , abscisic acid (ABA) and salicylic acid (SA) levels increased in response to HNE and HHE, while acrolein reduced ABA levels. In contrast, S. parvula exhibited a more stable hormonal profile. Hormones were measured only after exogenous RCS application and not under the NaCl series, so these responses relate only indirectly to salt tolerance. Notably, S. parvula showed a pronounced increase in jasmonic acid (JA) after RCS exposure, which may contribute to its stress response, although a causal role remains to be established. Overall, these findings characterize carbonyl metabolism in a halophyte and identify glutathione conjugation as a candidate pathway for functional investigation; application to crop improvement is a perspective requiring genetic and physiological validation rather than a conclusion of this work.