Abstract
Thiamin and thiamin pyrophosphate (TPP) are well known for their important roles in human nutrition and enzyme catalysis. In this work, we present new evidence for an additional role of these compounds in the protection of cells against oxidative damage. Arabidopsis (Arabidopsis thaliana) plants subjected to abiotic stress conditions, such as high light, cold, osmotic, salinity, and oxidative treatments, accumulated thiamin and TPP. Moreover, the accumulation of these compounds in plants subjected to oxidative stress was accompanied by enhanced expression of transcripts encoding thiamin biosynthetic enzymes. When supplemented with exogenous thiamin, wild-type plants displayed enhanced tolerance to oxidative stress induced by paraquat. Thiamin application was also found to protect the reactive oxygen species-sensitive ascorbate peroxidase1 mutant from oxidative stress. Thiamin-induced tolerance to oxidative stress was accompanied by decreased production of reactive oxygen species in plants, as evidenced from decreased protein carbonylation and hydrogen peroxide accumulation. Because thiamin could protect the salicylic acid induction-deficient1 mutant against oxidative stress, thiamin-induced oxidative protection is likely independent of salicylic acid signaling or accumulation. Taken together, our studies suggest that thiamin and TPP function as important stress-response molecules that alleviate oxidative stress during different abiotic stress conditions.
Highlights
Thiamin and thiamin pyrophosphate (TPP) are well known for their important roles in human nutrition and enzyme catalysis
The results of these analyses showed that relative to control plants, the total thiamin content was significantly increased in Arabidopsis seedlings subjected to cold, osmotic, and salinity conditions as well as the application of the superoxide radical-generating compound paraquat (Fig. 1A)
Because oxidative damage is one of the major outcomes associated with cold, salt, and paraquat treatments (Hernandez et al, 1993; Prassad et al, 1994; Durmusand Kadioglu, 2005; Bogdanovicet al., 2008), we narrowed the focus of our investigation to study the relationship between thiamin biosynthesis and oxidative stress induced via paraquat
Summary
Thiamin and thiamin pyrophosphate (TPP) are well known for their important roles in human nutrition and enzyme catalysis. Arabidopsis (Arabidopsis thaliana) plants subjected to abiotic stress conditions, such as high light, cold, osmotic, salinity, and oxidative treatments, accumulated thiamin and TPP. Thiamin-induced tolerance to oxidative stress was accompanied by decreased production of reactive oxygen species in plants, as evidenced from decreased protein carbonylation and hydrogen peroxide accumulation. Our studies suggest that thiamin and TPP function as important stress-response molecules that alleviate oxidative stress during different abiotic stress conditions. In addition to thiamin’s well-known role in human nutrition and as an enzyme cofactor; recent studies suggested that thiamin could function to alleviate stress in different organisms. Observations supporting this role for thiamin have been reported in bacteria, fungi, animals, and plants. Genetic and metabolic evidence for a direct role of thiamin in alleviating abiotic stress in plants was not, to the best of our knowledge, presented so far
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