Interactions of S-methylmethionine and UV-B can modify the defence mechanisms induced in maize
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We examined the interactions of an exogenously added non-proteinogenic amino acid, S-methylmethionine (SMM) and UV-B radiation in young maize plants. We observed that exposure to UV-B light caused a substantial increase in both the phenolics and anthocyanin contents. Pretreatment with SMM also induced a slight, but statistically significant increase in the total phenol content, and was also able to accelerate the rise in the UV-B-induced anthocyanin level. Gene expression patterns indicated that the general phenylpropanoid pathway was most strongly induced by the combined effect of SMM and UV, while the anthocyanin synthesis by the sole UV-B treatment. SMM treatment and UV-B light led to a substantial increase in the activities of the antioxidant enzymes catalase (CAT), ascorbate peroxidase (APX) and glutathione S-transferase and SMM pretreatment always enhanced the effect of UV-B. While the activity of CAT showed a significant increase in UV-B- and/or SMM-treated plants, APX was stimulated only by SMM. The present results suggest that the protective mechanisms induced by UV-B radiation could be enhanced by SMM treatment and reinforce the earlier observations of priming effects of SMM so that it can contribute to our knowledge about the SMM-induced protection against various types of stressors.
KeywordsAntioxidant enzymes Anthocyanins Maize Phenolics S-methylmethionine UV-B
Cyanidin 3-glucoside equivalents
Untreated plants grown under control light
Plants grown under control light and treated with S-methylmethionine
Variable to maximum chlorophyll fluorescence ratio
Gallic acid equivalents
Photosynthetic photon flux density
Quantitative real-time polymerase chain reaction
Plants irradiated with UV but not treated with S-methylmethionine
Plants irradiated with UV and treated with S-methylmethionine
The authors thank Dr. Demeter Lásztity for all his help and advice, Györgyi Balogh for her technical assistance and Barbara Harasztos for revising the manuscript linguistically. Thanks are due to Csaba Marton (MTA ATK Department of Maize Breeding) for providing the maize seeds. This work was funded by a grant from the Hungarian National Scientific Research Fund (OTKA K108834).
Conflict of interest
The authors declare that they have no conflict of interest.
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