Putrescine treatment has a higher effect on 5mC DNA methylation profile of wheat leaves under white than under blue light conditions

Polyamines play a pivotal role in plant growth and development by modulating metabolite levels and even regulating DNA methylation. To reveal novel insights into the intricate relationship among polyamines, metabolites and DNA methylation, the impact of exogenous putrescine on wheat was investigated at several levels. Since the outcome of putrescine treatment may vary depending on the light quality, the experiment was performed under both white and blue light. Metabolite profiling revealed distinct changes induced by blue light and/or putrescine. Blue light alone had increasing effects on several metabolites, but the effect of putrescine was dominant under blue light in most cases. Putrescine had a decreasing effect on some amino acids and the γ-glutamyl-cycle, while increasing effect on the TCA-cycle. Distinct changes in DNA methylation patterns were detected in response to blue light, putrescine or their combination. Blue light exerted strong effects on methylation, and putrescine application slightly could induce further changes. Putrescine had a higher impact under white as increased the leaf spermidine level, and parallel with this, a lower level of up-methylated genes involved in cellular processes, but a higher level of down-methylated genes involved in molecular function and biological processes occurred compared to the blue light. MeDIP DNA sequencing on the population of winter wheat (Triticum aestivum L. variety ‘Mv Béres’) grown on modified Hoagland solution in growth chambers under 16/8-h light/dark periodicity and 22/20 °C day/night temperature with and 75% relative humidity [26], and under two different light spectrums. Under white (W) light, 32.32% blue, 45.71% green, 20.71% red and 1.25% far-red composition, while under blue (B) light, 82.14% blue, 1% green, 16.7% red and 0.17% far-red composition was applied at 250 µmol m-2 s−1 photosynthetic photon flux density. Seven days after the germination, half of the plants grown under either W or B light conditions were further grown without any treatment (WC or BC), while the other part of them got 0.5 mM PUT supplementation in the hydroponic solution (WP or BP) in the next 7 days.