Different low-nitrogen-stress regimes result in distinct DNA-methylation patterns, metabolic profiles, and morpho-physiological changes in rice

Aims DNA methylation and demethylation are epigenetic responses to abiotic stresses. The aims of this study were to i) identify alterations in the DNA methylation patterns among rice plants grown with sufficient and low nitrogen (N) levels; ii) observe whether conditioning to N stress promoted alterations in methylation patterns; and iii) search for possible relationships among methylation alterations and phenotypic, physiological, and metabolic changes. Methods The N-stress treatments applied were as follows: over three consecutive generations, plants were either exposed to sufficient N (60 kg N ha(-1) - Control group) or N stress (10 kg N ha(-1) ) for only the last generation (NS1), the first and third generations (NS2 - intermittent stress), or all three generations (NS3 - recurrent stress). Non-stress cycles received sufficient N. Results It was observed that N stress led to a reduction in total DNA methylation compared to control. The greatest reduction was observed in the hemi-methylated bands. NS1- and NS3-treated plants had similar reductions in the total hemi-methylated and fully-methylated bands, as well as similar phenotypic characteristics and photosynthetic efficiencies. On the other hand, the NS2 treatment increased the number of fully-methylated bands, which corresponded with a strong reduction in grain yield and photosynthetic efficiency. Conclusion It was found that N stress stimulates changes in DNA methylation and that the duration of N-stress conditioning interferes with the methylation patterns of plants. Finally, a strong relationship between methylation status and photosynthetic, agronomic and N-use parameters was found.

Automated summary

The study revealed that nitrogen stress induces changes in DNA methylation, with the duration of stress conditioning affecting the methylation patterns of plants. Moreover, a strong correlation between methylation status and photosynthetic, agronomic, and nitrogen-use parameters was observed.