Metilação diferencial do DNA e metabolismo do nitrogênio em variedades de arroz submetidas a alto e baixo suprimento de nitrato

Abstract

Nitrogen (N) is one of the elements most required by plants, and it constitutes the structure of the main macromolecules of the biological systems. In order to increase the grain yield, large amounts are applied in the soil. However, up to 50 to 70% of N applied maybe lost by several processes. To identify biochemistry and molecular mechanisms that might to increase nitrogen use efficiency (NUE) by plants is one of greatest challenges in plant mineral nutrition nowadays. Several molecular techniques have been used in order to study different genotypes related to NUE and to identify potential biotechnological targets for this characterisitic. Lately, it has been noted that aspects related to the control of gene expression, more precise the epigenetic, explains great part of the plant adaptation to stress. This study had as objective to identify the changes of the DNA methylation pattern in four rice varieties with different protein content in the grains, when submitted to high and low nitrate availability conditions. The gene expression of nitrate transporters and the nitrogen metabolites were also evaluated. During the experiment period, the N availability influenced in the DNA methylation pattern, and it showed polymorphism among the rice varieties in the two dosages of nitrate. The rice plants under low nitrogen availability (0.2 mM) showed predominance of the CHG type methylation, whereas when submitted to high availability (2 mM) they showed predominance of CG methylation. The higher expression of high affinity nitrate transporters was observed in the Piauí variety. The Piauí and Manteiga varieties showed an increase in the root shoot ratio, the highest nitrate amount in the sheath and root, the highest amino N, ammonium and total N amount, when submitted to low nitrate availability. The Piauí and Manteiga varieties originated from Maranhão State, where they are grown with low usage of fertilizers by subsistence crop farmers. This way, it is possible that this study results reflect the adaptation of this rice plants to limiting N soil conditions.