Epigenetic marks in an adaptive water stress-responsive gene in tomato roots under normal and drought conditions

RODRIGO M. GONZALEZ; MARTINIANO M. RICARDI; NORBERTO D IUSEM

EPIGENETICS

LANDES BIOSCIENCE

Lugar: Austin, Texas; Año: 2013

1559-2294

Tolerance to water deficit was evolutionarily relevant to the conquest of land by primitive plants. In this context, epigenetic events may have played important roles in the establishment of drought stress responses. We decided to inspect epigenetic marks in the plant organ that is crucial in the sensing of drought stress: the root. Using tomato as a crop model plant, we detected methylated epialleles of Asr2, a protein-coding gene widespread in the plant kingdom supposed to alleviate restricted water availability. We found the three contexts (CG, CNG and CNN) of methylated cytosines in the regulatory region of Solanum lycopersicum Asr2,but only CG in the gene body. To test the hypothesis of a link between epigenetics marks and the adaptation of plants to drought, we explored the cytosine methylation status in root Asr2 resulting from water-deficit stress conditions imposed. We found that a brief exposure to drought-simulated environmental conditions brings about removal of methyl marks in the regulatory region at 77 of the 142 CNN sites. In addition, when studying histone modifications around this model gene in roots, we found that the distal regulatory region was rich in H3K27me3 (typical repressive mark) but its abundance did not change as a consequence of stress. Besides, under normal conditions, both regulatory and coding regions portrayed the H3K9me2 mark, which was lost after 30 minutes of water deprivation. As analogously hypothesized for the paralogous gene Asr1, rapidly acquired new Asr2 epialleles in somatic cells due to desiccation may be stable enough and heritable through the germ line across generations, thus efficiently contributing to constitutive, adaptive gene expression during evolution of desiccation-tolerant populations or species.