Global warming and projections of higher drought frequency, coupled with greater urban, recreational, and environmental demands on water resources, has increased our need to understand how plants respond to their hydraulic environment. Epigenetic regulation has recently emerged as an additional layer of regulation acting at the interface between the genotype and the environment, creating phenotypes sensitive to environmental inputs. While much is understood about epigenetic regulation in Arabidopsis, little of that knowledge has been translated to other plant species. The overall goal of this project was to look at epigenetic regulation of known water-related genes and to determine whether water stress induced epigenetic alterations occur for these genes in tomato. Specifically, we used the recently completed tomato genome sequence to identify genes that both have transposons close to the transcription start site and are known to be sensitive to changes in water availability. Solanum lycopersicum cv. Heinz 1706 plants were subjected to high and low water treatments. Plant growth, water-use, carbon isotope ratio, and plant water potential were monitored. Regulation (up or down) of known drought-related genes in tomato were compared between high and low water treatments and correlated with potential epigenetic regulation.
Results/Conclusions
High water treatment plants had significantly greater plant biomass (36.9 g dry weight vs. 9.94 g) compared with low water treatment plants. Mid-day water potentials averaged -0.94 MPa for the high water treatment compared with -1.69 MPa for the low water treatment just prior to harvest. Over a six day period, pot water loss averaged 598.7 g/day for high water treatment plants compared with just 82.4 g/day for the low water treatment. These differences were all significant at P<0.0001. The number of tomato fruits produced did not differ significantly between the two treatments, however high water treatment plants averaged fruit weights of 42.2 g compared with just 11.7 g for the low water treatment plants. Planting of seeds collected from both high and low treatment plants indicated a difference in germination rates. Seeds harvested from tomato plants from the high water treatment averaged a 96 % germination rate compared with just 66.7 % for the low treatment plants. This study has confirmed physiological differences between the two treatments for both growth and water-related traits. In addition, this study has confirmed differences in the regulation of drought-related genes and has correlated this with potential epigenetic regulation.