Researchers from Japan have discovered a new, yet simple, way to increase drought tolerance in a wide range of plants. Published in Nature Plants, the study reports a newly discovered biological pathway that is activated in times of drought. By working out the details of this pathway, scientists were able to induce greater tolerance for drought-like conditions simply by growing plants in vinegar.
The large collaborative effort began with the discovery of novel Arabidopsis mutants that have strong drought tolerance. These plants have a mutation to an enzyme called HDA6 (histone deacetylase6), and the first goal of the current study was to determine exactly how this mutation allows the plants to grow normally without water.
Initial testing in normal Аrabidopsis under drought stress showed that expression of hda6 was linked to activation of the biological pathway that produces acetate, the main component of vinegar. In the mutated plants, they found that under the same conditions, this pathway was activated even more, and plants produced larger amounts of acetate. Further analysis showed that activity of the HDA6 enzyme acts as a switch that controls which type of metabolic pathway is active. Normally plants break down sugar for energy, but in time of drought, they switch to the acetate-producing pathway to stimulate the jasmonate (JA (plant hormone)) signalling pathway to confer drought tolerance.
The team next measured acetate levels in normal plants and found that the amount of acetate produced by plants during drought directly correlated to how well they survived. These results predicted that increasing the amount of acetate in plants could help them survive drought. The team tested this hypothesis by treatment of normal plants with acetic acid, other organic acids, or water before drought stress. They found that after 14 days without water over 70% of the plants treated with acetic acid had survived, while virtually all other plants had died. In addition exogenous acetic acid promotes de novo JA synthesis.
The scientists mapped the entire signaling pathway from the HDA6 switch, and realized that this pathway is highly conserved across different plant species. Furthermore, the external application of acetic acid successfully enhanced the drought tolerance in Arabidopsis, rapeseed, maize, rice and wheat plants, when the plants were grown in optimal acetic acid concentrations.
Their findings highlight a radically new survival strategy that exploits an epigenetic switch of metabolic flux conversion and hormone signalling by which plants adapt to drought.