The Role for Jasmonates in Wheat Dormancy Release by Stratification

Hydration at low temperatures, treatment known as stratification, is widely used to break seed dormancy in many species, including wheat. However, the mechanism by which cold regulates dormancy is largely unknown. Our previous studies showed that jasmonic acid (JA) and its derivative methyl jasmonate promote dormancy release in wheat. We have now found that the stratification of dormant grains is correlated with an increase in endogenous JA content in the embryo. Cold triggers JA production rapidly in dormant embryos after transfer from cold (4°C) to room temperature (20°C). The induction of JA production is dependent on the extent of cold imbibition and is tightly linked with initiation of germination. In addition, we have explored the relationship between JA and abscisic acid (ABA), a well-known dormancy promoter, in cold regulation of dormancy. We found an inverse relationship between JA and ABA content in dormant wheat grains that had been imbibed in the cold and transferred to room temperature. Our results indicate that the action of JA on cold-stratified grains is mediated by suppression of two key ABA biosynthesis genes.