Constitutive expression of JASMONATE RESISTANT 1 elevates content of several jasmonates and primes Arabidopsis thaliana to better withstand drought

ABSTRACT Jasmonates have a well-documented role in balancing the trade-off between plant growth and defense against biotic stresses. However, the role of jasmonate signaling under abiotic stress is less well studied. Here, we investigated the function of JASMONATE RESISTANT 1 (JAR1) in drought stress in Arabidopsis thaliana. JAR1 converts jasmonic acid (JA) to jasmonyl-L-isoleucine (JA-Ile), the major bioactive form of jasmonates. Comparison of a newly generated over-expression line (JAR1-OE) with jar1-11, a T-DNA insertion line in the JAR1 locus, and Col-0 revealed that constitutively increased JA-Ile production results in stunted growth and a delay in flowering. Upon water limitation, JAR1-OE plants retained more water in their leaves, showed reduced wilting and recovered better from drought stress than the wild type. By contrast, jar1-11 mutant plants were hypersensitive to drought. RNA-seq analysis and hormonal profiling of plants under control and drought stress conditions provided insight into the molecular reprogramming caused by the alteration in JA-Ile content. Especially JAR1-OE plants were affected in many adaptive systems related to drought stress, including stomatal density, stomatal aperture or the formation of reactive oxygen species (ROS). Overall, our data suggest that constitutively increased expression of JAR1 can prime Arabidopsis towards improved drought tolerance. One sentence summary Constitutive expression of JAR1primes Arabidopsis thaliana to better withstand drought stress