Emerging Jasmonate Transporters

Abstract

Jasmonic acid (JA) and methyl jasmonate (MeJA) are highly mobile and, when applied to intact plants, these compounds powerfully modulate gene expression. Moreover, activation of jasmonate-responsive genes usually occurs in tissues distal to the treatments. It therefore comes as no surprise that there are jasmonate transporters; these proteins are only now emerging and their discovery is important for a number of reasons. Firstly, biologically active jasmonates such as jasmonoyl-isoleucine (JA-Ile) are potent regulators that are made in small quantities and that need to be delivered to the correct cellular and subcellular sites. Secondly, jasmonates act to redirect resources from growth to defense. For example, when shoots are wounded, jasmonates help to coordinate the appropriate growth of roots so that organ growth rates are balanced even when a distal part of the plant is damaged. Moreover, some plants (Arabidopsis is an example) produce large quantities of the JA-Ile precursor JA upon wounding. JA and/or its immediate precursor can be transported from cell to cell and even from shoot to root (Gasperini et al., 2015; Figure 1A–1C). The mechanisms underlying this transport need to be identified. However, a difficulty for the jasmonate field is that many studies of JA/JA-Ile transport have used exogenous jasmonates applied at sometimes non-physiological levels to plant tissues. These studies can be difficult to interpret, so the discovery of jasmonate transporter mutants represents a welcome breakthrough. Among these is the newly reported jasmonate transporter (JAT1) from Arabidopsis (Li et al., 2017).