Figure 1.

AtJAT3 and AtJAT4 interactions in driving long distance leaf-to-leaf translocation of JA. (a) Y2H analysis of interactions between AtJAT3 and AtJAT3, AtJAT4 and AtJAT4, and AtJAT3 and AtJAT4. The yeast strain NMY51 was co-transformed with bait construct Cub-AtJAT3/4 or Cub-AtJAT1, and prey construct Nub-AtJAT3/4. The transformants were grown on synthetic SD without Leu and Trp (SD-LW) plate or synthetic SD without Leu, Trp and His and Ade (SD-LWHA). (b) Confocal microscopy analysis of BiFC in Nicotiana benthamiana epidermal leaf cells revealed physical interactions between AtJAT3 and AtJAT3, AtJAT4 and AtJAT4, and AtJAT3 and AtJAT4, while no AtJAT1-AtJAT4 interaction was observed. Scale bar, 25 μm. (c) A model showing that cell-cell transport drives long-distance transmission of JA along the phloem in WSR. Cellular import of wound-induced JA (indicated by white cycles) from apoplast by AtJAT3-AtJAT3 and AtJAT4-AtJAT4 homodimers and AtJAT3-AtJAT4 heterodimer, as well as export of JA to apoplast by exporter(s) such as AtJAT1 is essential to mediate cell-cell transport along the phloem. Furthermore, de novo biosynthesis of JA (indicated by orange cycles) by positive feedback enables self-propagation of JA during cell-cell transport, generating JA waves to trigger systemic immunity in distal leaves. The local damaged leaves (leaf 7, 8 and 9 indicated) and systemic leaves (the parastichy leaf 12, 13 and 14) are indicated by black lines and orange stars respectively