Transport mechanisms of plant hormones

Plant growth, development, and response to the environment are mediated by a group of small signaling molecules named hormones. Plants regulate hormone response pathways at multiple levels, including biosynthesis, metabolism, perception, and signaling. In addition, plants exhibit the unique ability to spatially control hormone distribution. In recent years, multiple transporters have been identified for most of the plant hor-mones. Here we present an updated snapshot of the known transporters for the hormones abscisic acid, auxin, brassi-nosteroid, cytokinin, ethylene, gibberellin, jasmonic acid, sali-cylic acid, and strigolactone. We also describe new findings regarding hormone movement and elaborate on hormone substrate specificity and possible genetic redundancy in hor-mone transport and distribution. Finally, we discuss subcellu-lar, cell-to-cell, and long-distance hormone movement and local hormone sinks that trigger or prevent hormone-mediated responses.