Root hydrotropism is controlled via a cortex-specific growth mechanism ($)

Hydrotropism is the curvature of a plant root towards water. Previous work showed that the hormone abscisic acid (ABA), but not the auxin transporters AUX1 and PIN, is required for hydrotropism, demonstrating that the mechanisms of hydrotropism and gravitropism are distinct. Previous work also showed that MIZU-KUSSEI1 (MIZ1), a gene of unknown function, is required for hytrotropism.  In this new work, Dietrich et al. showed that an ABA-responsive protein kinase is required for hydrotropism, and further, that expression of both SnRK2.2  and MIZ1 in the root cortex is needed for hydrotropism. Furthermore, the root cap and root meristem do not seem to be involved in the perception and response to a water gradient. Nature Plants 10.1038/nplants.2017.57