Drought and sugar transport: From turgor sensing to carbon allocation.
Drought triggers reprogramming of sugar transport, which acts as a central hub linking stress perception to carbon allocation. Under drought, FERONIA acts as a cell wall-plasma membrane turgor sensor that activates SnRK2s via outside-in signaling, and stress-activated kinases (SnRK2s, CPKs, and CIPKs) directly phosphorylate SWEET, SUT1, and TST transporters to enhance long-distance sucrose transport and vacuolar sugar accumulation. Recent cross-species single-cell atlases have identified phloem foundational genes as new targets for improving sugar transport. Meanwhile, deep mutational scanning enables high-throughput screening for SWEETs with enhanced sucrose transport activity. Remaining challenges include the need for characterization of sugar unloading in sink tissues. Thus, sugar transport integrates drought perception with metabolic adjustment, providing principles for engineering carbon partitioning under drought.