Seminars

Morphogenesis at the shoot apex is regulated by the interactions between mechanics and the phytohormone auxin; however, exactly how mechanics regulates auxin is unknown. By using a newly developed software MorphoGraphX and conducting careful quantitative analyses, we have found that two mechanical parameters, turgor pressure and membrane tension, can regulate the auxin efflux carrier PIN1 and auxin accumulation pattern. Osmotic treatment, external force application, and membrane tension modulation comprehensively suggest that PIN1 protein level and intracellular localization (including its polar distribution) are sensitive to mechanical alterations, especially to changes in membrane tension. Membrane tension can act as a sensor of tissue mechanics through cell wall strain and directly influence vesicle trafficking at the cellular level. One implication of this fundamental mechanism is robust growth promotion in young primordia: the mechanical changes associated with growth facilitate auxin accumulation and drive further growth.