A touchy subject: Ca signaling during leaf movements in Mimosa.

Mimosa pudica, the sensitive plant, responds to stimuli such as touch and wounding with leaf movements that propagate throughout the plant. The motion is driven by changes in the turgor of specialized cells in a set of motor organs called pulvinae. By imaging cellular Ca levels as the wave of movement propagates through the leaf, Hagihara and colleagues now show that Ca signals precede and predict the pulvinar movements. These results provide compelling support for a model where Mimosa uses a Ca-related response system to trigger its leaf movements. These researchers then used CRISPR to delete a critical genetic regulator of pulvinar development, producing plants with immobile leaves. These plants experienced more herbivory than wild type, suggesting that the Ca-triggered leaf movements are an adaptation to deter herbivory.