Green leaf volatile sensory calcium transduction in Arabidopsis

Plants perceive volatile organic compounds (VOCs) released by mechanically- or herbivore-damaged neighboring plants and induce various defense responses. Such interplant communication protects plants from environmental threats. However, the spatiotemporal dynamics of VOC sensory transduction in plants remain largely unknown. Using a wide-field real-time imaging method, we visualize an increase in cytosolic Ca(2+) concentration ([Ca(2+)](cyt)) in Arabidopsis leaves following exposure to VOCs emitted by injured plants. We identify two green leaf volatiles (GLVs), (Z)-3-hexenal (Z-3-HAL) and (E)-2-hexenal (E-2-HAL), which increase [Ca(2+)](cyt) in Arabidopsis. These volatiles trigger the expression of biotic and abiotic stress-responsive genes in a Ca(2+)-dependent manner. Tissue-specific high-resolution Ca(2+) imaging and stomatal mutant analysis reveal that [Ca(2+)](cyt) increases instantly in guard cells and subsequently in mesophyll cells upon Z-3-HAL exposure. These results suggest that GLVs in the atmosphere are rapidly taken up by the inner tissues via stomata, leading to [Ca(2+)](cyt) increases and subsequent defense responses in Arabidopsis leaves.