Molecular mechanisms to sense soil overlay and optimize emergence in plants

The famous Mexican proverb says “They tried to bury us, they did not know we were seeds”. Seeds buried under the soil find their way through the soil particles and emerge out. The mechanical pressure of the soil cover induces the production of the gaseous hormone ethylene in plants. Ethylene promotes formation of an apical hook to protect the plant tip when seedlings try to penetrate through the soil. The dark environment under the soil cover also promotes apical hook formation. Once the seedlings reach the soil surface the apical hook opens to expose the meristem and initiate the development of aerial parts. Recent studies suggest the integration of the ethylene and light signaling pathway to regulate soil emergence. Here we summarize our current understanding of how light and ethylene signals coordinate to optimize seedling establishment. This might contribute towards crop improvement programs as successful emergence is critical for survival of seeds plants in natural environments and agricultural fields.