The small peptide XT-6 promotes seed germination in tobacco

Seed germination is a critical developmental transition tightly controlled by interdependent molecular networks, yet the role of endogenous peptides in this process remains poorly understood. Here, by integrating transcriptomic and peptidomic analyses of germinating tobacco seeds, we identify a previously uncharacterized signalling peptide, Xiaotai 6 (XT-6), as a positive regulator of seed germination. Exogenous application of XT-6 significantly enhanced germination rates in a concentration-dependent manner, with maximal efficacy at 0.5-1 μM, whereas CRISPR/Cas9-generated xt-6 mutants exhibited delayed and reduced germination. Multi-omics analyses revealed that XT-6 functions as a serine protease inhibitor that globally attenuates translation efficiency. This modulation fine-tunes the brassinosteroid biosynthesis pathway and alters the stability of key germination-related transcription factors, thereby promoting the transition from dormancy to germination. Our findings uncover peptide-mediated translational control as a previously overlooked layer of regulation in seed germination and offer novel strategies for improving seedling establishment in crops.