A regulation for seed germination based on the physical separation of enzyme and substrate

Enhancing seed germination is a key objective of central importance to food security and for world economy. The lack of molecular understanding of seed germination, represents a fundamental gap in our ability to enhance food security across a period of rapid growing population and climate change. In this study, leads by Dr. Raquel Iglesias-Fernández, the contribution of genes encoding endo-β-mannanases (MAN) to seed germination of Brassica rapa (oilseed rape) and its close relative Sisymbrium officinale has been stablished. Transcripts of the most abundant MAN genes (MAN2, MAN5, MAN6 y MAN7) upon seed germination of these species are mainly located to micropylar endosperm in S. officinale seeds and to the radicle tip in the B. rapa embryo; however mannans have been localized to the imbibed external seed coat layer (mucilage) in both species. This apparent discrepancy, where substrate and its hydrolytic enzyme are physically separated, suggest a movement of MAN enzymes, that are synthesized with typical signal peptides, from the embryo tissues to the mucilage layer (via apoplastic space) is necessary for the mannans to be hydrolyzed.