Title : Dead pericarps function as storage for active hydrolases and germination inhibitory substances
Abstract:
Fruits can be divided into two classes; dry fruits and fleshy fruits. Dry fruits, in which the coat (pericarp) undergoes death and hardening at maturity categorized as either dehiscent, whereby the dry fruit is opened at maturity to allow seed dispersal or indehiscent, whereby the dry fruit does not open at maturity and act as a dispersal unit. The pericarp enclosing the seed is believed to provide a major physical shield against harmful environmental conditions as well as assisting in seed dispersal. A recent study in our lab demonstrated that the maternally-derived dead organs enclosing the embryo (seed coat) in Brassicaceae and Fabaceae species as well as hardened floral bracts of wheat dispersal units (e.g., glumes) store and release upon hydration hydrolytic enzymes and other growth regulatory substances that might assist seed germination and seedling establishment. We wanted to address if similar function is carried out by dead pericarps. We focused on Sinapis alba (white mustard) because the fruit is composed of dehiscent and indehiscent parts, and investigated the potential of the dead pericarps to store active proteins and nutrients and their potential to support or inhibit seed germination.
Preliminary proteome analysis revealed that S. alba pericarps released upon hydration multiple proteins including stress related proteins, hydrolases and extracellular proteins. In gel nuclease assays of proteins released from S. alba dehiscent and indehiscent pericarps showed the both pericarps possess active nucleases. This appears to be a general phenomenon in plants in as much as the dead pericarps of other plant species including Arabidopsis thaliana, Coriandrum sativum L (Apiaceae), Spartium junceum L (Fabaceae) and Trigonela arabica Delile (Fabaceae) store and release upon hydration active nucleases. Elemental analysis revealed the abundant accumulation of major and minor nutrients in the S. alba pericarp and surprisingly there is more accumulation of nutrients in indehiscent pericarp compared dehiscent pericarp. Preliminary germination experiments showed that substances released from the pericarps inhibited seed germination of S. alba. Thus, our results explored previously unknown features of the pericarp serving as a reservoir of substances that might play an important role in seed germination and seedling establishment.
I am studying a unique, previously unexplored field in plant sciences - the role of dead organs enclosing embryos (seed coats, pericarps, glumes etc.) in long term preservation of active proteins and nutrients and their role in seed persistence and germination. This study would interest the audience in the conference and help me gain ideas for future research directions
