THE DEAD, MATERNALLY DERIVED ORGANS ENCLOSING EMBRYOS FUNCTION AS LONG TERM STORAGE FOR ACTIVE PROTEINS AND NUTRIENTS WHICH SUPPORT SEEDLING ESTABLISHMENT
Raviv, B., James, G., Granot, G., Gutterman, Y. and Grafi, G.
French Associates Institute of Agriculture and Biotechnology of Drylands, The Institutes for Desert Research, Ben-Gurion University of the Negev, Midreshet Ben-Gurion, 84990, Israel
Contact: Buzi Raviv, Buziraviv@gmail.com
In angiosperms, the embryo is dispersed from the mother plants surrounded by remnants of the mother reproductive organs such as indehiscent fruits and seed coats. For instance, in dicots, the integument layers will form the seed coats; in wild grasses, the dispersal units consist of the caryopsis surrounded by the dead floral bracts. The maternally derived organs (MDO) of grasses are undesired in agriculture but their adaptive value has not been fully explored. We investigated the proposal that the MDO of seeds and dispersal units have been evolved to function more than just means for physical embryo protection. We showed that dead floral bracts of Wild Emmer Wheat (Triticum turgidum var dicoccoides) store and release upon hydration active hydrolases including nucleases and chitinases, which maintain activity years after the mother plant dies. Proteome and ICP analysis revealed multiple oxidative and pathogenesis stress related proteins and nutrients that are released upon hydration. Further analysis showed that although germination from the intact dispersal unit of wild emmer wheat was delayed, post germination growth was better than that of separated caryopses. In some of the studied dicot species, seed coats and pericarps exhibited microbial growth control activity of the seed coat extracts, even after years of storage in uncontrolled conditions. Thus, our study show that the dead, MDO enclosing the embryo store active hydrolases and other substances that can engineer the micro environment of the germinating seed; support seed persistence in the soil, serve as a first line of defense during germination and increase seedling establishment.