9318055 Foley The goal of this project is to elucidate the physiological basis for seed dormancy and afterripening-induced breaking of dormancy. The aim of this project is to investigate the molecular basis for dormancy/breaking dormancy using complementary molecular and genetic approaches. Research on seed dormancy has been approached mainly by studying breaking of dormancy which complicates interpretation by confounding breaking of dormancy with germination. The molecular and genetic approaches described herein are distinct in that they focus primarily on maintenance of dormancy. The hypothesis to be tested states that specific genes or their products which are expressed in dormant embryos maintain seed in the dormant state. The expression of these genes is repressed during afterripening of dormant embryos which facilitates subsequent germination. Using in vivo and in vitro translation procedures, about 10 polypeptides have been identified that occur in dormant but not afterripened embryos soon after imbibition. A dormancy-specific recombinant library has been developed and sixteen putative dormancy-specific positive clones, whose expression is modulated by afterripening, have been selected. These clones will be further characterized as to their general expression and nucleic acid sequence. To complement this approach it is proposed that molecular markers be identified for major genes associated with the dormancy trait and simultaneously evaluate/refine the tentative genetic model explaining dormancy in A. fatua. In addition, to confirm any genetic modelbased on F2 populations derived for bulk segregant analysis and to better understand the inheritance of dormancy it is proposed that advanced-generation, F2-derived lines that vary in their degree of dormancy be developed and genetically evaluated. This molecular and genetic approach should provide significant information toward understanding the physiological basis for this arrested stage of plant development. ***
