| This thesis studies the hormonal control of seed dormancy and germination by examining the action of two plant hormones, gibberellins (GA) and abscisic acid (ABA). This work also aims to transfer known Arabidopsis hormone signaling data into hexaploid bread wheat. The purpose of this transfer is to gain greater understanding of these hormone's actions on seed dormancy and germination. This thesis work extends our understanding of GA signal transduction through the cloning and characterization of SLEEPY1 ( SLY1) and the exploration of genetic interactions with its homologue SNEEZY (SNE). SLY1 and SNE both encode F-box proteins, which are subunits of SCF E3 ubiquitin ligase complexes. SLY1 and SNE affect the disappearance of RGA protein, a negative regulator of GA signal transduction, indicating that RGA is the target of SCFSLY1 and possibly SCFSNE. Characterization of the genetic interaction between SLY1 and SNE reveals that the recessive-interfering mutations in SLY1 are rescued by overexpression of SNE. In further studies, ABA signal transduction mutants were identified in wheat, which will allow for the dissection of commonalities in signaling between the model system Arabidopsis and a hexaploid crop plant. Both wheat ABA-insensitive and ABA-hypersensitive mutants were isolated in germination screens, with some secondary phenotypes examined. |
