| Light, acting both through photosynthesis and through a series of specific morphogenic photoreceptors, regulates nearly every stage of whole plant growth and development. Several major classes of photoreceptors have been isolated and well characterized, such as phytochromes, cryptochromes and phototropins (Cashmore et al., 1999; Quail, 2002a, b). By characterizing mutants from these photoreceptors, the functions of the individual photoreceptors and of intermediate components in the signal transduction pathways initiated by these photoreceptors have been gradually clarified. (Quail, 1991; Short and Briggs, 1994; Smith, 1995; Fankhauser and Chory, 1997; Quail, 2002a).; In order to study phyA-induced pathways, we initiated a screen to look for genetic mutants with lower anthocyanin accumulation, a commonly used phenotype for studying phyA-stimulated transduction chains. As a result, four mutants were identified and designated lid (light-d&barbelow;eficient). Two of these mutants, lid1 and lid2, are the primary subject illustrated in this dissertation. These mutants exhibit reduced some, but not all, phyA-induced mutant phenotypes. These results indicate that both lid1 and lid2 maybe novel genetic mutants in the phyA signaling pathway, and that both LID1 and LID2 may encode proteins not yet implicated in light responses. The genetic, physiological and biochemical characterizations of both lid1 and lid2 may help in elucidating light-mediated responses. |
