Genetic, Physiological And Molecular Characterizaton Of A Developmentally Retarded Mutant (drml) In Arabidopsis Thaliana

In a screening for stay-green mutants in Arabidopsis, a developmentally retarded mutant, drm1, was obtained from ethyl methanesulfonate (EMS) -mutagenized M2 seeds in Columbia (Col-0) genetic background. Genetic analysis showed that the drml carries a single, recessive nuclear mutation. The mutation was mapped to the bottom of chromosome 5 and located within a region of 80 kb between markers AtMXK3 . 2 and AtF1505. 1.The drml mutation causes a pleiotropic phenotype, including small and thick cotyledons, increased numbers of cauline and rosette (curling and pale green) leaves, increased branches, reduced apical dominance, and increased inflorescences with infertile siliques and / or seeds and abnormal numbers of petals (3-5) and stamens (3~5). In addition, the drml mutation also results in many developmental defects, including reduced seed germination rate (86.2%), delayed seed germination process (7d), slow growth rate of primary root, cotyledons and leaves, prolonged vegetative growth, delayed flowering time (88d), and prolonged lifespan (157d).To determine the roles of DRM1 in growth and development, a few characteristic traits related to growth and development were investigated physiologically and molecularly in the drml mutant, including flowering time, sugar metabolism and/or signaling, hormone homeostasis and signaling, and cell cycle.The drml mutant flowered late under all photoperiod conditions, and its late flowering phenotype was significantly restored by vernalization treatment. Moreover, the transcript levels of FLC as well as EMF and TFL1 genes were significantly up-regulated in the drml. These results suggest that the drml is involved in the regulation of the autonomous flowering pathway, and that DRM1 functions as a repressor of the flowering-related genes FLC, EMF and TFL1.The DRM1 mutation resulted in an increase in the levels of sucrose, chlorophyll and anthocyanin. An altered response to sucrose and glucose was also observed in the drml mutant, which resulted in the increased transcript levels of several sucrose-responsive genes. The drml mutant...