| The early senescent cotyledon (esc1) mutant of Arabidopsis thaliana displays premature senescence of its cotyledons in an acropetal pattern, short stature, a "bushy" rosette, and small, epinastic true leaves. The soluble sugars sucrose, glucose and fructose have variable ameliorative effects on the morphological and early senescence phenotypes of esc1 . Mature rosette leaves exude decreased sucrose and increased glucose and fructose levels; they contain elevated cell wall and vacuolar invertase activities. Microarray data reveal significant changes in pathogen- and stress-response genes, and in carbohydrate hydrolases and transferases. Genetic analysis indicates the esc1 phenotype is due to two recessive mutations. Genetic linkage of the early senescence phenotype to the bottom arm of chromosome one has been established. A model is presented in which lesions in candidate genes involved in invertase regulation, cell wall chemistry, and/or pathogen response interact to produce the mutant phenotype. |
