IDENTIFICATION OF 3 GENETIC-LOCI CONTROLLING LEAF SENESCENCE IN ARABIDOPSIS-THALIANA

Four mutants that show the delayed leaf senescence phenotype were isol ated from Arabidopsis thaliana. Genetic analyses revealed that they ar e all monogenic recessive mutations and fall into three complementatio n groups, identifying three genetic loci controlling leaf senescence i ii Arabidopsis. Mutations in these loci cause delay in all senescence parameters examined, including chlorophyll content, photochemical effi ciency of photosystem tl, relative amount of the large subunit of Rubi sco, and RNase and peroxidase activity. Delay of the senescence sympto ms was observed during both age-dependent in planta senescence and dar k-induced artificial senescence in all of the mutant plants. The resul ts indicate that the three genes defined by the mutations are key gene tic elements controlling functional leaf senescence and provide decisi ve genetic evidence that leaf senescence is a genetically programmed p henomenon controlled by several monogenic loci in Arabidopsis. The res ults further suggest that the three genes function at a common step of age-dependent and dark-induced senescence processes. It is further sh own that one of the mutations is allelic to ein2-1, an ethylene-insens itive mutation, confirming the role of ethylene signal transduction pa thway in leaf senescence of Arabidopsis.