CHARACTERIZATION OF A PHOSPHATE-ACCUMULATOR MUTANT OF ARABIDOPSIS-THALIANA

We have characterized a novel mutation of Arabidopsis thaliana at a lo cus designated pho2. pho2 mutants accumulated up to 3-fold more total P in leaves, mostly as inorganic phosphate (Pi), than wild-type seedli ngs. In addition, we isolated a mutant (locus designated pho1-2, an al lelle of pho1-1 described by Y. Poirier, S. Thoma, C. Somerville, J. S chiefelbein [1991] Plant Physiol 97: 1087-1093) with low Pi concentrat ions in leaves. When grown under high transpiration conditions, leaves of pho2 seedlings became severely P intoxicated, whereas shoots of ph o1-2 mutants were P deficient and wild-type seedlings were normal. A p ho1/pho2 double mutant resulting from a cross between the single mutan ts was identified in the F-2 generation and shown to have a pho1 pheno type. Prior to the development of P toxicity symptoms, P was the only mineral nutrient whose concentration was greater in pho2 mutants than wildtype seedlings. Compared to wild-type, pho2 mutants had greater Pi concentrations in stems, siliques, and seeds, but roots of pho2 mutan ts had similar or lower Pi concentrations than either pho1 mutants or wild-type seedlings. We suggest that the pho2 mutation affects a funct ion normally involved in regulating the concentration of Pi in shoots of Arabidopsis.