title: Vacuolar Ca2+/H+ transport activity is required for systemic phosphate homeostasis involving shoot-to-root signaling in Arabidopsis.
abstract: Calcium ions (Ca(2+)) and Ca(2+)-related proteins mediate a wide array of downstream processes involved in plant responses to abiotic stresses. In Arabidopsis (Arabidopsis thaliana), disruption of the vacuolar Ca(2+)/H(+) transporters CAX1 and CAX3 causes notable alterations in the shoot ionome, including phosphate (P(i)) content. In this study, we showed that the cax1/cax3 double mutant displays an elevated P(i) level in shoots as a result of increased P(i) uptake in a miR399/PHO2-independent signaling pathway. Microarray analysis of the cax1/cax3 mutant suggests the regulatory function of CAX1 and CAX3 in suppressing the expression of a subset of shoot P(i) starvation-responsive genes, including genes encoding the PHT1;4 P(i) transporter and two SPX domain-containing proteins, SPX1 and SPX3. Moreover, although the expression of several PHT1 genes and PHT1;1/2/3 proteins is not up-regulated in the root of cax1/cax3, results from reciprocal grafting experiments indicate that the cax1/cax3 scion is responsible for high P(i) accumulation in grafted plants and that the pht1;1 rootstock is sufficient to moderately repress such P(i) accumulation. Based on these findings, we propose that CAX1 and CAX3 mediate a shoot-derived signal that modulates the activity of the root P(i) transporter system, likely in part via posttranslational regulation of PHT1;1 P(i) transporters.
authors.affiliation: Agricultural Biotechnology Research Center, Academia Sinica, Taipei 115, Taiwan.
authors.forename: Tzu-Yin
authors.initials: TY
authors.lastname: Liu
authors.forename: Kyaw
authors.initials: K
authors.lastname: Aung
authors.forename: Ching-Ying
authors.initials: CY
authors.lastname: Tseng
authors.forename: Tzu-Yun
authors.initials: TY
authors.lastname: Chang
authors.forename: Ying-Shin
authors.initials: YS
authors.lastname: Chen
authors.forename: Tzyy-Jen
authors.initials: TJ
authors.lastname: Chiou
mesh_terms: D017920:Antiporters / Q000378:metabolism*; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000494:pharmacology; D027682:Cation Transport Proteins / Q000378:metabolism*; D017343:Genes, Plant / Q000235:genetics; D006706:Homeostasis / Q000187:drug effects; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism* / Q000494:pharmacology; D018517:Plant Roots / Q000378:metabolism*; D018520:Plant Shoots / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D013489:Suppression, Genetic / Q000187:drug effects; D014617:Vacuoles / Q000187:drug effects / Q000378:metabolism*
chemical_list: D017920:Antiporters; D029681:Arabidopsis Proteins; C506406:CAX3 protein, Arabidopsis; D027682:Cation Transport Proteins; D009687:Nuclear Proteins; D010710:Phosphates; C000597306:SPX1 protein, Arabidopsis; C027614:calcium-hydrogen antiporters; D002118:Calcium