ABSTRACT
Nitrate, the major nitrogen source for most plants, is widely used as a fertilizer and as a result has become a predominant freshwater pollutant. Plants need nitrate for growth and store most of it in the central vacuole. Some members of the chloride channel (CLC) protein family, such as the torpedo-fish ClC-0 and mammalian ClC-1, are anion channels, whereas the bacterial ClC-ec1 and mammalian ClC-4 and ClC-5 have recently been characterized as Cl-/H+ exchangers with unknown cellular functions. Plant members of the CLC family are proposed to be anion channels involved in nitrate homeostasis; however, direct evidence for anion transport mediated by a plant CLC is still lacking. Here we show that Arabidopsis thaliana CLCa (AtCLCa) is localized to an intracellular membrane, the tonoplast of the plant vacuole, which is amenable to electrophysiological studies, and we provide direct evidence for its anion transport ability. We demonstrate that AtCLCa is able to accumulate specifically nitrate in the vacuole and behaves as a NO3-/H+ exchanger. For the first time, to our knowledge, the transport activity of a plant CLC is revealed, the antiporter mechanism of a CLC protein is investigated in a native membrane system, and this property is directly connected with its physiological role.
Subject(s)
Arabidopsis Proteins/metabolism , Arabidopsis/cytology , Arabidopsis/metabolism , Chloride Channels/metabolism , Nitrates/metabolism , Vacuoles/metabolism , Arabidopsis/genetics , Arabidopsis Proteins/genetics , Chloride Channels/deficiency , Chloride Channels/genetics , Electric Conductivity , Ion Transport , Proton Pumps/deficiency , Proton Pumps/genetics , Proton Pumps/metabolism , ProtonsABSTRACT
Factor Analysis can extract salient features from EEG data and reduce redundancy of multi-channel computerized EEG data. A 16-channel computerized frequency analysis of background brain electrical activity during 3 functional conditions (eyes closed, eyes open and hyperventilation) was carried out in two groups, fifty healthy subjects and twenty-three schizophrenics. The power log-transformed relative values of normal subjects and schizophrenic patients were submitted to Factor Analysis and the resulting factor scores were compared. Schizophrenics showed EEG abnormalities in delta 2, theta 1 and alpha 2 bands for the first factor, accounting for the eyes closed condition, and in theta 2 and beta 2 bands for the second factor, accounting for the eyes open condition. This preliminary study demonstrates the utility of Factor Analysis in managing and comparing computerized EEG data.