Molecular physiological analysis of the two plastidic ATP/ADP transporters from Arabidopsis.
Arabidopsis (Arabidopsis thaliana) possesses two isoforms of plastidic ATP/ADP transporters (AtNTT1 and AtNTT2) exhibiting similar biochemical properties. To analyze the function of both isoforms on the molecular level, we examined the expression pattern of both genes by northern-blot analysis and promoter-beta-glucuronidase fusions. AtNTT1 represents a sugar-induced gene mainly expressed in stem and roots, whereas AtNTT2 is expressed in several Arabidopsis tissues with highest accumulation in developing roots and young cotyledons. Developing lipid-storing seeds hardly contained AtNTT1 or -2 transcripts. The absence of a functional AtNTT1 gene affected plant development only slightly, whereas AtNTT2T-DNA, AtNTT1-2T-DNA, and RNA interference (RNAi) plants showed retarded plant development, mainly characterized by a reduced ability to generate primary roots and a delayed chlorophyll accumulation in seedlings. Electron microscopic examination of chloroplast substructure also revealed an impaired formation of thylakoids in RNAi seedlings. Moreover, RNAi- and AtNTT1-2T-DNA plants showed reduced accumulation of the nuclear-encoded protein CP24 during deetiolation. Under short-day conditions reduced plastidic ATP import capacity correlates with a substantially reduced plant growth rate. This effect is absent under long-day conditions, strikingly indicating that nocturnal ATP import into chloroplasts is important. Plastidic ATP/ADP transport activity exerts significant control on lipid synthesis in developing Arabidopsis seeds. In total we made the surprising observation that plastidic ATP/ADP transport activity is not required to pass through the complete plant life cycle. However, plastidic ATP/ADP-transporter activity is required for both an undisturbed development of young tissues and a controlled cellular metabolism in mature leaves.
Reiser
Jens
J
Pflanzenphysiologie, Fachbereich Biologie, Universität Kaiserslautern, D-67663 Kaiserslautern, Germany.
Linka
Nicole
N
Lemke
Lilia
L
Jeblick
Wolfgang
W
Neuhaus
H Ekkehard
HE
D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D005838:Genotype; D018525:Germination / Q000235:genetics / Q000502:physiology; D050356:Lipid Metabolism; D000226:Mitochondrial ADP, ATP Translocases / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D010641:Phenotype; D018515:Plant Leaves / Q000254:growth & development / Q000378:metabolism; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism; D030821:Plants, Genetically Modified; D018087:Plastids / Q000378:metabolism*; D036226:Seedlings / Q000235:genetics / Q000254:growth & development / Q000648:ultrastructure; D012639:Seeds / Q000235:genetics / Q000254:growth & development
D000226:Mitochondrial ADP, ATP Translocases