Comparative mutant analysis of Arabidopsis ABCC-type ABC transporters: AtMRP2 contributes to detoxification, vacuolar organic anion transport and chlorophyll degradation.
The enormous metabolic plasticity of plants allows detoxification of many harmful compounds that are generated during biosynthetic processes or are present as biotic or abiotic toxins in their environment. Derivatives of toxic compounds such as glutathione conjugates are moved into the central vacuole via ATP-binding cassette (ABC)-type transporters of the multidrug resistance-associated protein (MRP) subfamily. The Arabidopsis genome contains 15 AtMRP isogenes, four of which (AtMRP1, 2, 11 and 12) cluster together in one of two major phylogenetic clades. We isolated T-DNA knockout alleles in all four highly homologous AtMRP genes of this clade and subjected them to physiological analysis to assess the function of each AtMRP of this group. None of the single atmrp mutants displayed visible phenotypes under control conditions. In spite of the fact that AtMRP1 and AtMRP2 had been described as efficient ATP-dependent organic anion transporters in heterologous expression experiments, the contribution of three of the AtMRP genes (1, 11 and 12) to detoxification is marginal. Only knockouts in AtMRP2 exhibited a reduced sensitivity towards 1-chloro-2,4-dinitrobenzene, but not towards other herbicides. AtMRP2 but not AtMRP1, 11 and 12 is involved in chlorophyll degradation since ethylene-treated rosettes of atmrp2 showed reduced senescence, and AtMRP2 expression is induced during senescence. This suggests that AtMRP2 is involved in vacuolar transport of chlorophyll catabolites. Vacuolar uptake studies demonstrated that transport of typical MRP substrates was reduced in atmrp2. We conclude that within clade I, only AtMRP2 contributes significantly to overall organic anion pump activity in vivo.
Frelet-Barrand
Annie
A
Zurich Basel Plant Science Center, University of Zurich, Plant Biology, Zollikerstrasse 107, CH-8008 Zürich, Switzerland.
Kolukisaoglu
H Uner
HU
Plaza
Sonia
S
Rüffer
Maika
M
Azevedo
Louis
L
Hörtensteiner
Stefan
S
Marinova
Krasimira
K
Weder
Barbara
B
Schulz
Burkhard
B
Klein
Markus
M
D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D000483:Alleles; D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D002734:Chlorophyll / Q000378:metabolism*; D018548:Cotyledon / Q000235:genetics; D004252:DNA Mutational Analysis; D004269:DNA, Bacterial; D035264:Flowers / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D005959:Glucosidases / Q000378:metabolism; D008658:Inactivation, Metabolic; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics*; D009154:Mutation / Q000235:genetics; D027361:Organic Anion Transporters / Q000378:metabolism*; D018517:Plant Roots / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D018675:Toxicity Tests; D014617:Vacuoles / Q000378:metabolism*
D018528:ATP-Binding Cassette Transporters; D029681:Arabidopsis Proteins; D002734:Chlorophyll; D004269:DNA, Bacterial; D005959:Glucosidases; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D027361:Organic Anion Transporters; C495596:MRP1 protein, Arabidopsis; C495597:MRP2 protein, Arabidopsis; C036483:T-DNA