Mitochondria provide the main source of cytosolic ATP for activation of outward-rectifying K+ channels in mesophyll protoplast of chlorophyll-deficient mutant rice (OsCHLH) seedlings.
The role of mitochondria in providing intracellular ATP that controls the activity of plasma membrane outward-rectifying K+ channels was evaluated. The OsCHLH rice mutant, which lacks chlorophyll in the thylakoids, was isolated by T-DNA gene trapping (Jung, K.-H., Hur, J., Ryu, C.-H., Choi, Y., Chung, Y.-Y., Miyao, A., Hirochika, H., and An, G. (2003) Plant Cell Physiol. 44, 463-472). The OsCHLH mutant is unable to fix CO2 and exhibits reduced growth. Wild type and mutant plants exhibit similar rates of respiratory O2 uptake in the dark, whereas the rate of photosynthetic O2 evolution by the mutant was negligible during illumination. During dark respiration the wild type and mutant exhibited similar levels of cytoplasmic ATP. In the mutant oligomycin treatment (an inhibitor of mitochondrial F1F0-ATPase) drastically reduced ATP production. The fact that this was reversed by the addition of glucose suggested that the mutant produced ATP exclusively from mitochondria but not from chloroplasts. In whole cell patch clamp experiments, the activity of outward-rectifying K+ channels of rice mesophyll cells showed ATP-dependent currents, which were 1.5-fold greater in wild type than in mutant cells. Channels in both wild type and mutant cells were deactivated by the removal of cytosolic ATP, whereas in the presence of ATP the channels remained active. We conclude that mesophyll cells in the OsCHLH rice mutant derive ATP from mitochondrial respiration, and that this is critical for the normal function of plasma membrane outward-rectifying K+ channels.
Goh
Chang-Hyo
CH
Bionanotechnology Center, Department of Life Science, Pohang University of Science and Technology, Kyungbuk, Korea. gohunse@postech.ac.kr
Jung
Ki-Hong
KH
Roberts
Stephen K
SK
McAinsh
Martin R
MR
Hetherington
Alistair M
AM
Park
Youn-il
YI
Suh
KyeHong
K
An
Gynheung
G
Nam
Hong Gil
HG
D000255:Adenosine Triphosphate / Q000737:chemistry*; D002245:Carbon Dioxide / Q000737:chemistry; D002462:Cell Membrane / Q000378:metabolism; D002734:Chlorophyll / Q000737:chemistry / Q000235:genetics*; D003600:Cytosol / Q000378:metabolism*; D005838:Genotype; D005947:Glucose / Q000378:metabolism; D006720:Homozygote; D008027:Light; D008564:Membrane Potentials; D008928:Mitochondria / Q000378:metabolism*; D008957:Models, Genetic; D009154:Mutation; D012275:Oryza / Q000235:genetics*; D010100:Oxygen / Q000378:metabolism; D010101:Oxygen Consumption; D018408:Patch-Clamp Techniques; D010641:Phenotype; D010788:Photosynthesis; D016133:Polymerase Chain Reaction; D011188:Potassium / Q000737:chemistry; D015221:Potassium Channels / Q000737:chemistry*; D024683:Potassium Channels, Tandem Pore Domain; D011523:Protoplasts / Q000378:metabolism; D013997:Time Factors
D015221:Potassium Channels; D024683:Potassium Channels, Tandem Pore Domain; D002734:Chlorophyll; D002245:Carbon Dioxide; D000255:Adenosine Triphosphate; D005947:Glucose; D011188:Potassium; D010100:Oxygen