High intracellular phosphorus contents exhibit a correlation with arsenate resistance in chlamydomonas mutants.
Pi in the medium relieved the toxicity of arsenate against cellular growth of Chlamydomonas reinhardtii. To investigate the relationship between intracellular P contents and arsenate resistance, we determined the intracellular P contents of arsenate-sensitive and arsenate-resistant mutants, which had been generated by random insertional mutagenesis. All 13 arsenate-resistant mutants showed higher P contents than the parent strain, while arsenate-sensitive mutants with high P contents were not found. In one of the arsenate-resistant mutants, AR3, the intracellular P content was about twice that in the wild type during growth in the absence of arsenate. Arsenate incorporation in AR3 was suppressed within 10 min after the addition of 1 mM arsenate, while Pi incorporation continued even after arsenate uptake ceased. Whereas the P content of the wild type decreased to half in the presence of 0.5 mM arsenate, almost the same degree (about 50%) of decrease was observed in AR3 cells grown in the presence of as much as 3 mM arsenate. AR3, in which PTB1, a homolog of a Pi transporter gene, had been disrupted, exhibited a higher activity of a high-affinity Pi transporter, suggesting that it may be due to a compensatory transport activity. These data suggest that the intracellular level of P is one of the important factors of arsenate resistance.
Kobayashi
Isao
I
School of Life Science, Tokyo University of Pharmacy and Life Science, Horinouchi, Hachioji, Tokyo, 192-0392 Japan.
Fujiwara
Shoko
S
Shimogawara
Kosuke
K
Sakuma
Chiseko
C
Shida
Yasuo
Y
Kaise
Toshikazu
T
Usuda
Hideaki
H
Tsuzuki
Mikio
M
D000818:Animals; D001149:Arsenates / Q000378:metabolism / Q000633:toxicity*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D016825:Chlamydomonas reinhardtii / Q000187:drug effects* / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance / Q000502:physiology*; D007424:Intracellular Fluid / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010758:Phosphorus / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
D001149:Arsenates; D002352:Carrier Proteins; D010758:Phosphorus; C025657:arsenic acid