Plant Physiol, May 2000, Vol. 123, pp. 345-352
Regulation of Carbonic Anhydrase Expression by Zinc, Cobalt, and
Carbon Dioxide in the Marine Diatom Thalassiosira
weissflogii1
Todd W.
Lane* and
François M.M.
Morel
Department of Geosciences, Guyot Hall, Princeton University,
Princeton, New Jersey 08544-1003
TWCA1 is the major Zn-requiring isoform of carbonic anhydrase (CA)
in the marine diatom Thalassiosira weissflogii. We have examined the roles that trace metals and CO2 play in the
regulation of TWCA1 expression over ranges of concentrations that
bracket those encountered in the marine environment. Both steady-state levels of TWCA1 and the kinetics of induction were measured by western
analysis. TWCA1 levels correlated well with cellular CA activity
levels. TWCA1 was induced at a low CO2 concentration but
the level of induction, as determined by western analysis, was
dependent on the availability of Zn. Co effectively substituted for Zn
in regulating TWCA1 expression and promoting TWCA1 activity. Upon shift
from low to high CO2, the concentration of TWCA1 decreased. The expression of TWCA1 is diel cycle regulated, and cellular TWCA1
decreased during the dark phase. These results provide the basis for
studying the expression of CA in field populations and, taken together
with previous radiolabeling studies, provide strong evidence of in vivo
metal substitution of Co for Zn in a CA. Our data also support the
conclusion that TWCA1 plays a central role in carbon acquisition in
T. weissflogii.
1
This work was supported by grants from the
National Science Foundation and by the Center for Environmental
Bioinorganic Chemistry.
*
Corresponding author; e-mail tlane{at}princeton.edu; fax 609-
258-1274.
© 2000 American Society of Plant Physiologists
