Plant Physiol, February 2003, Vol. 131, pp. 595-602
Zinc Efficiency Is Correlated with Enhanced Expression and
Activity of Zinc-Requiring Enzymes in Wheat1
Gökhan
Hacisalihoglu,
Jonathan J.
Hart,
Yi-Hong
Wang,
Ismail
Cakmak, and
Leon V.
Kochian*
United States Plant, Soil, and Nutrition Laboratory, United States
Department of Agriculture-Agricultural Research Service, Cornell
University, Ithaca, New York 14853 (G.H., J.J.H., Y.-H.W., L.V.K.); and
Faculty of Engineering and Natural Sciences, Sabanci University,
Istanbul, Turkey (I.C.)
Zinc (Zn) is an essential micronutrient for plants. The ability of
plants to maintain significant yields under low Zn is termed Zn
efficiency (ZE) and its genetic and mechanistic basis is still not well
understood. Previously, we showed that root Zn uptake did not play a
role in ZE. In the current study, Zn-efficient and -inefficient wheat
(Triticum aestivum) genotypes were grown for 13 d
in chelate buffer nutrient solutions at low (0.1 pM), sufficient (150 pM), and high (1 µM)
Zn2+ activities and analyzed for root-to-shoot
translocation of Zn, subcellular leaf Zn distribution, and activity and
expression of the Zn-requiring enzymes in leaves. No correlation
between ZE and Zn translocation to the shoot was found. Furthermore,
total and water-soluble concentrations of leaf Zn were not associated with ZE, and no differences in subcellular Zn compartmentation were
found between Zn-efficient and -inefficient genotypes. However, the
expression and activity of the Zn-requiring enzymes copper (Cu)/Zn
superoxide dismutase (SOD) and carbonic anhydrase did correlate with
differences in ZE. Northern analysis suggested that Cu/ZnSOD gene
expression was up-regulated in the Zn-efficient genotype, Kirgiz, but
not in inefficient BDME. Under Zn deficiency stress, the very
Zn-efficient genotype Kirgiz and moderately Zn-efficient Dagdas
exhibited an increased activity of Cu/ZnSOD and carbonic anhydrase when
compared with Zn-inefficient BDME. These results suggest that
Zn-efficient genotypes may be able to maintain the functioning of
Zn-requiring enzymes under low Zn conditions; thus, biochemical Zn
utilization may be an important component of ZE in wheat.
1
This work was supported by The Republic of
Turkey (graduate fellowship to G.H.).
*
Corresponding author; e-mail LVK1{at}cornell.edu;
fax 607-255-2459.
© 2003 American Society of Plant Biologists
