Plant Physiol, December 2002, Vol. 130, pp. 2111-2117
A Rice Mutant Defective in Si Uptake1
Jian Feng
Ma,*
Kazunori
Tamai,
Masahiko
Ichii, and
Guo Feng
Wu
Faculty of Agriculture, Kagawa University, Ikenobe 2393, Miki-cho,
Kita-gun, Kagawa 761-0795, Japan
Rice (Oryza sativa) accumulates silicon (Si)
in the tops to levels up to 10.0% of shoot dry weight, but the
mechanism responsible for high Si uptake by rice roots is not
understood. We isolated a rice mutant (GR1) that is defective in active
Si uptake by screening M2 seeds (64,000) of rice cv
Oochikara that were treated with 10
3 M sodium
azide for 6 h at 25oC. There were no phenotypic
differences between wild type (WT) and GR1 except that the leaf blade
of GR1 remained droopy when Si was supplied. Uptake experiments showed
that Si uptake by GR1 was significantly lower than that by WT at both
low and high Si concentrations. However, there was no difference in the
uptake of other nutrients such as phosphorus and potassium. Si
concentration in the xylem sap of WT was 33-fold that of the external
solution, but that of GR1 was 3-fold higher than the external solution
at 0.15 mM Si. Si uptake by WT was inhibited by metabolic
inhibitors including NaCN and 2,4-dinitrophenol and by low temperature,
whereas Si uptake by GR1 was not inhibited by these agents. These
results suggest that an active transport system for Si uptake is
disrupted in GR1. Analysis of F2 populations between GR1
and WT showed that roots with high Si uptake and roots with low Si
uptake segregated at a 3:1 ratio, suggesting that GR1 is a recessive
mutant of Si uptake.
1
This study was supported in part by NSFC (to
J.F.M.).
*
Corresponding author; e-mail maj{at}ag.kagawa-u.ac.jp; fax
81-87-891-3137.
© 2002 American Society of Plant Biologists
