In rice, Oryzalin and abscisic acid di erentially a ect tubulin mRNA and protein levels

The e€ect of the anti-microtubular drug
Oryzalin (3,5-dinitro-N4,N4-dipropylsulfanilamide) on
growth and elongation of rice (
Oryza sativa
L. cv.
Arborio) roots and coleoptiles was investigated. At
100 nM, Oryzalin strongly reduced primary root elon-
gation, caused loss of cell anisotropy and the disappear-
ance of the cortical microtubule array. Under these
conditions the amounts of
a
- and
b
-tubulin protein, but
not mRNA, were heavily reduced. Similar data were also
obtained in coleoptile segments treated with di€erent
concentrations of Oryzalin. However, when coleoptile
elongation was inhibited by
cis
-abscisic acid, remarkable
decreases in
a
-and
b
-tubulin accumulation were ob-
served to occur at the mRNA level but not at the protein
level. The transcriptional decreases could be reversed by
re-addition of 3-indole acetic acid. Altogether, these data
indicate that rice tubulin accumulation can be controlled
at di€erent levels, mRNA or protein, in response to
Oryzalin or abscisic acid treatments.