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.