In rice, Oryzalin and abscisic acid differentially affect tubulin mRNA and protein levels

The effect 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 elongation, caused loss of cell anisotropy and the disappearance of the cortical microtubule array. Under these conditions the amounts of alpha- and beta-tubulin protein, but not mRNA, were heavily reduced. Similar data were also obtained in coleoptile segments treated with different concentrations of Oryzalin. However, when coleoptile elongation was inhibited by cis-abscisic acid, remarkable decreases in alpha- and beta-tubulin accumulation were observed 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 different levels, mRNA or protein, in response to Oryzalin or abscisic acid treatments.