Poster: Cytoskeleton: Structure & Function

Abs # 1120: IPC-resistant Nicotiana lines as a tool for investigation of phenylcarbamate and benzimidazole interaction with plant tubulin.

Presenter:	Yemets, Alla , alyemets@univ.kiev.ua
Authors	Yemets, Alla  (A)   Stelmakh, O.  (A)   Kravets, Ye.  (A)   Nyporko, A.  (A)   Blume, Ya.B.  (A)
Affiliations:	(A): Institute of Cell Biol. & Genet. Engrg., Natl. Academy of Science

N-phenylcarbamates (NPCs)and benzimidazoles (BZs), well known antimicrotubular agents, are used widely as herbicides and broad-spectrum fungicides, respectively. Although it is discussed that NPCs target MTOCs rather than disrupt microtubules directly, some results show that they do in fact bind plant tubulin (Mizuno et al., 1981; Young & Lewandowski, 2000). NPCs and BZs can compete for the site(s) of binding with b-tubulin. BZs interact specifically with different b-tubulins and BZ-resistance may be caused by point mutations in b-tubulin which replace Glu-198 with either Ala, Val, or Gly, or Phe-200 with Tyr (Hollomon et al., 1994). Amino acid substitution in position 198 of b-tubulin of Neurospora crassa leads to negative cross-resistance to NPCs (Fujimura et al., 1992), but changes Phe from Leu-250, Val from Ala-165, and Ala from Thr-237 are responsible for NPC cross-resistance (Fujimura et al., 1994). Using 3-D computer modeling we have revealed all these mutations are located in the same area closely to an intradimeric contact, but Leu-250 and Ala-165 are exposed only on b-tubulin surface. BZs and NPCs having very close chemical structure can share the common binding site on b-tubulin, but their docking peculiarities should be different. To continue clarifying the mechanism of NPCs interaction with plant tubulin the mutants of Nicotiana sp. resistant to 30 mM isopropyl-N-phenylcarbamate (IPC) were produced. The mutants were resistant to such NPC as EPC. IPC did not disrupt their cell cycle progression, but mutants were infertile. The infertility correlated with disturbances in meiosis leading to abnormality of pollen producing. Cross-resistance/sensitivity to BZs as well as biochemical analysis of the mutants is under investigation now.