The stability of cortical microtubules depends on their orientation.
Auxin controls the orientation of cortical microtubules in maize coleoptile segments. We used tyrosinylated alpha-tubulin as a marker to assess auxin-dependent changes in microtubule turnover. Auxin-induced tyrosinylated alpha-tubulin, correlated with an elevated sensitivity of growth to antimicrotubular compounds such as ethyl-N-phenylcarbamate (EPC). We determined the affinity of alpha-tubulin to EPC and found that it was dramatically increased when the tubulin was de-tyrosinylated. By proteolytic cleavage of the carboxy terminal tyrosine, such an increased affinity could be induced in vitro. Thus, the auxin-induced sensitivity of growth to EPC is not caused by an increased affinity for this inhibitor, but caused by a reduced microtubule turnover. Double visualization assays revealed that the transverse microtubules induced by auxin consist predominantly of tyrosinylated alpha-tubulin, whereas the longitudinal microtubules induced by auxin depletion contain de-tyrosinylated alpha-tubulin. The results are discussed in terms of direction-dependent differences in the lifetime of microtubules.
Wiesler
Bodo
B
Institut für Biologie II/Botanik, Schänzlestrasse 1, Universität Freiburg, D-79104 Freiburg, Germany.
Wang
Qi-Yan
QY
Nick
Peter
P
D000595:Amino Acid Sequence; D001665:Binding Sites; D002219:Carbamates / Q000494:pharmacology; D003078:Colchicine / Q000494:pharmacology; D018548:Cotyledon / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D004136:Dinitrobenzenes / Q000494:pharmacology; D007210:Indoleacetic Acids / Q000494:pharmacology; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism*; D008969:Molecular Sequence Data; D048448:Phenylcarbamates; D017386:Sequence Homology, Amino Acid; D013424:Sulfanilamides; D014274:Trifluralin / Q000494:pharmacology; D014404:Tubulin / Q000235:genetics / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism; D014520:Urethane; D003313:Zea mays / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*
D002219:Carbamates; D004136:Dinitrobenzenes; D007210:Indoleacetic Acids; D048448:Phenylcarbamates; D013424:Sulfanilamides; D014404:Tubulin; D014520:Urethane; D014443:Tyrosine; C012465:oryzalin; C030737:indoleacetic acid; D014274:Trifluralin; D003078:Colchicine; C008866:phenylurethane