Chang Hsin-Yu, Smertenko Andrei P, Igarashi Hisako, Dixon David P, Hussey Patrick J
The Integrative Cell Biology Laboratory, School of Biological and Biomedical Sciences, University of Durham, South Road, Durham, DH1 3LE, UK.
J Cell Sci. 2005 Jul 15;118(Pt 14):3195-201. doi: 10.1242/jcs.02433.
Plant microtubules are intrinsically more dynamic than those from animals. We know little about the dynamics of the interaction of plant microtubule-associated proteins (MAPs) with microtubules. Here, we have used tobacco and Arabidopsis MAPs with relative molecular mass 65 kDa (NtMAP65-1a and AtMAP65-1), to study their interaction with microtubules in vivo. Using fluorescence recovery after photobleaching we report that the turnover of both NtMAP65-1a and AtMAP65-1 bound to microtubules is four- to fivefold faster than microtubule treadmilling (13 seconds compared with 56 seconds, respectively) and that the replacement of NtMAP65-1a on microtubules is by random association rather than by translocation along microtubules. MAP65 will only bind polymerised microtubules and not its component tubulin dimers. The turnover of NtMAP65-1a and AtMAP65-1 on microtubules is similar in the interphase cortical array, the preprophase band and the phragmoplast, strongly suggesting that their role in these arrays is the same. NtMAP65-1a and AtMAP65-1 are not observed to bind microtubules in the metaphase spindle and their rate of recovery is consistent with their cytoplasmic localisation. In addition, the dramatic reappearance of NtMAP65-1a on microtubules at the spindle midzone in anaphase B suggests that NtMAP65-1a is controlled post-translationally. We conclude that the dynamic properties of these MAPs in vivo taken together with the fact that they have been shown not to effect microtubule polymerisation in vitro, makes them ideally suited to a role in crossbridging microtubules that need to retain spatial organisation in rapidly reorganising microtubule arrays.
植物微管本质上比动物微管更具动态性。我们对植物微管相关蛋白（MAPs）与微管相互作用的动态了解甚少。在此，我们使用了相对分子质量为65 kDa的烟草和拟南芥MAPs（NtMAP65 - 1a和AtMAP65 - 1），来研究它们在体内与微管的相互作用。通过光漂白后的荧光恢复实验，我们发现与微管结合的NtMAP65 - 1a和AtMAP65 - 1的周转速度比微管踏车运动快四到五倍（分别为13秒和56秒），并且微管上NtMAP65 - 1a的替换是通过随机结合而非沿微管的易位。MAP65仅与聚合的微管结合，而不与组成它的微管蛋白二聚体结合。在间期皮层阵列、前期带和成膜体中，NtMAP65 - 1a和AtMAP65 - 1在微管上的周转情况相似，这强烈表明它们在这些阵列中的作用相同。在中期纺锤体中未观察到NtMAP65 - 1a和AtMAP65 - 1与微管结合，它们的恢复速率与它们在细胞质中的定位一致。此外，在后期B纺锤体中区微管上NtMAP65 - 1a的显著重新出现表明NtMAP65 - 1a是在翻译后受到调控的。我们得出结论，这些MAPs在体内的动态特性，以及它们在体外已被证明不影响微管聚合这一事实，使它们非常适合在快速重组的微管阵列中需要保持空间组织的微管交联中发挥作用。
