Abstract
Proper organization of cortical microtubule arrays is essential for anisotropic growth in plants but how distinct array patterns are formed is not understood. Here we report a relationship between microtubule dynamics and array organization using transgenic plants expressing modified tubulins. When GFP or HA epitope tag was fused to the N-terminus of tubulins and expressed in Arabidopsis plants, these tubulins were incorporated into microtubule polymers. Plants expressing modified β-tubulins were phenotypically normal and possessed transversely oriented cortical arrays in the epidermal cells of the root elongation zone; however, expression of the modified Α-tubulins caused right-handed helical growth, and left-handed array organization. In cells expressing the modified Α-tubulins, GFP-AtEB1b (End Binding1) labeled larger regions of the microtubule end and microtubule depolymerization was highly suppressed. We propose that the introduced N-terminus appendage of Α-tubulin inhibits its GTPase activating function, thus producing polymerization-prone microtubules with an extended GTP-cap.
