A Single Amino-acid Substitution At Lysine40of An Arabidopsis α-tubulin Causes Extensive Cell Proliferation And Expansion Defects

Microtubules (MTs) are highly dynamic cytoskeletal polymers of/-tubulin heterodimersthat undergo multiple posttranslational modifications essential for various cellular functions ineukaryotes. The lysine40(K40) is largely conserved in-tubulins in many eukaryote species,and the post-translational modification by acetylation at K40is critical for neuronal developmentin vertebrates. However, the biological function of K40of-tubulins in higher plants remainsunexplored. Here we show that constitutive expression of a mutated form of-tubulin6(TUA6)at K40(TUA6K40A), in which the lysine is replaced by alanine, resulted in severely reduced plantsize. Phenotypic characterization of the35S:TUAK40Atransgenic plants revealed that both cellproliferation and cell expansion were affected. Moreover, cytological and biochemical analysesshowed that the accumulation of-and-tubulin proteins was significantly reduced in thetransgenic plants, and the cortical MT arrays were severely disrupted. These data suggest thatK40of the plant-tubulin is critical in maintaining MT stability, and thus is important for celldivision and expansion during plant growth and development.