A Single Amino-Acid Substitution at Lysine 40 of an Arabidopsis thaliana α-tubulin Causes Extensive Cell Proliferation and Expansion Defects

• Published in: Journal of integrative plant biology 2013-03, Vol.55 (3), p.209-220
• Main Authors: Xiong, Xue, Xu, Deyang, Yang, Zhongnan, Huang, Hai, Cui, Xiaofeng
• Format: Article
• Language: English
• Subjects: acetylation; alanine; Arabidopsis; Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis Proteins - chemistry; Arabidopsis Proteins - metabolism; Arabidopsis thaliana; arginine; cell division; Cell Proliferation; expansion; gene expression; Gene Expression Regulation, Plant; glutamine; lysine; microtubule; microtubules; Microtubules - metabolism; Plants, Genetically Modified - genetics; Plants, Genetically Modified - metabolism; polymers; proteins; transgenic plants; Tubulin - chemistry; Tubulin - metabolism; vertebrates; α-tubulin
• ISSN: 1672-9072; 1744-7909
• DOI: 10.1111/jipb.12003

Microtubules are highly dynamic cytoskeletal polymers of α/β-tubulin heterodimers that undergo multiple post-translational modifications essential for various cellular functions in eukaryotes. The lysine 40 （K40） is largely conserved in α-tubulins in many eukaryote species, and the post-translational modification by acetylation at K40 is critical for neuronal development in vertebrates. However, the biological function of K40 of α-tubulins in plants remains unexplored. In this study, we show in Arabidopsis thaliana that constitutive expression of mutated forms of α-tubulin6 （TUA6） at K40 （TUA6K40A or TUA6K40Q ）, in which K40 is replaced by alanine or glutamine, result in severely reduced plant size. Phenotypic characterization of the 35S：TUA6K40A transgenic plants revealed that both cell proliferation and cell expansion were affected. Cytological and biochemical analyses showed that the accumulation of α- and β-tubulin proteins was significantly reduced in the transgenic plants, and the cortical microtubule arrays were severely disrupted, indicating that K40 of the plant α-tubulin is critical in maintaining microtubule stability. We also constructed 35S：TUA6K40R transgenic plants in which K40 of the engineered TUA6 protein is replaced by an arginine, and found that the 35S：TUA6K40R plants were phenotypically indistinguishable from the wild-type. Since lysine and arginine are similar in biochemical nature but arginine cannot be acetylated, these results suggest a structural importance for K40 of α-tubulins in cell division and expansion.