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Thymidine kinases share a conserved function for nucleotide salvage and play an essential role in A rabidopsis thaliana growth and development
Author(s) -
Xu Jing,
Zhang Lin,
Yang DongLei,
Li Qun,
He Zuhua
Publication year - 2015
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.13530
Subject(s) - biology , arabidopsis thaliana , mutant , nucleotide salvage , kinase , biochemistry , pyrimidine metabolism , nucleotide , gene , thymidine kinase , function (biology) , oryza sativa , microbiology and biotechnology , genetics , enzyme , virus , herpes simplex virus , purine
Summary Thymidine kinases ( TK s) are important components in the nucleotide salvage pathway. However, knowledge about plant TK s is quite limited. In this study, the molecular function of TK s in Arabidopsis thaliana was investigated. Two TK s were identified and named At TK 1 and At TK 2 . Expression of both genes was ubiquitous, but AtTK1 was strongly expressed in high‐proliferation tissues. AtTK1 was localized to the cytosol, whereas AtTK2 was localized to the mitochondria. Mutant analysis indicated that the two genes function coordinately to sustain normal plant development. Enzymatic assays showed that the two TK proteins shared similar catalytic specificity for pyrimidine nucleosides. They were able to complement an Escherichia coli strain lacking TK activity. 5′‐Fluorodeoxyuridine (FdU) resistance and 5‐ethynyl 2′‐deoxyuridine (EdU) incorporation assays confirmed their activity in vivo . Furthermore, the tk mutant phenotype could be alleviated by nucleotide feeding, establishing that the biosynthesis of pyrimidine nucleotides was disrupted by the TK deficiency. Finally, both human and rice ( Oryza sativa ) TK s were able to rescue the tk mutants, demonstrating the functional conservation of TK s across organisms. Taken together, our findings clarify the specialized function of two TK s in A. thaliana and establish that the salvage pathway mediated by the kinases is essential for plant growth and development.