Maize Thymidine Kinase Activity Is Present throughout Plant Development and Its Heterologous Expression Confers Tolerance to an Organellar DNA-Damaging Agent
Manuela Nájera-Martínez,
José Antonio Pedroza-García,
Luis Jiro Suzuri-Hernández,
Christelle Mazubert,
Jeannine Drouin-Wahbi,
Jorge Vázquez-Ramos,
Cécile Raynaud,
Javier Plasencia
Affiliations
Manuela Nájera-Martínez
Departamento de Bioquímica, Facultad de Química, Universidad Nacional Autónoma de México, Ciudad de México 04510, Mexico
José Antonio Pedroza-García
Departamento de Bioquímica, Facultad de Química, Universidad Nacional Autónoma de México, Ciudad de México 04510, Mexico
Luis Jiro Suzuri-Hernández
Departamento de Bioquímica, Facultad de Química, Universidad Nacional Autónoma de México, Ciudad de México 04510, Mexico
Christelle Mazubert
Institute of Plant Sciences Paris-Saclay (IPS2), CNRS, INRA, University Paris-Sud, University of Evry, Paris University, Sorbonne Paris-Cite, University of Paris-Saclay, Batiment 630, 91405 Orsay, France
Jeannine Drouin-Wahbi
Institute of Plant Sciences Paris-Saclay (IPS2), CNRS, INRA, University Paris-Sud, University of Evry, Paris University, Sorbonne Paris-Cite, University of Paris-Saclay, Batiment 630, 91405 Orsay, France
Jorge Vázquez-Ramos
Departamento de Bioquímica, Facultad de Química, Universidad Nacional Autónoma de México, Ciudad de México 04510, Mexico
Cécile Raynaud
Institute of Plant Sciences Paris-Saclay (IPS2), CNRS, INRA, University Paris-Sud, University of Evry, Paris University, Sorbonne Paris-Cite, University of Paris-Saclay, Batiment 630, 91405 Orsay, France
Javier Plasencia
Departamento de Bioquímica, Facultad de Química, Universidad Nacional Autónoma de México, Ciudad de México 04510, Mexico
Thymidine kinase 1 (TK1) phosphorylates thymidine nucleosides to generate thymidine monophosphate. This reaction belongs to the pyrimidine salvage route that is phylogenetically conserved. In the model plant Arabidopsis thaliana, TK activity contributes to maintain nuclear and organellar genome integrity by providing deoxythymidine-triphosphate (dTTP) for DNA synthesis. Arabidopsis has two TK1 genes (TK1a and TK1b) and double mutants show an albino phenotype and develop poorly. In contrast, maize (Zea mays L.) has a single TK1 (ZmTK1) gene and mutant plants are albino and display reduced genome copy number in chloroplasts. We studied the role of ZmTK1 during development and genotoxic stress response by assessing its activity at different developmental stages and by complementing Arabidopsis tk1 mutants. We found that ZmTK1 transcripts and activity are present during germination and throughout maize development. We show that ZmTK1 translocation to chloroplasts depends on a 72-amino-acid N-signal and its plastid localization is consistent with its ability to complement Arabidopsis tk1b mutants which are hypersensitive to ciprofloxacin (CIP), a genotoxic agent to organellar DNA. Also, ZmTK1 partly complemented the Arabidopsis double mutant plants during development. Our results contribute to the understanding of TK1 function in monocot species as an organellar enzyme for genome replication and repair.
