Abstract
Tyrosyl-DNA phosphodiesterase 1 (Tdp1) is involved in DNA repair pathways as it mends the topoisomerase I—DNA covalent complexes. In plants, a small Tdp1 gene family, composed by Tdp1α and Tdp1β genes, was identified, but the roles of these genes in abiotic stress responses are not fully understood. To investigate their specific stress response patterns, the present study made use of bioinformatic and molecular tools to look into the Tdp1β gene function, so far described only in the plant kingdom, and compare it with Tdp1α gene coding for the canonical, highly conserved α isoform. The expression profiles of Tdp1α and Tdp1β genes were examined under abiotic stress conditions (cold, heat, high osmolarity, salt, and UV-B) in two model species, Arabidopsis thaliana and Medicago truncatula. The two isoforms of topoisomerase I (TOP1α and TOP1β) were also taken into consideration in view of their known roles in DNA metabolism and cell proliferation. Data relative to gene expression in Arabidopsis were retrieved from the AtGenExpress microarray dataset, while quantitative Real-Time PCR was carried out to evaluate the stress response in M. truncatula cell cultures. These analyses revealed that Tdp1β gene expression was enhanced during the first hour of treatment, whereas Tdp1α enhanced expression succeeded at subsequent timepoints. In agreement with the gene-specific responses to abiotic stress conditions, the promoter regions of Tdp1α and Tdp1β genes are well equipped with stress-related cis-elements. An in-depth bioinformatic characterization of the HIRAN motif, a distinctive feature of the Tdp1β protein, showed its wide distribution in chromatin remodeling and DNA repair proteins. The reported data suggests that Tdp1β functions in the early response to abiotic stresses.
Highlights
Tyrosyl-DNA phosphodiesterase 1 (Tdp1, EC: 3.1.4.-) breaks the covalent 30 -phosphotyrosyl bond between the DNA termini and the catalytic tyrosine residue of DNA topoisomerase I, removing the highly cytotoxic stabilized topoisomerase I—DNA covalent complexes that impair DNA replication and transcription [1]
Tdp1 is strongly linked complex functions in DNA repair [26], mutationsIn in human its catalytic sites to investigate theirwith implication in plant development and whereas stress response
Tdp1α gene in damage repair and stress response associated with serious diseases [27]
Summary
Tyrosyl-DNA phosphodiesterase 1 (Tdp, EC: 3.1.4.-) breaks the covalent 30 -phosphotyrosyl bond between the DNA termini and the catalytic tyrosine residue of DNA topoisomerase I (topo I), removing the highly cytotoxic stabilized topoisomerase I—DNA covalent complexes that impair DNA replication and transcription [1]. From animals, two distinct Tdp isoforms are found in plants, as reported by Macovei et al [2] in the model legume Medicago truncatula. Genes 2017, 8, 305 isoforms are encoded by MtTdp1α and MtTdp1β genes, which are upregulated in M. truncatula plants in response to heavy metal and osmotic stresses as well as during seed imbibition [2,3,4]. Additional work provided further information on the possible involvement of the Tdp1β gene in the plant stress response. Santos et al [5] showed the upregulation of Tdp1β gene in Medicago sativa suspension cultures exposed to genotoxic doses of CdSe/ZnS quantum dots, highlighting a strong correlation with
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