Abstract
Abscisic acid (ABA) acts as an important plant hormone in regulating various aspects of plant growth and developmental processes particularly under abiotic stress conditions. An increased ABA level in plant cells inhibits DNA replication and cell division, causing plant growth retardation. In this study, we have investigated the effects of ABA on the growth responses of some major loss-of-function mutants of DNA double-stand break (DSB) repair genes in Arabidopsis during seed germination and early stages of seedling growth for understanding the role of ABA in the induction of genome instability in plants. A comparative analysis of ABA sensitivity of wild-type Arabidopsis and the knockout mutant lines related to DSB sensors, including atatm, atatr, the non-homologous end joining (NHEJ) pathway genes, and mutants related to homologous recombination (HR) pathway genes showed relatively enhanced sensitivity of atatr and HR-related mutants to ABA treatment. The expression levels of HR-related genes were increased in wild-type Arabidopsis (Col-0) during seed germination and early stages of seedling growth. Immunoblotting experiments detected phosphorylation of histone H2AX in wild-type (Col-0) and DSB repair gene mutants after ABA treatment, indicating the activation of DNA damage response due to ABA treatment. Analyses of DSB repair kinetics using comet assay under neutral condition have revealed comparatively slower DSB repair activity in HR mutants. Overall, our results have provided comprehensive information on the possible effect of ABA on DNA repair machinery in plants and also indicated potential functional involvement of HR pathway in repairing ABA induced DNA damage in Arabidopsis.
Highlights
Plants are frequently exposed to various environmental stress conditions and have evolved with highly complex and elaborated mechanisms for integrating different stress signals and respond to them in a coordinated and comprehensive manner to adjust and survive underPLOS ONE | DOI:10.1371/journal.pone.0169294 January 3, 2017Cross Talk between Abscisic acid (ABA) Signaling and DNA Damage Response Pathway in PlantsAbbreviations: ABA, abscisic acid; double-strand breaks (DSBs), doublestrand breaks; HR, homologous recombination; NHEJ, non-homologous end joining; Pol, polymerase; qRT-PCR, quantitative real-time PCR.such stress conditions
DNA ligase 4-XRCCA4 complex and Pol λ are functional in processing broken DNA ends and repair synthesis in NHEJ mediated DSB repair [23,36]
The phenotypic responses of wild-type and DSB-related mutant lines were analysed in presence of different concentrations of exogenously applied ABA during seed germination and post-germination seedling growth
Summary
Cross Talk between ABA Signaling and DNA Damage Response Pathway in Plants Plants respond to abiotic stresses predominantly via the rapid changes in the expression levels of the stress responsive genes at the transcriptional level and by means of accumulation of metabolic compounds, which help in stress adaptation. Abiotic stresses, such as UV-radiation, high soil salinity, water deficit, low temperature, nutrient deficiencies, herbicide treatment and heavy metal toxicity frequently induce the accumulation of the phytohormone abscisic acid (ABA) in plants [1,2,3]. Genetic and molecular studies have helped in the identification and characterization of several genes involved in ABA responses in plants [8,9]
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