Involvement of the Arabidopsis DNA glycosylase MBD4L in oxidative stress responses

TORRES JR; ALVAREZ ME

Virtual

Congreso; IV Reunión Conjunta de Sociedades de Biología de la República Argentina; 2020

Sociedades de Biología de la República Argentina

Plants accumulate reactive oxygen species (ROS) in response to biotic and abiotic stresses. These molecules can have either toxic effects on lipids, proteins, and DNA, or beneficial functions acting as signals that modulate plant growth, development or defense pathways. Paraquat (PQ) is a ROS inducing agent that inhibits photosystem I, favoring the transference of electrons to molecular oxygen for generation of superoxide anion (O2.-). An important DNA lesion generated by ROS is 7, 8-dihydro-8-oxoguanine (8-oxo-G). In Arabidopsis, AtOGG1 is the main DNA glycosylase from the base excision repair system that recognizes and eliminates 8-oxo-G from DNA. Overexpression of the AtOGG1 gene increases tolerance to PQ and mannitol. Interestingly, overexpression of the DNA glycosylase AtMBD4L gene also enhances oxidative stress tolerance, although this enzyme does not recognize 8-oxo-G as substrate in vitro. We wondered if AtMBD4L deficiency reduces the oxidative stress tolerance in vivo. To evaluate this, we used comet assay to detect DNA strand breaks in nuclei isolated from wild type and AtMBD4L mutant (mbd4l) seedlings. DNA damage levels were similar in both plants. Using plate growth assays, we performed a time course analysis of germination and root length parameters. mbd4l showed a faster germination and a longer root length than wild type plants. In addition, chlorosis at aerial tissues was lower in the mutant. Using NBT histochemical staining we evaluated the O2.- content and detected similar levels in mutant and control plants. Finally, we analyzed the AtOGG1 gene expression by RT-PCR and observed its significant induction in mbd4l, but not in wild type plants. Taken together, our results suggest that lack of AtMBD4L does not prevent the repair of nuclear DNA lesions derived from exogenous ROS treatment, but would even exacerbate the AtOGG1 activity in seedlings.