The DNA glycosylase MBD4L contributes to DNA repair and preserves seed viability after heat-induced ageing

LESCANO CI; TORRES JR; CECCHINI NM; ALVAREZ MARÍA E

Workshop; Embo workshop Molecular responses of plants facing climate change; 2023

Germination represents a key developmental transition in plant lifecycle and is critical for seedling establishment. Seed desiccation, storage and imbibition are associated with high levels of reactive oxygen species (ROS) that results in oxidation of DNA bases and strand breaks. Moreover, heat shocks exacerbate ROS-induced genomic damage resulting in aged seeds with decreased vigor and viability. Consequently, DNA must be repaired prior germination to maintain genomic integrity and ensure cell survival and accurate transmission of genetic information. The base excision repair (BER) contributes to this end by using DNA glycosylases to excise damaged bases from the genome. The analysis of the expression pattern of Arabidopsis DNA glycosylases showed that MBD4L (methyl-binding domain protein 4 like) mRNAs strongly accumulate during seed desiccation, keeping a high abundance during first hours of imbibition. Moreover, MBD4L transcripts were strongly up-regulated during imbibition of seeds preincubated at 37°C or 45°C. We further analyzed germinationphenotypes associated with the deficiency/ overexpression of MBD4L under control and heat stress conditions. Interestingly, mbd4l mutants showed late germination under basal conditions, and lost viability after heat treatments. These phenotypes were rescued or improved by overexpressing MBD4L in the mbd4l-1 mutant background. Further expression analysis and comet assays showed that both BER system and DNA repair were significantly compromised in the mbd4l-1 mutant. Our results suggest that MBD4L contributes to DNA repair required for proper seed germination, playing a major role in preserving seed viability after heat shock episodes.