The DNA glycosylase MBD4L contributes to DNA repair during seed development and germination

LESCANO IGNACIO; TORRES JR; NOTA MF; CECCHINI NM; ALVAREZ ME

Congreso; RAFV Conference XXXIII Argentinian meeting of Plant Physiology; 2021

Genome damage accumulates in the embryo of seeds, specially under stressful conditions (i.e. high temperatures) resulting in aged seeds with decreased vigor and viability. In addition, both seed development and germination are coupled with cycles of dehydration and rehydration with increased metabolism and high levels of reactive oxygen species, resulting in oxidation of DNA bases and strand breaks. Consequently, DNA must be repaired prior germination to prevent genomic damage from being fixed after cell division. The base excision repair (BER) system contributes to this end by using DNA glycosylases that excise damaged bases from the genome. Here, we analyzed seed phenotypes associated with the deficiency of the Arabidopsis DNA glycosylase MBD4L (Methyl-Binding Domain Protein 4-Like). Both silique and seed size, as well as the germination rate were decreased in MBD4L mutants (mdb4l) compared to wild-type plants. The decreased germination rate of mbd4l seeds was exacerbated after long-term aging at controlled conditions or short heat treatments. Germination rate under control and heat conditions were rescued by overexpressing MBD4L isoforms in the mutant background. Interestingly, seeds expressing the shorter isoform presented the highest germination rates. Comet assays and gene expression analysis showed that BER was compromised in mbd4l mutants. Moreover, promoter studies indicated that MBD4L expression was higher at early stages of seed development. Our results suggest that MBD4L contributes to DNA repair by activating the BER system prior seed germination to maintain genome integrity, cell viability, and accurate transmission of genetic information.