DNA double strand break repair is important for the longevity of primed seeds

Germination of many crop species is improved by priming, which facilitates pre-germinative metabolism through controlled hydration. However, priming is often associated with reduced seed longevity. Here, a screen of Arabidopsis thaliana DNA repair mutants identified dna ligase 6 and dna ligase 4 (lig6lig4) seeds as most sensitive to ageing of primed seed. Genetic analysis of wild type and lig6lig4 mutants provided mechanistic insight into the link between DNA double strand break (DSB) repair and longevity of primed seeds. RNAseq analysis of naturally aged seeds demonstrated that, while the transcriptome changes in primed aged seeds mirrors the enhancement of germination, priming significantly activated the transcriptional response to chromosomal breaks and, in lig6lig4 mutant seed, greatly exacerbated programmed cell death. These results revealed that DSB repair is an important factor in promoting longevity of primed seed, further supported by the improved longevity of primed seeds with enhanced expression of LIG6. Collectively our findings establish the genetic requirement for LIG6 in longevity of primed seed and indicate that the reduced longevity of primed seeds is mitigated by DSB repair activities. These results provide insight into the molecular basis of the reduced longevity of primed seed, important for sustainable crop production under changing climates.