The SSRP1 subunit of the histone chaperone FACT is required for seed dormancy in Arabidopsis

SSRP1 is a subunit of the histone chaperone FACT that associates with elongating RNA polymerase II (RNAPII) along the transcribed region of genes. FACT facilitates transcriptional elongation by destabilising nucleosomes in the path of RNAPII, assisting efficient transcription of chromatin templates. In contrast to wild type seeds, freshly harvested seeds of the Arabidopsis ssrp1 mutant germinate efficiently, exhibiting reduced seed dormancy. In line with this phenotype, the ssrp1 seeds have decreased transcript levels of the DOG1 gene, which is a known quantitative trait locus (QTL) for seed dormancy. Analysis of ssrp1 plants harbouring an additional copy of DOG1 show increased levels of DOG1 transcript and consistently more robust seed dormancy. Therefore, our findings indicate that SSRP1 is a novel factor required for the efficient expression of DOG1 and hence a modulator of seed dormancy in Arabidopsis.