Seed dormancy cycling in A rabidopsis: chromatin remodelling and regulation of DOG 1 in response to seasonal environmental signals

Summary The involvement of chromatin remodelling in dormancy cycling in the soil seed bank ( SSB ) is poorly understood. Natural variation between the winter and summer annual A rabidopsis ecotypes C vi and B ur was exploited to investigate the expression of genes involved in chromatin remodelling via histone 2 B ( H 2 B ) ubiquitination/de‐ubiquitination and histone acetylation/deacetylation, the repressive histone methyl transferases CURLY LEAF ( CLF ) and SWINGER ( SWN ), and the gene silencing repressor ROS 1 ( REPRESSOR OF SILENCING 1) and promoter of silencing KYP / SUVH 4 ( KRYPTONITE ), during dormancy cycling in the SSB . ROS 1 expression was positively correlated with dormancy while the reverse was observed for CLF and KYP / SUVH 4 . We propose ROS 1 dependent repression of silencing and a sequential requirement of CLF and KYP / SUVH 4 dependent gene repression and silencing for the maintenance and suppression of dormancy during dormancy cycling. Seasonal expression of H 2 B modifying genes was correlated negatively with temperature and positively with DOG 1 expression, as were histone acetyltransferase genes, with histone deacetylases positively correlated with temperature. Changes in the histone marks H 3 K 4me3 and H 3 K 27me3 were seen on DOG 1 ( DELAY OF GERMINATION 1 ) in C vi during dormancy cycling. H 3 K 4me3 activating marks remained stable along DOG 1 . During relief of dormancy, H 3 K 27me3 repressive marks slowly accumulated and accelerated on exposure to light completing dormancy loss. We propose that these marks on DOG 1 serve as a thermal sensing mechanism during dormancy cycling in preparation for light repression of dormancy. Overall, chromatin remodelling plays a vital role in temporal sensing through regulation of gene expression.