Functional Characterization Of Arabidopsis Histone H3K4 Demethylase JMJ17 In Dehydration Stress And Abscisic Acid Response

Drought is a major constraint for crop productivity in the world,which threatens food security.The plants have evolved for more complicated and precise mechanism in order to cope with drought as they cannot escape from harmful environments.Understanding mechanism of stress response will help us to achieve new varieties resistant to drought stress.Histone modification is one of the most significant means of epigenetic regulation,and can change the conformation of chromatin thus affects transcription.Here,we document that a histone demethylase,JMJ17,plays crucial roles in response to dehydration stress and abscisic acid(ABA)in Arabidopsis thaliana.In our study we focused on roles of histone demethylation in response to dehydration stress and ABA,and depicted the mechanism of JMJ17 regulation in dehydration stress and ABA response.Combination of molecular biology and bioinformatic analyses revealed that a mutation in JMJ17 caused an ectopic increase in genome-wide H3K4me3 levels and activated a plethora of dehydration stress-and ABA-responsive genes.The main conclusions of this study are as follows:(1)By taking advantage of subcellular localization and expression patterns of JMJ17,we found that JMJ17 localizes in nucleus and JMJ17 expresses in true leaves,primary and secondary roots,floral tissues and siliques.(2)jmj17 loss-of-function mutants displayed dehydration stress tolerance and ABA hypersensitive phenotypes comparing to wild type.(3)We confirmed that JMJ17 specifically demethylates H3K4me1/2/3 in vitro and in vivo.Moreover,jmj17-1 and JMJ17[H79A/E81A] displayed increased survival rates compared with Col-0 and complementation lines under long-term dehydration stress.These results indicate that H3K4 demethylase activity of JMJ17 is required for the dehydration stress response.(4)During vegetative growth,no noticeable phenotypic differences were observed among the single and double mutant lines,whereas the triple mutant displayed larger rosette leaves.During the reproductive stage,jmj17-1 jmj14-1 jmj16-1 triple mutant flowered earlier than jmj14-1,jmj17-1 jmj14-1 and jmj17-1 jmj16-1.These results indicate that JMJ14,JMJ16,and JMJ17,play redundant roles during vegetative and reproductive development.(5)Systematic combination of ChIP-seq and RNA-seq analyses reveal that JMJ17 impacts both H3K4me3 levels and gene expression under dehydration stress.(6)jmj17-1 ost1-3 double mutant and ost1-3 single mutant plants showed similar survival rates under dehydration stress.Besides,following the ChIP-qPCR,we concluded that JMJ17 modulates H3K4me3 levels at OST1 locus that in turn affects RNAPII occupancy,which is essential for gene transcription.(7)jmj17-1 abi5-7 double mutant displayed similar sensitivity compared to that of abi5-7 single mutant in terms of seed germination and seedling growth.Furthermore,ABI5 transcription was affected owing to fluctuation of H3K4me3 level regulated by JMJ17.(8)JMJ17 interactes with WRKY40 in vivo and is functionally associated with WRKY40 in seed germination and seedling growth regulated by ABA.Taken together,our findings unravel that histone demethylase JMJ17 plays crucial roles in response to dehydration stress and ABA in Arabidopsis thaliana.