Study On The Effects Of Histone Deacetylase Inhibitors On Strawberry Fruit Ripening

Strawberry(Fragaria × ananassa Duch.)is one of the important horticultural crops.With the expansion of strawberry planting area in our country and people’s requirements for food quality,the study on ripening process of strawberry has become an interesting research area.Strawberries have a high water content,accounting for 90%to 95%.The fruits are fresh and tender.They are easily affected by external environmental factors during the ripening process,and are susceptible to microorganism infection after harvest,which seriously restricts the economic benefits of strawberries and the development of the strawberry industry.Fruit ripening is a complex process involving changes in color,texture,aroma,and flavor etc.Epigenetic modification can regulate the ripening of strawberry fruit,but the regulatory role of histone deacetylation during strawberry fruit ripening is not yet clear.Histone acetylation is a very important epigenetic modification regulating gene expression.Histone acetylation levels are affected by the balance between histone deacetylase and histone acetyl transferase.Histone deacetylase inhibitors can inhibit histone deacetylase activity and further regulate gene expressions.In this study,we apply the strawberry fruits with different types of histone deacetylase inhibitors to study the effect of histone deacetylase inhibitors on fruit ripening.Then,the fruits treated with the histone deacetylae inhibitor TSA(Trichostatin A)and IAA(Auxin)for 12h and 4d were used as materials to study the regulatory effect of histone deacetylation on strawberry fruit ripening.Further analyse of differentially expressed genes related to firmness,anthocyanin,abscisic acid and auxin are performed.The results are as follows:1.The fruits of strawberry cultivar "Hongyan" at the white stage were applied with different concentrations of histone modifier inhibitors such as GSK126,sodium butyrate,nicotinamide and TSA to study their effects on strawberry fruit ripening.The concentration of GSK126 are 0 μM(control group),1 μM,10 μM,50 μM and 100 μM.The concentration of sodium butyrate are 0 μM(control group),500 μM,2mM and 10mM The concentration of nicotinamide are 0 μM(control group)1mM,3mM and 10mM.The concentration of TSA are 0 μM(control group),4 μM,20 μ M and 100 μM.The concentration of IAA are 0 μ M(control group),200 μM and 500 μ M.Statistics shows that sodium butyrate and nicotinamide have no significant effect on strawberry ripening process,while GSK126 and TSA inhibit strawberry ripening,in which TSA has a more significant inhibitory effect It is speculated that histone deacetylation may be involved in the fruit ripening process.2.The fruits of strawberry cultivar "Hongyan" at the white stage are applied with TSA and IAA,and the fruit materials with 12h and 4d treatment are collected for RNA-sequencing.In total,19,823 and 2,879 genes are detected as differentially expressed genes after 12 hours and 4 days treatment,respectively.It is speculated that TSA has a large transient effect on the expression of genes during strawberry maturation.The differentially expressed genes after TSA treatment are mainly involved in metabolic pathways and secondary metabolic biosynthetic pathways.Both TSA and IAA can inhibit strawberry maturation.The differentially expressed genes of the two treatments are up-regulated in phenylpropanoid biosynthesis,phenylalanine metabolism and other pathways,and down-regulated in glutathione metabolism and linolenic acid metabolism.We focused on the expression of genes related to firmness,anthocyanin biosynthesis,auxin and abscisic acid pathways after 12 hours of TSA treatment.The transcriptome data show that compared with the control group,the expression of XTH25,a gene involved in cell wall remodeling,was up-regulated by 150.8-fold;the expression level of EXPR-1,an expansin gene involved in promoting cell wall softening,is down-regulated by 3.7 times.Meanwhile,18 genes related to the anthocyanin synthesis pathway are down-regulated upon 12 hours of TSA treatment.Among them,the expression level of DFR2,a key gene for anthocyanin synthesis,is reduced by 13.2-fold.Abscisic acid is a promoting factor for strawberry fruit ripening,while auxin is an inhibitory factor.TSA treatment affects the expression of abscisic acid and auxin pathway-related genes as well.For example,protein phosphatase gene PP2C7,a key negative regulator of ABA pathway,is up-regulated by 6.3-fold The auxin responsive transcription factor ARF8 is up-regulated by 6.1-fold.The inhibition of abscisic acid pathway and the up-regulation of auxin pathway may contribute to the inhibitory role of TSA in strawberry fruit ripening.