The Molecular Mechanism Of ERF1 In Regulating Kiwifruit Ripening And Carnation Flower Senescence

As an important category of agriculture,horticultural products play a very important role in human life.However,most of the fruits and fresh cut flowers in horticultural products are not durable for storage,and are easy to decay and deteriorate,resulting in huge loss.Therefore,it is of great significance to study the postharvest physiology of horticultural products for improving the quality of horticultural products.Fruits and cut flowers can be classified into climacteric and non-climacteric horticultural products according to the ripening characteristics.Respiratory intensity of climacteric fruits and cut flowers increased gradually and then decreased during storage,resulting in respiratory peak,accompanied by the production of large amounts of ethylene around the climacteric period.The plant hormone ethylene has a huge impact on the postharvest preservation of horticultural products.As the only gaseous hormone that was first confirmed to be related to plant maturation and senescence,ethylene is also one of the most important causes of postharvest loss of horticultural products.ERF1 is located downstream of core protein EIN3 in the ethylene signaling pathway,and is a key transcription factor for regulating ethylene.In this study,we explored the mechanism of ethylene response factorERF1 in regulating the maturity and senescence of typical climacteric and ethylene-sensitive horticultural crops using kiwifruit and carnation as objects.The main research results are as follows:1.The AtERF1 homologous genes in Actinidia chinensis and Dianthus caryophyllus L.,AcERF1 and DcERF1,were obtained by homologous sequence alignment,phylogenetic tree and conserved domain analysis.2.The expression levels of AcERF1 and DcERF1 both decreased during the developmental phase,and both increased firstly and then decreased after ethylene treatment,which indicated that both of them were inhibited by maturation and induced by ethylene.3.The results of subcellular localization assays showed that both AcERF1 and DcERF1 were localized in the nucleus.4.The transient overexpression and virus-induced gene silencing were used to study the gene function of AcERF1 in Actinidia chinensis.When AcERF1 was overexpressed transiently,the fruit hardness increased,soluble solids content decreased,and ethylene production decreased,indicating that the transient overexpression of AcERF1 inhibited fruit ripening.Moreover,ethylene treatment increased the expression of AcERF1,which enlarged the differences in hardness,soluble solids content and ethylene production between AcERF1-overexpressed and control fruits.When AcERF1 was silenced,fruit hardness decreased,soluble solids content increased,and ethylene production increased,indicating that AcERF1 silencing accelerated fruit ripening and softening.5.After the transient overexpression of the DcERF1,the fading rate of the petal color slows down,the ion leakage rate decreases,and the expression of Dc SAG12 decreases,indicating that the overexpression of DcERF1 inhibited flower senescence.Meanwhile,the silencing of DcERF1 accelerated the fading of petal color,increased the ion leakage rate and the expression of Dc SAG12,suggesting that silencing of DcERF1 accelerated the carnation flower senescence.6.According to the binding motif of ERF transcription factor,the possible target genes ACO and ACS of AcERF1 and DcERF1 were screened out.Expression analysis showed that the expression of all these genes increased firstly and then decreased after ethylene treatment.Dual-luciferase assay results showed that AcERF1 can not activate the expression of all target genes,DcERF1 can inhibit the expression of Dc ACO4 promoters only.The results of yeast one hybridization assay showed that neither AcERF1 nor DcERF1 could directly bind to the promoters of these possible target genes.7.DcERF1 can directly bind to the DcERF1 promoter.8.AcERF1-overexpressed transgenic Arabidopsis thaliana showed characteristics of delayed growth,dwarf plant,and delayed ripeness of silique,suggesting that overexpression of AcERF1 in Arabidopsis also delayed plant development and fruit maturation.However,the overexpression of DcERF1 in Arabidopsis thaliana showed accelerated growth and advanced senescence.In conclusion,ERF1 homologous genes play negative role in kiwifruit ripening and carnation cut flower senescence.AcERF1 regulates fruit firmness,soluble solids content and ethylene synthesis to affect kiwifruit maturity,while Dc EIN3 can directly regulate DcERF1,and DcERF1 inhibits the expression of Dc ACO4 to negatively regulates ethylene synthesis in carnation flower senescence.The overexpression of AcERF1 in Arabidopsis thaliana delayed plant development and fruit maturation,however,the overexpression of DcERF1 in Arabidopsis thaliana showed accelerated growth and advanced senescence.This study provides a new basis for revealing the molecular mechanism of ethylene in regulating kiwifruit ripening and carnation cut flower senescence.