Study On Gene Expression Of Ethylene Synthesis And Signal Transduction During Embryo Germination Of Xinjiang Wild Apple

Seed germination and the formation of normal seedlings determine the propagation characteristics of plant species,have important economic sense and ecological significance.In recent years,the study of seed dormancy and germination physiology and mechanisms has been a hotspot in seed-research area.Ethylene plays an important role in the process of seed germination.Malus sieversii is a vital root stock.However,that which genes in ACS,ACO gene families and ethylene downstream signaling pathways are involved in seed germination process has not been reported.GA3,H2O2,ASA and NO can significantly promote the seed germination,but their effects on genes involved ethylene synthesis and signal transduction have not been reported.In order to preliminarily study the relative expression of genes participating in ethylene biosynthesis and signal transduction pathways during the embryo germination of Malus sieversii,and better understand the roles of GA3,H2O2,AsA and NO and their effects on gene expression in Malus sieversii embryo germination,Malus sieversii embryos were used as experimental material.The germination rate of the embryos treated with exogenous GA3,H2O2,AsA,NO and their synthesis inhibitors or scavengers were calculated.Ethylene production and the activity of ASC,ACO in the embryos were measured during the cultivation process.Meanwhile,the effects of GA3,H2O2,ASA and NO treatments on gene expression in ethylene biosynthesis and signal transduction pathways were detected.The results are as follows:1.GA3,H2O2,ASA and NO promoted the seed embryo germination by enhancing the ACS,ACO activities and accelerating ethylene biosynthesis.Treatments of different concentrations increased seed germination to different degrees.However,high concentrations of H2O2,ASA,NO inhibited germination.2.ACS gene family differentially expressed during germination of Malus sieversii seed embryos.ACS6-ACS10 had no significance in the process of seed embryo germination.The expression of ACS1,ACS5A,ACS14,ACS16 and ACS17 were significantly improved when the embryo germination activated.ACS3,ACS4,ACS5B,ACS11 and ACS13 sharply rose in the embryo germination,and among them,ACS3 and ACS13 maintained high expression during the whole process.ACS5B expression had a marked increase when radicle elongated after embryo germinating.GA3,H2O2,ASA and NO treatments not only improved the relative expression of ACS genes,but also made them in advance.3.The relative expression of four members in J CO gene family of Malus sieversii dramatically increased during the embryo germination,but their expression levels and the time occurred marked difference respectively.AC03 expressed earlier than ACO2 during embryo germination,and the expression ofACO1 was lower than that of ACO2 and ACO3.It is speculated that AC02 is associated with radicle appearance and elongation,and played a major role.In addition,AC03 and AC04 played a major role in the embryo germination,and AC04 was related to the radicle elongation after germinating.GA3,H2O2,ASA and NO could promote ethylene biosynthesis via increasing the expression of ACO family genes.After ASA treating,the peak of AC02 expressed earlier,and AC04 peak rose.Hence,it is speculated that ASA promote radicle protrusion by improving AC02 and AC04 expression.4.Ethylene receptor genes of Malus sieversii differentially expressed in the process of embryo germination.ETR1 and ETR2 expression significantly increased when the seed embryo germination activated and embryo radicle elongated,while ETR5 expressed weakly.As ethylene receptor,ERS1 and ERS2 increased dramatically in the seed embryo germination,but ERSI had a high expression in germination activation.GA3,H2O2,ASA and NO treatments improved or induced ethylene receptor genes expression of embryo to different extent,and they had different effects on different members.All treatments made ETR1 and ETR2 express in advance,and the effect of NO on ETR2 was best,however,ASA had no significant effect on ETR1 expression.GA3,H2O2,ASA and NO could induce ETR5 expression,and GA3 had a better effect.GA3,H2O2,ASA and NO enhanced the expression of ERSs,ERS2 expression was lower than these of ERS1,and the effect of GA3 treatment was best.5.The relative expression of CTR1 showed a gradual decrease during seed embryo germination of..Malus sieversii,and it was a negative regulator.GA3,H2O2,ASA and NO inhibited the expression of CTR1,and it occurred significant difference between treatments and the control.6.ERF1 had the highest expression in ERFs family during embryo germination of Malus sieversii.GA3,H2O2,ASA and NO induced or improved ERFs expression.GA3 and H2O2 had similar effect on ERF2 and ERF1.ASA and NO mainly through increasing the expression of ERF1 to promote ethylene signal transduction in the process of embryo germination.7.EIN2A and EIN2B expression markedly rose during embryo germination of Malus sieversii,and there was no significant difference.GA3 and H2O2 improved the expression of EIN2A and EIN2B,then promoted ethylene signal transduction.GA3 and H2O2had the most obvious effects on EIN2A and.EIN2B,respectively.ASA improved the expression of EIN2A and made EIN2B express in advance.it mainly played role by affecting EIN2A.NO did not improve the expression of EIN2A and EIN2B,but made they express in advance.NO promoted EIN2A and EIN2B to express in advance,thus accelerated ethylene signal transduction.8.EIL4 relative expression level was on the rise before embryo germination of Malus sieversii,as well as abundantly expressed and accumulated.GA3,H2O2,ASA and NO treatments significantly improved EIL4 expression to different extent.