| Homeobox 1 in Malus×domestica(MdHB1)is a transcription factor that belongs to Homeodomain-Leucine zipper I(HD-ZipI)protein subfamily.According to previous reports,MdHB1 could regulate ethylene synthesis by binding with the MdACO1 promoter.The promoter region of MdHB1 was cloned from the Royal Gala apple genome and this research was conducted in Nicotiana tabacum and supported by Agrobacterium-mediated transient transformation and bioinformatics analysis.The results are as follows:1、After the sequence analysis through bioinformatics software,Transcriptional start site(TSS),CAAT BOX,TATA BOX are located in 266 bp,319bp,308 bp from the upstream of ATG(initiation code).The cis-acting elements that respond to hormones and environmental stresses were identified in the promoter region,such as ERE,ABRE,ARE,G-Box etc.2、Deletion analysis of the MdHB1 promoter showed that the GUS gene could be activated by serially deleted promoters,and the activity promoted by 680 nucleotides(nt)was the lowest.The region,which is 266 nt upstream of the ATG(initiation code),was effective for GUS expression.Meanwhile,the activity of the MdHB1 promoter MH 1057,which was stronger than MH(1057-266)and lack the 5′-untranslated region(5′-UTR),showed that5′-UTR may have a positive effect on gene transcription.3、The MdHB-1 promoter(1057 nt)activity in N.tabacum was positively induced by Ethrel and darkness,and it was suppressed by gibberellic acid(GA),whereas abscisic acid(ABA),salicylic acid(SA),wounding,and Pseudomonas syringae pv.tomato(DC3000)treatments revealed a slight auxo-action.4、Ethylene can positively regulated the ethylene-responsive element of the promoter and as the concentrations of the ethylene rose,the activity of GUS increased in the first stage,and then decreased.The 500 mg L-1 of ethylene had the maximum promotion for the ethylene-responsive element. |
