Study On The Molecular Mechanism Of BpmiR156/BpSPL16 Affecting Adventitious Root Of Betula

miR156 regulates plant growth and development by acting on its target genes SPLs.In this study,BpmiR156 overexpression(OE156)transgenic Betula were used as the material to explore the rooting ability of tenderwood cuttings of the OE156 lines,and to monitor the physiological and gene expression changes of adventitious roots.According to the transcriptome data of adventitious roots and 5’RACE,the target gene of BpmiR156 regulating adventitious root formation was determined,and the influence of BpSPL16 on the formation of adventitious roots was analyzed on the basis of obtaining BpSPL16 suppressed expression birch lines.The results are as follows:1.Taking the twigs of the current year for cutting rooting,it was found that without any exogenous hormone treatment,the cutting rooting rates of the OE156 lines were significantly higher than that of WT line,reaching 86.74%.Each cutting produced more adventitious roots,shorter lengths of adventitious roots,and more secondary lateral roots.2.Through the paraffin section and the detection of the physiological changes of the adventitious root formation process,it was found that the adventitious roots of the OE156 lines originated from the cambium of the stem;The changes of IAA,zeatin,ABA and JA contents in adventitious roots were the highest at 9 days after cutting.There were differences in the content of NO,H2O2,soluble sugar,soluble protein,cat and pod between OE156 and WT during adventitious root development.3.Using the stem segment at the lower end 1 cm birch cuttings at 0,3,6,9,12,15,18,21d as materials,the gene expressions during rooting process were analyzed by transcriptome,and the results showed that the gene expression of OE156 at each time point was significantly different from that at 0 d,especially between 0 d and 3 d.The number of differentially expressed genes at each time point during the adventitious root formation of OE156 birch line was between 3925-4879,among which the up-regulated expression gene was 2115-2348,and the down-regulated expression gene was between 1756-2612;the number of differential genes in the 0 d VS All group comparison group is 2524.Through KEGG enrichment analysis,it was found that 0d VS All group differential genes were mainly enriched in plant hormone signal transduction,metabolic pathways of starch and sucrose metabolism,phenylpropane metabolism,and plant pathogen interactions.4.The target gene BpSPL16 of BpmiR156 regulating adventitious root formation was determined by transcriptome data and 5’RACE technology.After the BpmiR156 cleavage site of BpSPL16 was mutated,a pGWB111-BpSPL16-SRDX suppression expression plant vector was constructed,and 5 BpSPL16 suppression expression lines were obtained(RE 16-1～5).5.The rooting rate of softwood cuttings of the RE 16 lines was determined and growing status.The results showed that the adventitious rooting ability of the RE 16-1～5 liness were higher than that of WT.Among them,the rooting rate of the RE 16-3 cuttings was the highest,which was 60%.Compared with WT,the RE 16 lines had no significant changes in seedling height and ground diameter,while the pitch of the nodes of the RE 16 lines was significantly shorter than that of the WT line.