| Branches play an important role in the formation of plant morphology.Branches are developed from axillary buds.The growth and development of axillary buds is a very complex process,which is regulated by endogenous and exogenous factors.Tobacco(Nicotiana tabacum)is a scientific research model plant and a widely cultivated economic crop.The dormancy and germination of axillary buds and the growth and development of lateral branches will have a very important impact on the yield and quality of tobacco.To this end,this study applied different concentrations(1,10,and 50?mol·L-1)of the strigolactone analog GR24 solution to the leaf axils of tobacco plants after topping,and studied the effects of different concentrations of GR24solution on different sections of tobacco.The effects of the growth of axillary buds and lateral branches between positions and the regulation effects of antioxidant metabolism and carbon metabolism of axillary buds,lateral branches and corresponding leaves at different nodes,to analyze the position and concentration effects of strigolactone on the dormancy and bud growth of axillary buds.On this basis,RNA-Seq technology was used to analyze the transcriptomics analysis of the different developmental stages of tobacco axillary buds after topping and the effect of strigolactone on tobacco axillary buds,revealing the growth and development of tobacco axillary buds and strigolactone from the transcriptome perspective The molecular regulation mechanism affecting the growth of tobacco axillary buds is expected to provide a theoretical basis for the study of tobacco collateral development and collateral control pathways.The results of the study are as follows:(1)After treatment with 1 and 10?mol·L-1GR24 solution,the germination rate of tobacco axillary buds at nodes 1st to 6th was significantly lower than that of the control by24.44%?30.00%and 37.50%?44.00%,while the 50?mol·L-1GR24 solution treatment is not significantly different from the control.After strigolactone treatment,the length of the axillary buds of K326 and Yunyan 87 at 1st to 6th nodes was generally lower than that of the control.In K326 and Yunyan 87 axillary buds at nodes 1st to 3rd,the axillary buds were 50 and 1?mol·L-1respectively.GR24 has the best effect,and GR24 with 10 and 50?mol·L-1is the best in K326 and Yunyan 87 axillary buds at positions 4-6.After strigolactone treatment,the fresh weights of the 1st to 3rd nodes of tobacco axillary buds were also lower than those of the control.It can be seen that strigolactone has a certain inhibitory effect on the germination,elongation and fresh weight of tobacco axillary buds,and there is a concentration effect and a position effect.There are also certain differences in the effect of different varieties on the elongation of axillary buds.(2)The CAT activity of the lateral branches under different concentrations of strigolactone treatment increased to varying degrees,and increased 0.31 to 4.97 times in the 1st to 3rd nodes compared to the control.The PPO activities of the 3 nodes'lateral branches were all lower than the control.The PAL activity of the 3rd node lateral branch under the GR24 treatment of 10 and 50?mol·L-1was higher than that of the control,but the activities of POD and SOD were not significantly different from the control.The PPO activity of the leaves after strigolactone treatment was lower than that of the control as a whole.It can be seen that the strigolactone treatment increased the CAT activity of the collaterals,and inhibited the PPO activity of the collaterals and leaves to a certain extent.(3)Under the treatment of strigolactone,the content of sucrose,soluble sugar and fructose in the3rd lateral branches of tobacco and the activities of SPS and INV were all higher than those of the control,and at the same time increased the 1st node lateral branches'b-amylase activityand 2nd node lateral branches' ?-amylase activity.The content of starch,fructose,sucrose and soluble sugar in the 1st and 2nd nodes of the tobacco leaves after strigolactone treatment was lower than that of the control,but they were all higher than that of the lateral branches.It can be seen that strigolactone is beneficial to increase the content of lateral branches sugar and related enzyme activities at the 3rd node,and has a certain effect on regulating the source-sink transportation of lateral branches and leaves.(4)Transcriptome analysis based on different developmental stages of tobacco axillary buds and side branches showed that there were a total of 3355 differential gene expressions at 0 d and 2 d,a total of 6825 differential gene expressions at 0 d and 6 d,and a total of 5407 differential gene expressions at 2 d and 6 d.Among the 756 genes shared by the 3 comparison groups,6 genes related to antioxidant metabolism were screened,such as PER52,PRP1 and SODB,and 16 genes related to carbon metabolism,such as SS,SPS,SUS6,BAM7 and SWEET1 etc.GO enrichment analysis showed that the main biological processes and metabolic pathways that differentially expressed genes were enriched were:single-organism process,cells,and catalytic activity.Among them,the CK?0 vs CK?6 comparison group had the most enriched genes than the other comparison groups.Pathway is significantly enriched in pathways such as metabolic pathways,biosynthesis of secondary metabolites,and plant hormone signal transduction,among which the CRE1,AHP,B-ARR and A-ARR genes in zeatin synthesis are annotated in the plant hormone signal transduction pathway expression.In addition,the q RT-PCR test results also confirmed the reliability of the RNA-Seq analysis results.(5)Transcription analysis results of strigolactone-treated and untreated axillary buds and lateral branches showed that 332 and 1193 genes were identified in the CK?2 VS GR?2 and CK?6 VS GR?6 comparison groups,respectively.GO enrichment analysis showed that most of the differential genes were enriched in cellular process,single-organism process,metabolic processes and biological regulation pathways.Pathway is significantly enriched in endoplasmic reticulum protein processing in endoplasmic reticulum,diterpenoid biosynthesis,metabolic pathways,and biosynthesis of secondary metabolites pathways.On the 2nd day of treatment,the expression of GA2OX2 and zeatin biosynthesis-related genes related to gibberellin and ZOX1 were down-regulated compared with the control.Further analysis of the expression of strigolactone related genes revealed that the genes related to strigolactone synthesis in tobacco axillary buds and side branches are CCD7 and D27,and the genes related to strigolactone signal transduction are MAX2,D14,DAD2 and SMAX1,and exogenous strigolactone treatment for 6 days,can promote the expression of SMAX1,D14,DAD2,CCD7 and D27 genes in the bud. |
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