Expression Analysis Of The Gene In Tobacco BR Signaling Pathway And Flower-related In Flower Bud Differentiation In Response To Low Temperature In Seedling Stage

Tobacco(Nicotiana tabacum L.)seedlings are prone to early flowering due to sustained low temperature stress,which leads to a decrease in the number of effective leaves of tobacco,not only affects the growth of tobacco,but also affects its yield and quality.It is particularly urgent to explore themolecular mechanism of early flowering caused by low temperature in seedling stage.In this study,from the perspective of two biological pathways,the BR signal transduction pathway and flower development,the BR signal transduction pathway and flower development-related genes were used as entry points to detect the development of shoot tip dynamics and related genes in stems.The relative expression of the tip was used to investigate the effects of low temperature treatment on the flower bud differentiation time and bud time of the plant and the specific molecular mechanism.The main findings are as follows: 1.GO annotation analysis and BINGO enrichment analysis Annotation analysis of GO function and analysis of BINGO enrichment between genes associated with brassinosteroid signal transduction pathway and genes associated with flowering.A significant correlation was found between the BR signal transduction pathway and flower development-related genes.The enrichment results of the BR signal transduction pathway and flower development-related biological pathways all point to the BRI1 and SVP genes.The SVP gene may play a key role in communicating the pathway of BR signaling and flower development.2.Effects of low temperature at seedling stage on flower bud differentiation and bud stage The flue-cured tobacco materials Zunyan No.6 and LM4 with different flowering bud differentiation in response to low temperature sensitivity in seedling stage were used to observe the dynamic flower bud differentiation process of shoot tip meristems after seedling stage low temperature induction treatment and normal temperature control.The results show: the low temperature treatment of Zunyan No.6 and LM4 at 12 ° C for 10 days allowed the start of flower bud differentiation to start 5 days and 3 days in 6 leaf stages.At the same time,the whole stage of stem tip bud differentiation of Zunyan No.6 and LM4 was delayed by 4 days and 2 days,respectively.The flowering time from the bud stage to the center of the plant was delayed 4 days and 1 day respectively.The effective leaf number of Zunyan No.6 and LM4 low temperature treated plants was 6.8 and 2.8 leaves less than the normal temperature control plants,respectively.The low temperature at seedling stage promoted the initiation of flower bud differentiation of Zunyan No.6 and LM4,and the number of leaf primordia and leaves decreased,but the flower bud differentiation process of Zunyan No.6 and LM4 slowed down,and then the reproductive growth process slowed down,and even the buds The opening period of the period and the center flower is delayed.It indicated that the flowering and inflorescence development time of low temperature treated tobacco plants might be delayed compared with normal temperature treatment.The low temperature in the seedling stage would hinder the flower development process and prolong the reproductive growth process.The initial induction of flower bud differentiation of Zunyan No.6 was more sensitive than that of LM4.The number of low temperature treated Zunyan No.6 was higher than that of LM4.3.Effects of low temperature at seedling stage on expression of related genes during flower bud differentiation Quantitative analysis of NtBRI1,NtBSK3,NtSVP and NtFLC genes in flower bud differentiation stage under different temperature treatment conditions with Zunyan No.6 and LM4 indicated that the up-regulation of NtBRI1 and NtBSK3 gene expression may be up-regulated with NtSVP gene.There is a direct relationship.At the same time,the activation of BR signal may be directly related to the development of delayed flower tip differentiation stage.There is a certain correlation between the low temperature induction and the BR signaling pathway in the response of flower bud differentiation in common tobacco.The low temperature in the seedling stage will enhance the BR signaling pathway,which may reduce the expression of NtSVP and NtFLC,thus reducing the initiation of the two genes on flower bud differentiation.Inhibition,thereby inducing flower bud differentiation in advance.The sensitivity of flower bud differentiation in response to low temperature induction in seedling stage was related to the enhancement of NtBRI1,NtBSK3 expression,and the reduction of NtSVP and NtFLC.4.Effect of BR signal transduction pathway on the expression of genes involved in flowering The effects of BR signal on the expression of NtSVP and NtFLC were investigated by spraying exogenous BR hormones on the 6-leaf stage of Zunyan 6 and LM4.Within 3 hours to 15 hours of exogenous BR hormone spraying,the genes NtBRI1,NtBSK3 and NtSVP showed a trend of up-regulation.The NtBRI1 and NtBSK3 simultaneously responded to the stimulation of BR hormone,and reached the peak of expression at the same time,while the peak of NtSVP gene expression was later than the peak of NtBRI1 and NtBSK3,which was delayed by 3 hours.This indicates that there may be a synergistic relationship between NtBRI1,NtBSK3 and NtSVP in time.There is also the possibility that the NtSVP functions downstream of BR signaling.Zunyan No.6 responded to exogenous BR hormone faster than LM4.LM4 and Zunyan 6 had the same response rate of the gene NtSVP after exogenous BR hormone stimulation.In addition,the NtFLC in the shoot tips of the two materials showed a significant up-regulation at the 33 rd hour of exogenous BR hormone spraying.It indicated that the stimulation of exogenous BR hormone may directly affect the expression level of NtFLC in the shoot tip of plants,and it is a positive correlation.It is speculated that the activation of BR signaling in the shoot tip of plants may be responsible for the up-regulation of NtSVP and NtFLC expression.There is temporal synergy between BR signal-related genes(NtBRI1,NtBSK3)and NtSVP and NtFLC gene expression.The NtSVP may have a "bridge" effect between the BR signal and the NtFLC,which affects the developmental process of vegetative growth and reproductive growth.