Effect Of Exogenous Reactive Oxygen Species On Flower Bud Differentiation In Tobacco

There are many factors influencing the plant flowering transition, which is a research focus.This study explored the mechanism of flower differentiation,explored whether ROS can regulate plant flower development as signal molecules from the perspective of reactive oxygen species.A pot experiment, by spraying exogenous methyl viologen and exogenous H2_O2 to simulate the source of O2·- and H2_O2 respectively,was carried out to explore active oxygen metabolism and tobacco flower bud differentiation on physiological and molecular level. The results showed that:（1）The exogenous methyl viologen made O2·- and H2_O2 rise rapidly in tobacco, and activated the ASA and GSH circulation in tobacco at the same time.Meanwhile, antioxidant ASA and GSH content and the activity of protective enzyme APX and GR had different degree of ascension,which effectively removed reactive oxygen species.The 5 d,10 d treatment of spraying exogenous methyl viologen significantly increased reactive oxygen content, and after spraying, the active oxygen was effectively removed, then returned to normal level;The 20 d and 25 d treatment of spraying exogenous methyl violet leaded to a substantial accumulation of active oxygen content in tobacco, reduce of ASA-GSH circulation system activity, and a higher level of active oxygen content in tobacco.（2）Exogenous methyl viologen treatment to a certain extent changed the flower development in gene expression, the budding leaf number and development process of flower bud.The 5d and 10d treatment significantly inhibited the expression of flowering suppressor FLC, but promoted the expression of flower development genes LFY, at the same time leaded to budding leaf number significantly reduce,and promoted flower bud differentiation. This proved that 5 d and 10 d treatment of exogenous methyl viologen （5 umol/L） and only by increasing active oxygen content in a certain period of time could lead to the change in the direction of stem tip developmentAnd a high level of active oxygen for a long time was bad for development of flower.The signal pathways between ROS signals and flowering gene FLC, FT, LFY, SOC still expects more study.（3）The influence of exogenous H2_O2 and exogenous methyl viologen treatment had same effects on active oxygen metabolism in tobacco. Exogenous H2_O2 caused rapid increasing of H2_O2, and activated the ASA-GSH system at the same time,which can effectively remove ROS.The 5d, 10d treatment significantly elevated the content of active oxygen, which caused antioxidant ASA-GSH system positively and effectively to remove active oxygen;the longer time of spraying H2_O2, the higher content of O2 and H2_O2, the more serious oxidative damage,and the worse removal ability of ASA and GSH cycle. Similarly to methyl viologen treatment,20 d and 25 d treatment of H2_O2 leaded to a higher level of active oxygen content in tobacco,high concentration of active oxygen had disadvantages to flowering transition.（4）Exogenous H2_O2 treatment promoted the expression of flowering gene,flower development process and budding in different degrees.It was similar to exogenous methyl viologen processing, the effect of 5 d and 10 d treatment was remarkable,which proved that when under the processing of 5d-10d of exogenous H2_O2 （10 mmol/L）, a high content of active oxygen in a certain period of time could promote flower development.