Molecular Mechanism Underlying The Effects Of Nitric Oxide On Photoperiod In Arabidopsis

Nitric oxide(NO)can delay plant flowering,but its mechanism of action is unclear.Light is one of the key environmental factors affecting plant growth and development.In addition to plant photosynthesis,an important signaling molecule can also be used to regulate plant growth and development.For example,the photoperiod pathway is also an important way to regulate plant flowering one.Whether nitric oxide interacts with the photoperiod pathway to regulate plant flowering is the starting point of this study.In this paper,the model organism Arabidopsis thaliana was used as the research object,and the biological clock Marker gene was fused with Luciferase(LUC)as the reporter gene for the study,and then the transcription activity of LUC was detected under continuous light conditions.Whether it affects the cycle,phase and amplitude of the biological rhythm to explain the mechanism of action of NO on the photoperiod pathway.The important marker genes in the photoperiod used in this paper are CCA1(Circadian clock associated 1),LHY(Late elongated hypocotyl 1),TOC1(Timing of cab expression 1),PRR7(Pseudo-response regulator 7),GI(Gigantean),By analyzing the transcriptional activity of these Marker genes under continuous white light to analyze the effect of NO on the plant photoperiod pathway.It was found that under white light,in nox1 mutants with increased endogenous NO content,PRR7 and GI were not affected,while the expressions of CCA1,LHY,and TOC1 were affected.It is speculated that the regulation of NO on the photoperiod pathway is mainly by affecting the core Oscillation of key gene expression is achieved.Further confirmed by q RT-PCR,under continuous white light conditions,nox1 mutants with high endogenous NO content also showed that the expression of the core clock control loop genes CCA1,LHY and TOC1 of the biological clock was significantly higher than that in WT The rhythm is the same as WT,and the expression in PRR7 is not affected.Studies have shown that the red light receptor PHYB can inhibit the flowering of plants in both long and short days,so it is speculated that under red light,NO will delay the photoperiod pathway of plant flowering.It was found that plant growth showed hypocotyl growth under red light.The exogenous application of NO exerted an inhibitory effect on the root growth of Arabidopsis thaliana cultured under red light,showing a dose-dependent trend.Statistical significance(P <0.001),but nox1 mutant with high endogenous NO was not affected compared with WT.For the number of rosette leaves and bolting time that affected flowering,it was found that with the increase of NO concentration,the bolting time and rosette leaf number both increased,and nox1 mutants with 100 ?M SNP and endogenous NO increased exogenously Compared with the wild type,the differences exhibited were statistically significant.Further experiments confirmed that the expression of central clock genes CCA1,LHY and TOC1 in the photoperiod pathway of Arabidopsis cultured under red light irradiation was still affected.Considering the confirmed effect of NO on the red light receptor PHYB,we speculate that the effect of NO on the photoperiod pathway may be through the influence of PHYB,and then transmit the signal to LHY,which affects the core clock oscillation and thus regulate the pathway to the photoperiod affects its downstream signal transduction,which further delays flowering.In conclusion,this study indicates that NO regulates the plant's circadian rhythm oscillations to regulate plant flowering.