Studies On Influence Of Endogenous Brassinosteroid On The Flowering-time And The Mechanism In Arabidopsis

Regulation of flowering time has been a focus of plant developmental biology and biology. As a transition phase from vegetative growth to reproductive growth, flowering time directly affect the crop growth period, the best time of crop pollination and seed development, so it is closely related to crop yield and quality. Research on flowering time is important to agricultural and horticultural production.The flowering transition is known to be regulated by numerous interacting endogenous and environmental cues. In Arabidopsis, the results of extensive genetic studies of late-flowering mutants revealed the existence of at least four signaling pathways that coordinately promote flowering, including environmental induction through photoperiod, temperature, autonomous floral initiation, and regulation by gibberellins (GAs). Additionally, some environmental factors, such as ambient temperature, light quality, light quantity, endogenous ascorbic acid and ethylene have also been found to be critical to mediate flowering. Although major components regulating flowering time have been identified in Arabidopsis, additional factors still await discovery.Brassinosteroids (BRs) are a class of steroidal hormones which has been found in many plant. BRs are essential for plant growth and development, including skotomorphogenesis, photomorphogenesis, xylem formation, cell division and cell elongation, which are now considered the sixth hormone in plant. In Arabidopsis, most BR-biosynthetic mutants and BR-insensitive mutants exhibit a prolonged vegetative phase and delay flowering time. This paper analysis BR action on the flowering time regulation make use of BR mutant and wild-type, the results as follows:1 Endogenous BR content of Arabidopsis affect flowering time. The results found that BR-deficient mutants det2 delay flowering time in LongDay(LD) and ShortDay(SD). Exogenous 24-epibrassinolide application could restore the flowering phenotype of det2. Exogenous 24-epibrassinolide application also could speed up growth and flowering time of wild-type Arabidopsis.2 Endogenous BR content of Arabidopsis had no Significant impact on photoperiodic pathway. Comparied transcription of key genes in the det2 with col, flowering integrates FT and SOC1 genes affected by the content of endogenous BR, other photoperiodic pathway genes transcription level were not significant changes.3 BR and PHYA together regulated growth and development of leaves. The content of endogenous BR affected the transcription level of PHYB, had no significant effect on PHYA, but exogenous 24-epibrassinolide application made phya significant change in the leaf phenotype.4 Floral induction was affected by Endogenous BR content of Arabidopsis was independent on vernalization pathway and autonomous pathway. Comparied transcription of key genes in the det2 with col, we found that the content of endogenous BR had slight impact on the transcription level of FLC in LD, had no significant effect on FLC in SD. FLC action on both vernalization pathway and autonomous pathway. Vernalization had no significant effect on flowering time of det2 and content of endogenous BR had only slight impact on the transcription level of FCA, which showed that content of endogenous BR had no significant effect on vernalization pathway and autonomous pathway.5 Endogenous BR content of Arabidopsis had no significant effect on GA pathway regulated flowering in non-induced short-day photoperiod, because exogenous GA3 application could restore flowering time of det2 in SD.6 Subcellular colocalization analysis showed that BR pathway downstream BZR1 with SVP localized in the nucleus.7 BR interact with SVP through BZR1.The emergence of fluorescent signal in BIFC showed that BZR1 interact with SVP. SVP was a connection point between BR and flowering time regulation network. Summing up the above results, it's indicated that endogenous BR content has no significant effect on the four major flowering pathway in Arabidopsis, BR may be a separate regulatory pathway of flowering time. In this study, the function of BR on flowering time regulation in Arabidopsis has been preliminary explored, which completed flowering time regulatory network and expanded the function of BR, as well as provided scientific basis and theoretical support for the mechanism of floral induction of plant developmental biology.