The Study Of Nitrogen Nutrition Regulation Of Flowering Induction Related Gene Experssion In Arabidopsis Thaliana

The time of flowering is crucial for plant reproductive success. In recent years, it has been proposed that there are four main pathways to control the plant flowering time in model plant Arabidopsis thaliana: photoperiod pathway, vernalization pathway, autonomous pathway and Gapathway. Besides its own genetic factors, Plants blossom induction can also be affected by other environmental factors, such as external nutrition conditions and water condition. Nitrogen (N) is an essential nutrient element which is required for plant growth. Can it eventually influence flowering time through regulating flowering time genes transcription level? So far, such investigation has not been reported. Therefore, in this study, we use real-time PCR to analyze the expression levels of main flowering induction related gene CO, FLC, SOC1 and FT under different nitrogen levels and nitrogen forms supply in model plant Arabidopisis thaliana to reveal the molecular mechanism of nitrogen nutrition regulation flowering induction. The main results are as following:(1) A vermiculite incubation experiment was conducted to study the influence of different nitrogen levels on flowering induction related gene expression in Arabidopsis, using 4.25 mM nitrate as control treatment, 0.425 mM nitrate as low N treatment and 8.5 mM nitrate as high N treatment. Results showed that flowering time in low N treatment was significantly later than that in normal and high N treatment. Consequently, we analyzed expression of flowering induction related gene in Arabidopsis. Contrast with low N treatment, in normal N treatment, the expression of CO was significantly higher; the expression of FLC gene was significantly lower; the expression of SOCl and FT were significantly higher. It indicates that low nitrogen stress could suppress the expression of CO which is a key component in photoperiod pathway, while could promote the expressing of FLC in autonomy pathways. Eventually, the flowering integrative effect gene SOCl and FT were inhibited by low nitrogen stress, which directly caused delayed flowering.(2)A vermiculite incubation experiment was conducted to study the influence of different nitrogen forms on flowering related gene expression in Arabidopsis, using 100% nitrate,50% nitrate+50% ammonium and 100% anmonium as three treatments with 4.25 mmol/L N. Results showed that Arabidopsis flowered firstly in nitrate treatment, while flowered latestly in ammonium treatment. Consistent with it, expression of flowering induction related gene varied among the three treatments. In nitrate treatment, the expression of CO was significantly higher than that in ammonium treatment; the expression of SOCl was the lowest in ammonium treatment, and was the highest in nitrate treatment. Moreover, in ammonium nitrate treatment, the expression of SOCl was between nitrate and ammonium nitrogen. However, there was no difference of FT expression among the three treatments. It suggests that ammonium could also suppress CO and only inhibit one flowering integrative effect gene SOCl but not FT, which finally leaded to delayed flowering.