A Research Of Red Light And Far-red Light On Tomato Growth And Flowering- Related Genes

To elucidate the effect of light environment controlled by red and far-red light on tomato plants, with tomato as the material, the stem height, stem diameter, time to flowering, fresh and dry weight, cholorophyll content, photosynthesis, hormone content and mineral element content were measured. To demostrate the mechanism of tomato flowering which effected by light environment controlled by red and far-red light, tomato FT-like genes were cloned and its function was analysised in tomato plants, meanwhile, the expressions of FT-like genes in different light conditions were measured. As the phytochromes are main red and far-red light photoreceptors, the effect of phytochromes on tomato flowering and FT-like genes expression was further studied. Based on these results, the mechanisms of tomato flowering controlled by light environment were elucidated. The main results are described as follows:1. After end-of-day far-red light treatment for 10 min, the plant height and stem fresh weight changed significantly, with the increasing of far-red light intensity, the plant height and stem fresh weight increased. When the far-red light intensity reached 10μmol/m2/s, the plant height and stem dry weight reached their maximum value. After 10 min’s end-of-day far-red light with the intensity of 10μmol/m2/s treatment, the content of IAA and GA3 increased significantly, while the content of chlorophyll and photosynthesis decreased, also, the content of N in stem decreased but the content of P and K increased, meanwhile, the content of N and P in leaf decreased while the content of K of leaf increased, and the N, P, K contents of tomato seedling in root increased. Therefore, the plant height and growth of tomato seedling can be controled by the end-of-day far-red light intensity.2. Results showed that, with the increasing with of night break time, the stem diameter and time to flowering increased while the stem height and the content of IAA and GA3 decreased, however, the per fruit fresh mass of first spica increased. When the night break was 5 times, which meaned night break of every 2 hours, the stem height, stem diameter, time to flowering, the content of IAA and GA3 and the per fresh fruit mass of first spica were the same as the night break by constant red light. Therefore, the growth and flowering of tomato plants can be controlled the times of night break in night.3. 13 PEBP(phosphatidylethanolamine binding protein) genes were uncovered by Analysis of the tomato genome and six of which were FT-like genes named as SlSP3 D, SlSP6 A, SlSP5 G, SlSP5G1, SlSP5G2 and SlSP5G3. The 6 FT-like genes were analyzed to clarify their functional roles in flowering using transgenic and expression analyses.It showed that the SlSP5 G, SlSP5G2 and SlSP5G3 proteins were floral inhibitors whereas only SlSP3D/SFT(SINGLE FLOWER TRUSS) was a floral inducer. SlSP5 G was expressed at higher levels in long day(LD) conditions compared to short day(SD) conditions while SlSP5G2 and SlSP5G3 showed the opposite expression pattern. The silencing of SlSP5 G by VIGS(Virus induced gene silencing) resulted in flowering early under LD conditions in tomato plants while the silencing of SlSP5G2 and SlSP5G3 led to early flowering under SD conditions. The higher expression levels of SlSP5 G under LD conditions were not saw in phyB1 mutants, while the expression levels of were increased in phyB1 mutants under both SD and LD conditions compared with wild type plants. These data suggested that SlSP5 G, SlSP5G2 and SlSP5G3 are controlled by photoperiod, and the different expression patterns of FT-like genes under different photoperiod may contribute to tomato being a day neutral plant. In addition, PHYB1 mediates the expression of SlSP5 G, SlSP5G2 and SlSP5G3 to regulate flowering in tomato.4. Under low red: far-red light ratio, the flowering of wild type tomato and phyB1 mutant were inhibited. Also, night break by red light inhibite tomto flowering, however, it had no influence on tomato phyB1 mutant. In wild type tomato plant, low red: far-red ratio promoted the expression of SlSP5 G, and night broke by red light had the same effect. In phyB1 mutant, the expression of SlSP5 G always was very low, but the expression of SlSP3 D was higher under low red: far ratio condition. The expression of SlSP5 G,SlSP5G2 and SlSP5G3 were higher in tomato phyB1 mutant and they were stable under various light conditions.