Study On Effects Of Exogenous Auxin On Fructose Metabolism In Tomato Fruits

Fructose is a product of sucrose hydrolysis. Its metabolism is related to fruit flavor and quality in plant. Therefore, the study on fructose metabolism of plant fruit possesses important significance and value for regulation on fruit fructose metabolism and controlling the ratio of fructose in ripe tomato fruit. At present, the study on metabolism of fructose is still at a preliminary stage, which concentrated on soluble sugar content and accumulation, activity of sucrose-metabolizing enzymes, route of fructose into fruit, expression of sucrose-metabolizing enzymes gene and so on. But the reports were rarely about the change in the temporal and spatial expressions of fructose metabolism, especially about effects on the temporal and spatial expression of fructose metabolism by various exogenous factors. And these aspects are the groundwork to regulate fructose metabolism in plant fruits and control the fruit sweetness and quality. Therefore, the profound study is necessary.Tomato(Solanum lycopersicum cv. Liaoyuanduoli) were cultivated in greenhouse in older to take samples compared with natural tomato fruit after PCPA and 2,4-D treatment which was wildly employed on production in this study. The tissue anatomical technique,gene cloning technique, gel eleetrophoresis technique, real-time fluorescent quantitative PCR technique, modern analysis-testing techniques and bioinformatics software were employed to investigate the effects on sugar composition and content, starch content,activities of sucrose-metabolizing enzymes and fructokinase, gene expression of fructokinase in cultivars tomato and different parts of cultivars tomato fruits during development by exogenous auxin treatment at flower stage. Effects on fructose metabolism were studied systematically for the first time during tomato fruits development by exogenous auxin treatment at physiological, molecular and protein levels. It was clear about sugar composition and content, activities of sucrose-metabolizing enzymes and fructokinase, gene expression of fructokinase in different parts of tomato fruits during development. The intention of this study is in order to establish basic theory for further study on tomato sucrose metabolism and regulation of sugar accumulation by plant growth regulator. The main results are as follows.1. It was found that effects of PCPA and 2,4-D treatment on growth and development of cultivars tomato fruits. Growth and enlargement of Liaoyuan duoli tomato fruits were distinctly accelerated by dipping flowers using PCPA and 2,4-D, especially efficiency was significant by 2,4-D treatment.2. Further verification was obtained that glucose and fructose were the predominant sugars in Liaoyuanduoli tomato at the mature stage during fruits development. Accumulating hexose was the sink pattern of Liaoyuan duoli tomato. The original sink type of accumulating sugar in fruits weren't changed by PCPA and 2,4-D treatment. And fructose and glucose accumulation were increased during fruits mature stage of cultivars tomato.3. Effect on starch content in different development stages of tomato fruits was different by PCPA and 2,4-D treatment. The starch content was increased during fruits mid stages of Liaoyualaduoli tomato by PCPA and 2,4-D treatment.4. Effects on activities of sucrose-metabolizing enzymes and fructokinase in cultivars tomato during fruits development. The invertase activity wasn't affected at the early stage of Liaoyuanduoli tomato fruits by PCPA and 2,4-D treatment, but the invertase activity was increased at the mature stage of tomato during fruits development; fructokinase activity reduced at the ripe tomato fruits by PCPA and 2,4-D treatment. But the activities of sucrose synthase and sucrose phosphate synthase in cultivars tomato fruits weren't affected by PCPA and 2,4-D treatment. And the activity of sucrose phosphate synthase was low in cultivars tomato fruits.5. In order to detect FRK gene expression during the development of tomato fruit, we cloned three genes in fructokinase gene family LeFRK1, LeFRK2 and LeFRK3 as the basis for future work.6. It was clear that effect of PCPA and 2,4-D treatment on gene-FRK1, FRK2 expression in different parts of cultivars tomato during fruits development. FRK1 and FRK2 gene expression were ascended firstly then descended both treatment and control groups during fruits development. Activity of fructokinase presnetd the lowest level, but FRK1 gene expression showed a higher level during fruit ripening, and gene expression of fructokinase was accelerated during mature period of fruit after PCPA and 2,4-D treatment.7. In summary, fructose metabolism of cultivars tomato might be regulated at a certain extent by PCPA and 2,4-D treatment, which were exogenous auxin matter. This regulation for metabolism was mainly implemented through controlling the soluble acid invertase and fructokinase. And its core was regulation of gene expression of fructokinase. This regulation for fructose metabolism might be the one of important factors to enhance quality of tomato fruit. Thereby, the important factors for quick fruit enlargement were that sucrose was rapidly decompounded in cell vacuole and fructose was slowly decompounded. The PCPA and 2,4-D of exogenous auxin might promote this process leading to improve fruit enlargement. At the meantime, exogenous could improve quality of tomato fruit.