The Impact Of Sucrose Transporter OsSUT5 On Low Phosphate Adaption In Rice(Oryza Sativa L.)

Phosphorous is a macronutrient that is essential for plant growth and development, which has important biological function in the process of life activity. Despite the phosphorus content in soil is rich, the available phosphorus is easily fixed in forms that are difficult to be absorbed by plant. Plant phosphorus deficiency phenomenon is widespread. Recently, more and more attention has been focused on the sucrose acted as a signal molecule in plant metabolism network, the function of sucrose in low phosphorus reaction was newly discovered. Sugar transporters SUTs are responsible for sugar transport and distribution in plant. In this paper, we used two transgenic indica rice lines (SUT5-9 and Anti-SUT5-11) and wild type rice Minghui86 (WT) as the experimental materals to investigate the OsSUT5 roles in the effect of low phosphorus stress adaption in rice, through observing the transgenic rice agronomic traits of whole growth period, detecting physiological and biochemical changes associated with phosphorus metabolism, and making molecular detection of related phosphorus absorption and transport in low phosphorus stress. The results are summarized as follows:1. The over-expression of OsSUT5 promoted the SUT5-9 vegetative and reproductive growth under low phosphorus stress, which resulted in the yield per plant 17.3% higher than that of WT. While the repressed-expression of OsSUT5 had an inhibiting effect on the vegetative and reproductive growth of Anti-SUT5-11 under low phosphorus stress, which resulted in the yield per plant 38.7% lower than that of WT.2. In the vegetative growth stage, when the phosphorus stress was slight (seedling stage), the relative phosphorus utilization of the SUT5-9 was 17.4% lower than that of WT. When phosphorus stress increased to a certain extent (tillering stage), the relative phosphorus accumulation of the SUT5-9 was 38.2% higher than that of WT. While the relative phosphorus accumulation of the Anti-SUT5-11 had no significant difference compared with that of WT in seedling stage, but 42.9% lower than that of WT in tillering stage. The relative phosphorus efficiency of Anti-SUT5-11 had no significant difference compared with that of WT at seedling stage and tillering stage.In the reproductive stage, the relative phosphorus accumulation of the SUT5-9 was 35.8% higher than that of WT, while repressed-expression of OsSUT5 had no significant difference of relative phosphorous accumulation compared with that of WT.3. When the phosphorus stress was slight (seedling stage), the over-expression of OsSUT5 promoted the recycling of phosphorus via improving the SUT5-9 internal acid phosphatase activity, when phosphorus stress increased to a certain extent (tillering stage), the over-expression of OsSUT5 had no significant effect on the SUT5-9 internal acid phosphatase activity.4. In the vegetative growth stage, the over-expression of OsSUT5 promoted the carbohydrates formation and distribution to the root of SUT5-9 under low phosphorus stress, while repressed-expression of OsSUT5 reduced the Anti-SUT5-11 carbohydrate formation; In the reproductive stage, the over-expression of OsSUT5 made the SUT5-9 transport more carbohydrate to the panicle, while repressed-expression of OsSUT5 made the Anti-SUT5-11 accumulate more carbohydrate in the stem, leaf and root.5. The sword leaf photosynthetic rate detection showed that the SUT5-9 improved the sword leaf photosynthetic rate under low phosphorus condition, while repressed-expression of OsSUT5 reduced the Anti-SUT5-11 photosynthetic rate.6. Phosphate and sugar transport genes expression in the tillering stage under low phosphorus condition showed that a number of OsPTs genes expression in leaf and root of the SUT5-9 were significantly higher than that of WT, while OsPT1, OsPT6-8 genes expression in leaf of Anti-SUT5-11 were lower than that of WT. The OsSUT1, OsSUT2 and OsSUT4 genes expression in SUT5-9 were higher than that of WT, while the expression of OsSUT1, OsSUT2 and OsSUT4 genes expression in Anti-SUT5-11 were not lower than that of WT.Based on the results, in the vegetative growth stage, when the phosphorus stress was slight, the over-expression of OsSUT5 promoted the recycling of phosphorus via improving plant internal acid phosphatase activity. When phosphorus stress increased to a certain dgree, the over-expression of OsSUT5 promoted the ability of phosphorus absoption via thansfering more carbohydrate to root which improve the root biomass to expand the contact surface of soil and increasing the expression of numbers of OsPTs. While repressed-expression of OsSUT5 decreased the synthesis of carbohydrates, and reduced the absorption of phosphorus. In the reproductive growth stage, the overexpression of OsSUT5 increased the accumulation of phosphorus, photosynthetic rate of plant and the transhipment of sugar to the panicle of the grain, which improved the yield of rice. While repressed-expression of OsSUT5 led to the decrease in phosphorus accumulation, photosynthetic rate of plant and capacity of transporting sugar and phosphorus to the panicle of the grain, thereby resulting in the decrease in output.