The Study On Phosphorus Nutrition Characteristics Of Transgenic TsVP Coton

There are various metal ions such as Ca2+、Al3+、Fe2+ in soil,which can form insoluble phosphate with phosphate ion and can not be directly absorbed and utilized by cotton.The lack of available phosphorus in soil has become an important factor affecting the increase of cotton yield.The TsVP gene was cloned from Thellungiella salsuginea in laboratory.The protein encoded by TsVP gene was vacuole hydrogen ion pyrophosphatase(Vacuolar H+-PPase).It can pump H from intracellular vacuole into plant vacuole by hydrolyzing PPi of cell metabolism,thus maintaining vacuole and intracellular H+ gradient.In this work,the phosphorus nutrition characteristics of transgenic TsVP cotton and wild type Lumianyan 21 under low phosphorus stress were studied by using sand culture,hydroponics and soil culture with Ts VP transgenic cotton T8-3,T18-3,T18-8 as materials.To explore the application potential of transgenic TsVP cotton in low phosphorus tolerance breeding.In the sand culture experiment,transgenic cotton T8-3,T18-3,T18-8 and wild type Lumianyan 21 were seeded in enough phosphorus(123.88 mg/kg),low phosphorus(12.38 mg/kg)and Al-P(AlPO4),Ca-P(Ca3(PO4)2),Fe-P(FePO4 4H2O),treated sand respectively,enough phosphorus was treated with complete Hoagland nutrient solution once a day,and low phosphorus and other phosphorus source treatments were used to remove phosphorus.The photosynthetic and chlorophyll fluorescence parameters,inorganic phosphorus,sucrose and starch contents of the fifth fully spreading leaves of each strain were measured when the plants grew to the five-leaf and one-center stage.The plant height of cotton in four leaf stage,five leaf stage and six leaf stage was counted,and the leaf area was calculated.The phosphorus content and biomass of each plant were measured and the root-shoot ratio was calculated.The results of sand culture test showed that the phosphorus content,root-shoot ratio,net photosynthetic rate and biomass of transgenic TsVP cotton were significantly higher than those of wild type control under insoluble phosphorus treatment.The ability of activating and utilizing insoluble phosphorus in transgenic Ts VP cotton was significantly higher than that in wild type control.Transgenic cotton had better ability to activate and absorb insoluble phosphorus,which provided more phosphorus for cotton growth and improved the growth status of cotton.In the hydroponic experiment,transgenic TsVP transgenic cotton T8-3.T18-3,T18-8 and control Lumianyan 21 were divided into two groups at sufficient phosphorus(1000 μmol/L KH2PO4)nutrition solution when they grew to four leaves and one heart stage,and were divided into two groups at sufficient phosphorus(1000μmol/L KH2PO4),respectively.Under the condition of low phosphorus(5 μmol/L KH2PO4),the root morphology,net photosynthetic rate,pH,root tip auxin content,plant phosphorus content and biomass of cotton were measured.The results of hydroponics showed that transgenic cotton could secrete more protons than wild type under low phosphorus treatment,and transgenic TsVP cotton had stronger root acidizing ability,root-shoot ratio,lateral root number and total root length of transgenic cotton.The root surface area of TsVP cotton was also significantly higher than that of wild type,and the root growth of transgenic cotton was more developed.In the soil culture experiment,transgenic cotton T8-3,T18-3,T18-8 and L21,respectively in the enough phosphorus(available phosphorus greater than 10 mg/kg)and low phosphorus(available phosphorus for 4.32 mg/kg)soil growth.The net photosynthetic rate and Fv/Fm of the whole leaves of cotton were determined by the growth of the plant to four leaves,and the agronomic traits such as seed cotton yield were determined by the plant ripening period.The soil culture experiment showed that the TsVP cotton had better net photosynthetic rate and Fv/Fm than the wild type under the condition of low phosphorus,and the plant height,the number of fruit branches and the yield of seed cotton were also significantly higher than that of wild type.In low phosphorus soil,the TsVP cotton has higher photosynthetic efficiency and seed cotton yield.The results showed that the improvement of the ability of transgenic cotton to utilize insoluble phosphorus was due to the ability of transgenic cotton roots to secrete more protons,to increase the level of rhizosphere acidizing,and to absorb more phosphorus from insoluble phosphate.Compared with wild type,transgenic TsVP cotton had better photosynthetic efficiency and PSII performance,and transgenic TsVP cotton could accumulate more biomass and seed cotton yield.In addition,TsVP cotton has more developed roots than wild type,which increases the contact area between roots and soil,and improves the ability to absorb phosphorus from the environment.Therefore,the overexpression of TsVP gene significantly improved the tolerance of cotton to low phosphorus stress,and provided excellent candidate genes and germplasm resources for cotton breeding with low phosphorus tolerance.