Charaterization Of Chrysanthemum Phosphate Transporter CmPht1;2

Chrysanthemum morifolium Ramat.is one of the top ten famous traditional flowers in China and one of the four largest cut flowers in the world.Chrysanthemum is widely cultivated throughout China due to its wide useage,high ornamental and economic values.Phosphorus is one of the indispensable nutrient elements in the growth process of chrysanthemum.The lack of phosphorus affects the growth state of chrysanthemum and its secondary metabolism process,which affects its development of lateral branches and lateral buds,thus reducing its ornamental value.The efficiency of phosphorus uptake by plants from soil is one of the main limiting factors for plant yield.Therefore,it is necessary to explore the genes enable plants having high phosphorus utilization efficiency and low phosphorus tolerance.The phosphate transporter gene CmPht1;2 was cloned from the low phosphorus tolerance chrysanthemum’Nannongyinshan’.The study on the mutants of CmPht1;2post-translationally modified amino acid sites found that G84A,G222A,T239A,Y242A,and N422A of the Cmphts yeast transformants couldn’t grow well in low phosphorus condition and were all out of the normal Michaelis-Menten equation,indicating that these sites are criticle for phosphate uptake of CmPht1;2.The effect of these modification sites on the phosphate transport function of CmPht1;2 in plants needs to be further verified.Chrysanthemum is a polyploid plant,due to the influence of endogenous normal CmPht1;2protein,it is difficult to directly compare the effects of these mutants on the phosphate transport function of CmPht1;2.Rice is phosphorus uptake,transport,and signal pathways research model material,and which is relatively easy to genetic transformation.We generated CmPht1;2 transgenic rice plants in’Wuyunjing 7’genetic background.The function of CmPht1;2 and its effect on rice growth and development was identified by charaterizting the phosphate absorption capacity and agronomic traits of transgenic plants.Transgenic plants of CmPht1;2 mutants with post-translational modification sites G84A,G222a,T239A,Y242a and N422A was analyzed to explore their effects on CmPht1;2phosphate absorption function in rice.The main research results are as follows,1.In this study,expression vector was constructed to transfer Chrysanthemum phosphate transporter gene CmPht1;2 and and its post-translational amino acid modification site mutation CmPht1;2^G84A、CmPht1;2^G222A、CmPht1;2^T239A、CmPht1;2^Y242A、CmPht1;2^N422Ainto rice’Wuyunjing 7’.A total of positive plants CmPht1;2-OE 45 strains,G84A 41 strains,G222A 36 strains,T239A 37 strains,Y242A 39 strains,and N422A 37 strains were obtained.2.The statistical analysis of the seedling phenotype and maturity phenotype of CmPht1;2-OE T₂material showed that the plant height,biomass,effective panicle numbers,branch numbers and yield of CmPht1;2-OE material were higher than those in the wild.CmPht1;2 may promote the absorption of phosphate in CmPht1;2-OE materials.The phenotype of Cmphts-OE material at maturity stage was counted.The plant height and effective panicle numbers of Cmphts-OE material were lower than that of CmPht1;2-OE material.Mutations at different amino acid modification sites may affect the function of CmPht1;2.3.RT-PCR was used to detect the expression levels of CmPht1;2 and Os SPX2,Os IPS1,Os PT2,Os PT3,Os PT6,Os PT8,Os PT10,which were known to be related to phosphorus absorption and utilization in rice.Under low phosphorus conditions,the phosphorus starvation response genes in CmPht1;2-OE materials are inhibited at the transcription level,and the degree of inhibition has a certain correlation with the expression level of CmPht1;2.Chrysanthemum phosphate transporter CmPht1;2 can replace phosphate transporter of rice to perform the phosphate transport function to a certain extent.Compared with the wild type,CmPht1;2-OE material is less sensitive to low-phosphorus stress and may have better adaptability to low-phosphorus conditions.The expression patterns of phosphorus-related genes in T239A,Y242A and N422A materials under low phosphorus conditions are different from those of CmPht1;2-OE materials,these three sites may play an important role in the function of CmPht1;2.4.The effective phosphorus content of the CmPht1;2-OE materials were determined.The root phosphorus content of the CmPht1;2-OE materials were higher than that of the wild-type materials under both normal phosphorus and low phosphorus conditions.CmPht1;2 has the function of promoting the absorption of phosphate.This study lays the foundation for the understanding of the role and possible mechanism of CmPht1;2 in the process of phosphorus absorption,and also provides the possibility to breed plant varieties with high phosphorus utilization through transgenic technology.