Preliminary Study On The Role Of OsSCL57 In Phosphorus Homeostasis Of Rice

Phosphorus(P)is one of the essential mineral elements for plant growth and development,and it is essential for the metabolism of normal life activities of plants.Phosphorus deficiency and excessive phosphorus can affect the normal growth of plants,so plants will maintain phosphorus homeostasis through a series of regulation.Serine/arginine-rich(SR)protein is an important splicing factors that regulate plant development through alternative splicing and play an important role in plant response to abiotic stresses.To date,little is known about the relationship between SR protein and plant phosphorus homeostasis.OsSCL57 is a member of the SCL subfamily of alternative splicing factors.Now we have found two its transcripts.The results of tissue expression level analysis indicated that OsSCL57 was expressed in different tissues of rice at different stages.Among them,the expression level of shoot was higher than that of root,and the expression level was the highest in leaves.Element-specific induction analysis indicated that OsSCL57 was not induced by phosphorus deficiency in roots and shoots.In order to study the localization of this gene,we transfected the 35S-sGFP-OsSCL57 vector with green fluorescent label into rice protoplasts.The localization results indicated that OsSCL57 was localized in the nucleus.In order to investigate the function of OsSCL57,we constructed three mutant lines:osscl57,osscl57-1,osscl57-2,and 10 overexpressing lines.These transgenic materials were treated with low phosphorus(0.01 mM),normal Kimura(0.091 mM),and high phosphorus(0.45 mM)for 14 days.It was found that the mutants of the gene were all sensitive to high phosphorus,that is,the plants showed short stature and the leaves showed symptoms of necrotic spots,while under normal culture conditions,only the leaves of osscl57 showed necrotic spots.The results of available phosphorus content analysis showed that the content of available phosphorus and phosphorus in the shoots of the mutants under the three phosphorus concentrations was higher than that of the wild type,and more inorganic phosphorus accumulated in the old leaves.The overexpressing material was similar to the mutant,and both showed high phosphorus sensitivity and the available phosphorus content was higher than that of the wild type.Subsequently,we measured the total phosphorus in the mutants and wild type treated with three phosphorus concentrations.The results showed that the total phosphorus content in the shoots was higher than that in the wild type,and there was no difference in the roots.We believe that the roots of the mutant transport more phosphorus to the shoots.Therefore,the phosphorus content in the xylem sap was detected.It was found that the mutant xylem sap had higher phosphorus content than the wild type,which was in line with our expected results.In addition,phosphorus stress changed the angle of the leaves,so we observed the angle of the leaves under the three phosphorus concentrations.It was found that the angle of the mutant leaves was higher than that of the wild type at the three phosphorus concentrations.In summary,we believe that OsSCL57 is involved in the regulation of phosphorus homeostasis rice,and the change of phosphorus content is related to the translocation of phosphorus from the roots to the shoots of rice.In order to elucidate the role of OsSCL57 in the regulation of phosphorus homeostasis in rice,we constructed the OsSCL57-ADARcd overexpression material by TRIBE technology and searched for downstream target genes of OsSCL57 by RNA-seq.We screened thousands of candidate target genes,including some phosphorus-related genes,such as phosphatases,transporters,transcription factors,and splicing factors,all of which may be directly or indirectly involved in phosphorus homeostasis.Among these genes,we selected genes with a percentage of editing close to 0 and a percentage of 100%,and verified the editing efficiency by whole genome sequencing.The results showed that the 100%of the edited genes did undergo base changes,which proved the feasibility of TRIBE in rice.In summary,OsSCL57 is involved in regulating rice phosphorus homeostasis,its mechanism of action is likely to be a downstream gene regulated by OsSCL57,which is achieved by changing the transport of phosphorus from the roots to the shoots.