OsSIZ2 Mediated Growth Development And Phosphate Acquisition And Mobilization In Rice

Phosphate plays an important role in plant growth,development and metabolism as one of the fundamental macronutrient.Although abundant in soil,available orthophosphate in soil for acquisition easily be fixed,so that phosphate becomes one of the important factors that limit crop growth and production.SUMO(small ubiquitin-related modifier)has increasingly become the focus in phosphate signaling pathway study,and it is a kind of the post-translational modification form.SIZ(SAP and Miz finger domain)is the SUMO E3 ligase and determines the specific targets.AtSIZ1 can participate in the response to phosphate deficiency by modifying of the transcription factor AtPHR1.In rice,OsSIZ1 is involved in regulation of the responses to phosphate.In addition,OsSIZl regulates root growth and root architecture in deficiency conditions.This paper analyzed the function of another rice SUMO E3 ligase gene OsSIZ2.we analyzed the functions of OsSIZ2 in growth and development,and its involvement in phosphate absorption and translocation by using mutants of OsSIZ2,transgenic rice plants OsSIZ2-Ri and OsSIZ2-Ox.In addition,the study also analyze the different impact of the absence of the two genes in rice by using mutant ossizl as control.The main results are as follows:1.OsSIZ2 expresses in different tissues at different developmental stages in rice and this expressing trends in various parts throughout the growing period are basically consistent by qRT-PCR.These results illustrate that OsSIZ2 is involved in rice vegetative growth and reproductive process.Through the lacking of phosphate deficiency treatment experiment,we found that OsSIZ2 is not very responsible to low phosphate at the transcriptional level.2.Lacking of OsSIZ2 caused a serious impact on rice growth and development.Compared with wild type,ossizl,ossiz2 and OsSIZ2-Ri grew slower with lower germination rate.Compared with OsSIZ2,the influence on seed germination of missing OsSIZ1 more apparent.In the seedling stage,hydroponic experiments found plant height of ossiz2 and OsSIZ2-Ri was significantly shorter,biomass and root length also significantly reduced.In flowering stage,OsSIZ2 affect the anther dehiscence and activity of pollen of rice.The proportion of dehiscent anther every spike and activity of pollen are serious decline in ossiz2,and these cause lower seed setting rate.There is a different effect on seed shape in ossizl and ossiz2.We detected the expression of genes which are related with seed shape,and found OsGS3 may play a major role in influencing the shape of ossizl and ossiz2 in the current study.Those cause lower 1000-grain weight.In addition,changing the expression of OsSIZ2 also have an impact on plant height,tiller number,length of panicle and number of primary branches.These results indicated that OsSIZ2 play an important roles in growth and development.3.Phosphate concentration in rice is significantly increased after knockdown/knockout OsSIZ2.After knockdown OsSIZ2,phosphate concentration in shoot and root in rice is increased in seedling rice,and OsSIZ2 function in Pi-uptake and Pi-mobilization in rice by 32P isotope experiment.Although the different effects of ossiz2 and OsSIZ2-Ri in increasing phosphate concentration,after knockdown/knockout OsSIZ2 of rice caused phosphate concentration in rice is significantly increased at mature stage,The experiment of Pi concentration in the xylem sap at filling stage also indicated that OsSIZ2 function in Pi-uptake in rice.4.Knockdown/knockout OsSIZ2 causes genes which positively regulated by OsPHR2 are repressed.These results suggested that OsSIZ2 may regulate downstream genes by positively regulate OsPHR2.Knockdown/knockout OsSIZ2 causes the expression level of OsPT1 significantly up-regulated but the other Phtl family genes are not.These indicate that phosphate concentration increasing in rice of knockdown/knockout OsSIZ2 may cause by up-regulated expression of OsPT1.The expression of OsSIZl and OsSIZ2 in ossizl and ossiz2 is not up-regulated compared with the wild type.So OsSIZ1 and OsSIZ2 is not functionally redundant in rice.