Nitric Oxide Enhances Phosphate Nutrition In Rice Seedlings By Regulating Phosphate Uptake And Translocation

As one of the most important macro nutrient for biology,phosphorus composes many materials showed a widely biological function in metabolism.In the soil,only phosphate can be used by plants directly and exists in a shortage,leaving phosphate one of the limits for plant growth and yield.Therefore,it is very important to study the molecular mechanism of phosphate uptake and having scientific significance to find a measure to promote the uptake and translocation.Nitric oxide(NO)is a gaseous signal molecule and involves many cellular processes.Although its functions in abiotic stress have been proved,it is still unclear when it comes to mineral nutrients.In this study,NO donor(sodium nitroprusside,SNP),nitric oxide synthetase inhibitor(Nw-nitro-L-arginine,L-NNA),nitrate reductase inhibitor(Tungstate)and nitric oxide scavenger(2-(4-carboxy-phenyl)-4,4,5,5-tetra methylimidazadine-l-oxyl-3-oxide,cPTIO)are used.Depending on laser scanning confocal microscope and quantitative real-time PCR(qRT-PCR),the promotion of NO on phosphate uptake and translocation has been proved.The results are as follows:1.SNP has a concentration dependent promotion on phosphate accumulation in rice seedlings.Phosphate content both in the root and shoot showed a significant increasing when treated by SNP under the concentration less than 30 μm.When treated by 30μm,the promotion stayed at same level in the root while dropped in the shoot compared with 10μm treatment.Increasing the SNP concentration to 50μm,promotion declined in the root while gone in the shoot.2,Nitric oxide enhances phosphate uptake and translocation by phosphate transporters,which showed a various responses.As SNP concentration increased,relative expression level of OsPTIO,OsPT6 and OsPT8 reached the highest at the concentration of 5,10 and 30μm respectively.The expression level of OsPT4 was down-regulated before 10 μm treatment and up-regulated after that.OsPT2,a phosphate transporter gene related to translocation,was up-regulated by SNP at all treatments.3.Nitric oxide plays a role in the phosphate uptake and translocation mechanism.Nitric oxide up regulated the expression of OsMYB2P-1 and OsPHR2,then activated the expression of phosphorus starvation induced genes,finally up regulated the expression of several phosphate transporters as well as an acid phosphatase gene(OsPAP10),enhanced the uptake and translocation.SNP repressed the expression of OsPHO2 and OsPHR1.A negative correlation showed between SNP concentration and OsPHR1.SNP also up-regulated the expression level of OsmiR399k,while repressed the rest of mature OsmiR399.All above,nitric oxide can activate phosphate uptake and translocation in rice seedlings,and promote the accumulation of phosphate by up-regulating phosphate transporters.This result can provide a theoretical support for research on mechanism of phosphate utilize efficiency.