Involvement Of OsPHO2 In Inhibition And Control Of Phenanthrene By Modulating Phosphorus In Rice

Phosphorus(P)is one of the macronutrient elements necessary for plants.It is not only a component of many important compounds in plants,but also plays an important role in a large number of metabolic activities in plants,and can improve plants ability to adapt to the environment.OsPHO2 is the main negative regulator of the inorganic phosphate(Pi)starvation response signaling pathway,and plays an important role in maintaining phosphorus homeostasis in plants.Polycyclic aromatic hydrocarbons(PAHs)is a ubiquitous environmental pollutant.Phenanthrene(Phe),as one of the representatives of polycyclic aromatic hydrocarbons,is highly toxic because it can be absorbed by plants into the food chain,threatening food security and human health has attracted widespread attention.Rice is one of the three main staple foods in China,and the amount of polycyclic aromatic hydrocarbons absorbed by the Chinese population from its grains is significantly higher than that of other countries.Nowadays,the research on PAHs entering and transporting plants has a certain foundation,but it is unclear whether phosphorus will participate in the process of rice inhibiting PAHs and its possible mechanism.In this research,Nipponbare(NP)and ospho2 mutants were used as experimental materials,and hydroponic and pot experiments were conducted to clarify the effect of phosphorus on rice inhibition and control of phenanthrene.The main results are as follows:1.Phenanthrene is absorbed and transported by rice plants and thus affects their growth.Results from hydroponic culture showed that,compared with control treatment,phenanthrene increases root biomass.Rice absorbed and transported phenanthrene,and the transport of phenanthrene from rice roots to the shoots increased significantly with phenanthrene supplies increasing.However,most of the phenanthrene absorbed by rice accumulated in rice roots,and the concentration of phenanthrene in rice roots was 12 times higher than that in the shoots.These suggest that is of practical significance to study the resistance and control mechanism of rice to phenanthrene.2.Phosphorus involves in the absorption process of phenanthrene in rice.Results from hydroponic culture showed that,some genes related to phosphorus absorption would respond to phenanthrene.Under phenanthrene treatment,the expression level of OsPHO2 in the shoot was significantly reduced;the expression levels of Os PT4 and Os PT8 in the control treatment were only 5% and 13% of the expression levels of the phenanthrene treatment treatment in the root.The low phosphate(10 μM)environment promoted the absorption and accumulation of phenanthrene by rice roots,and the sufficient phosphate inhibited it,which indicates that phosphorus plays a role in the process of rice control of phenanthrene.3.OsPHO2 affects the absorption and transportation of phenanthrene by rice.Results from hydroponic culture showed that,compared with the wild type,the OsPHO2 mutants had accumulated phosphorus and phenanthrene in the shoot;compared with the sufficient phosphate supply,the translocation factor of phenanthrene in rice was significant reduced by 87% in the low phosphate treatment;compared with the wild type,the phenanthrene translocation factor of OsPHO2 mutant increased about 4 times.In addition,the collected xylem sap was tested and found that the concentration of phenanthrene in OsPHO2 xylem sap was 2.6 times higher than that of the wild type.These results indicate that the mutation of OsPHO2 can promote the transportation of phenanthrene.4.OsPHO2 affects the distribution of phenanthrene in various parts of the rice mature period.Results from pot experiment showed that,compared with control treatment,phenanthrene increased the tiller number by about 40%,but didn’t affect the yield per plant.The OsPHO2 mutant rice culm phenanthrene concentration was 7-9 times higher than that of the wild type.This indicates that the mutation of OsPHO2 at the mature stage will also promote the transportation of phenanthrene.In summary,through hydroponic and pot experiments,OsPHO2 involves in inhibition and control of phenanthrene by modulating the absorption and transport of phosphorus in rice.