Physiological And Genetic Functions Of Arabidopsis Thaliana Related Mutants In Response To Low Phosphorus Stress

Phosphorus is an essential nutrient for plant growth and development,it is also a limited and non-renewable resource.The total phosphorus content of the soil is not low in the world,but most of them are in the form of organic phosphorus,or combined with iron,calcium and aluminum,which cannot be directly used by plants.The lack of soil phosphorus nutrition and the poor mobility of plants themselves have become an important factor limiting agricultural reduction.In order to cope with phosphorus deficiency stress,plants have evolved into a variety of adaptation mechanisms.The important changes are plant acidification,root growth inhibition,anthocyanin accumulation,and increase in root hair density.Previous studies have shown that plants secrete protons through the roots under low phosphorus stress,which caused the rhizosphere acidification of soil,activated the insoluble phosphate in the soil.And then the effect of phosphorus utilization increased.However,the molecular mechanism is still unclear by which plants perceive low-phosphorus signals and cause rhizosphere acidification to increase the effective utilization of phosphorus.In order to reveal the molecular mechanism of plants adaptation to low phosphorus stress,our research group screened a strain of Arabidopsis mutant p1-31 that was not sensitive to low phosphorus stress.The results showed that the growth trend of p1-31 grown on MS medium was basically the same as wild type col-0.When cultured in LP medium for 12 d,the color of wild type Col-0 leaves was purple,while p1-31had no significant change in leaf,and the anthocyanin content of leaves was 0.29 times of WT.In addition,the main root growth of WT and p1-31 was inhibited under low phosphorus stress,but the degree of inhibition of p1-31 was significantly lower than that of WT,and the length of p1-31 main roots was about1.69 times that of wild type.The growth of p1-31 was also significantly better than WT,and the biomass of p1-31 leaves was 1.9 times that of WT,its root biomass is also slightly higher than wild type under low phosphorus stress.The phosphorus content in the root of mutant p1-31 was 1.41 times higher than that of the wild type under low phosphorus stress.The results of RT-PCR and qRT-PCR showed that the expression level of PHT1;1 in the mutant p1-31 was significantly higher than that of WT under low phosphorus stress.Genetic analysis showed that p1-31 was a single recessive mutant in Col-0 background.Through map-based cloning technology analysis,the preliminary position p1-31 mutations in II chromosome.The mutant p180 was screened from the Arabidopsis seed bank according to the pH in situ chromogenic method of the medium containing bromocresol purple.The seeds were spotted on normal MS for 8 days and then cultured in MS and LP medium containing bromocresphenol violet for 28 hours.It was found that the color around the root of p180 was significantly yellow,indicating that p180 was a low-phosphate-induced rhizosphere acidification enhanced mutant.Sodium vanadate,an H⁺-ATPase activity inhibitor,can inhibit the rhizosphere acidification enhancement reaction of p180 induced by low phosphorus.Therefore,the enhancement of p180 rhizosphere acidification is related to the activity of H⁺-ATPase.qRT-PCR analysis showed that the expression intensity of AHA1 and AHA6 in p180 plants was significantly higher than that of wild type under low phosphorus stress.It is speculated that P180 may negatively regulate the expression of AHA1 and AHA6.Analysis of the mutation site indicated that the p180 mutation site was located on IV chromosome.After 13 days of treatment under low phosphorus stress,the length of the main root of mutant p180 was significantly shortened,anthocyanin accumulation was increased,and the content of inorganic phosphorus in the root was decreased.The results showed that the deletion of gene P180 affected the mutant response to low phosphorus stress.Through bioinformatics analysis,the gene mainly encodes inositol-5-phosphatase,which belongs to the inositol-5-phosphatase family.The phosphatidylinositol?PI?signaling pathway plays an important role in the growth and development of plants and in the response of cells to changes in the external environment.In Arabidopsis,inositol polyphosphate-5-phosphatase?5PTase?is a key enzyme in the PI pathway which consist mainly of15 members.In mammalian cells,5PTase phosphorylates IP₃ in the PI signaling pathway to inactivate IP₂.Then 5PTase is broken down into free inositol and participates in the next round of signal cycling.In Arabidopsis,5PTase affects the growth and development of plant by affecting the process of plant development and signal response.Studies have shown that the PI pathway is widely involved in physiological responses in plants,such as plant defense and osmotic pressure regulation.The phenotype of p180 suggests that the phosphatidylinositol?PI?signaling pathway may also be involved in the response process of low phosphorus stress in plants.