Phosphorus Deficiency Regulates Root Growth And Transcripts Of Genes Involved In Stem Cell Formation In Soybean Root Tips

Phosphorus(P)is one of essential nutrients,which are necessary for plant growth and development,and thus play an important role in plant life cycle.Phosphate(Pi)fertilizers are easily fixed on the soils,and thus result low Pi availability on soils.During the long-term evolution process,plants develop a set of adaptive strategies to P deficiency.Among them,it is well known that changes of root morphology and architecture are common responses of plants to P deficiency.However,few studies were conducted to investigate the roles of the stem cell related genes in the adaptive strategies in plants.In the present study,using a soybean cultivar,YC03-3,and one transgenic line with GmPP2 suppression as materials,dynamic changes of root morphology and architecture in soybean seedlings were investigated during shot-term P deficiency using the optimized two-dimensional paper culture system in situ.Subsequently,effects of long-term P deficiency on root morphology and Pi accumulation were assayed using nutrient solution culture.Furthermore,transcripts of stem cell related genes were analyzed in both soybean tap root tips and lateral root tips at two P levels.The results provide a basis for further understandings about involvement of stem cells related genes in plant adaptive strategies to P deficiency,the main results are as follows:1.The two-dimensional paper culture system was optimized for dynamic analysis of soybean root growth mainly through shading the paper pouch and pre-soaking it in nutrient solution.The results showed that P deficiency did not influence tap/lateral root growth,base root growth,root surface area and lateral root number between 1 to 7 d of plant growth.However,root biomass,total root length and root surface area in seedlings with GmPP2 suppression were lower than those in wild type(WT).Furthermore,base root length in WT was significantly higher than that in seedlings with GmPP2 suppression at low P level.2.Long-term P deficiency on soybean root growth and P accumulations were investigated through nutrient solution culture.The results showed that P deficiency significantly inhibited shoot fresh weight and P content at 14 d.For roots,significant increases of fresh weight,total root length,and root surface areas were observed in WT by P deficiency,but not in transgenic plants with GmPP2 suppression.Moreover,at the same P treatment,root biomass,total root length,and root surface areas in WT were significantly higher than those in transgenic plants.3.Expression pattern of stem cell related genes in soybean tap and lateral root tips were investigated through quantitative RT-PCR.The results showed that their expression patterns were significantly affected by P deficiency.For the tap root tips in both WT and transgenic plants,expression levels of 7 genes were significantly up-regulated by P deficiency,including SHR1,WOX5,ARF10,PIN4,CDF4,ACR4,and CYCD3;3.However,increased transcripts of SCR1,PLT1 and ROW1 were only observed in the tap root of the transgenic plants.For lateral root tips,increased transcripts of 7 genes were observed in both WT and transgenic plants by P deficiency,including SHR1,SCR1,WOX5,ARF10,ROW1,CDF4 and CYCB3;3.Furthermore,at the same P level,transcripts of WOX5,PIN4,ROW1 and ACR4 in the transgenic plants were significantly higher those in WT.These results indicated that GmPP2 might regulate expression patterns of the stem cell related genes in lateral root tips,and thus mediate responses of lateral roots to P deficiency in soybean seedling.