Identification Of Phosphate Starvation Regulated Cell Wall Proteins In Soybean Roots And Functional Characterization Of GmPAP1-Like

Phosphorus(P)is one of the most essential macronutrient elements for plant growth and development.However,phosphorus could be easily fixed by organic matters or other cations,which results in low P availability in many soils.Therefore,low P stress becomes one of the main constrains for agricultural production.In plant roots,cell walls are directly connected to rhizosphere environments,and are thus the first compartment to perceive and transmit extra-and intercellular signals in many pathways by relying on the enzymatic activities of cell wall proteins(CWPs).In this research,an iTRAQ proteomics assay was conducted with soybean roots to identify water soluble and weakly bound CWPs that are responsive to Pi starvation.In addition,soybeans acid phosphatase(APase)GmPAP1-like gene were identified and isolated from soybean cultivar YC03-3.The subcellular localization and expression pattern of GmPAP1-like were further analyzed.Overexpression of GmPAP1-like resulted in significant increases of root extracellular APase activity in transgenic soybean hairy roots.The main results were shown as follows:1.Hydroponic culture results showed that P influenced the soybean growth and development.Low P stress significantly reduced the shoot biomass,P content in both shoots and roots of soybean.However,no significant differences on root biomasses were observed between the two P treatments.The root traits were also affected by low P stress.Under the condition of low P,the total root surface area,total root length,lateral root surface area,lateral root length and the root APase activity were increased significantly compared with that under P efficient condition.2.Total 60 cell wall proteins(CWP)were found to be significantly regulated by Pi starvation.Among them,31 CWPs were increased under low phosphate deficiency,while 29 CWPs were decreased.These CWPs are mainly involved in the carbon metabolism,REDOX,signal transduction and so on.Subsequent qRT-PCR analysis correlated the accumulation of 70% up-regulated proteins,and 30% down-regulated proteins with their corresponding gene expression patterns in response to P deficiency.3.One up-regulated CWP,the purple acid phosphatase 1-like(GmPAP1-like),was functionally characterized.The expression level of GmPAP1-like was significantly up-regulated under low P stress condition.Moreover,no significant differences were observed on expression of GmPAP1-like among different soybean varieties.The further investigation shows that the GmPAP1-like localized on cell walls;In addition,overexpression of GmPAP1-like resulted in significant increases of root extracellular APase activity in transgenic soybean hairy roots.In conclusion,a total of 60 CWPs with differential accumulation in response to P deficiency were identified by iTRAQ proteomics analysis.Further investigations were conducted to elucidate the properties of one of the CWPs,GmPAP1-like,which might provide important theoretical foundation for soybean breeding.