Mechanisms Of Sasm05 On Enhancement Of Zinc Accumulation In Sedum Alfredii Hance

Sedum alfredii Hance is a zinc(Zn)/cadmium(Cd)hyper-accumulating ecotype in China.It has a good potential for repairing heavy metal contaminated soil,but its biomass is small and the remediation efficiency need to be furtther improved.In recent years,using plant growth-promoting bacteria(PGPB)to improve the efficiency of phytoremediation has become a hot point both at home and abroad.In the study,the specific endophytes Pseudomonas fluorescens Sasm05 isolated from the stem of Sedum alfredii was used as the material.A hydroponic experiment was carried out to study the effects and mechanisms of specific endophytes Sasm05 on Zinc accumulation enhancement in Sedum alfredii Hance,and some technology were used by us,such as,three-parent binding method,laser confocal microscopy,inductively coupled plasma mass spectrometry(ICP)and real-time quantitative PCR(q-RT-PCR)and so on.The main results were as follows:1.Sasm05 was successfully tagged by the green fluorescent protein(GFP)by three-parent binding method,and the phenomenon that Sasm05 entered to the surface of roots,roots and stems of Sedum alfredii Hance was observed by laser confocal microscopy.With the increase of Zn concentration,the biomass and Zn concentration of the shoot and root were increased significantly.After the inoculation of Sasm05,the shoot biomass treated by Zn concentration increased by 37.3%to 59.2%compared to the control while the root biomass increased by 58%to 108%;Zn concentration of shoot increased by 16.7%to 54.7%while Zn concentration of root increased by 37%to 40.6%;Chlorophyll concentration increased by 15.3%to 69.8%.At the same time,Sasm05 significantly affected the transcriptional level of HMA,Nramp and ZIP family genes.2.The time course of Zn uptake and transport as affected by Sasm05 inoculation was studied.The results showed that the biomass increased significantly with the increase of cultivation time.At the time of 30 d,the shoot and root biomass with 200μM Zn treatment was increased by 262%and 421%,respectively.The inoculation of Sasm05 further increased the biomass of the shoot and root by 34.5%and 46.8%.Sasm05 increased the Zn concentration in plant,the chlorophyll concentration by 15.3%to 69.8%and the expression of metal ion transporter,for example,the expression of Nramp1 in root was improved by 2.5 to 34.2 fold compared with the non-inoculated control.3.The effects of enhanced inoculation of Sasm05 and IAA on root development and zinc uptake and transport of Sedum alfredii were compared.The results showed that the effect of IAA on root biomass was promoted by low concentration,inhibited by high concentration,and optimum concentration of IAA concentration was 1μM.Sasm05 significantly increased the shoot biomass,which was more obvious than IAA.Sasm05 also could promote the the concentration of Fe,Mg,Mn,Cu,Ca ions in plant,while the IAA effect was not obvious.The futher studies showed that the effects of Sasm05 and IAA on the expression of Nrampl and IRT1 were not consistent,indicating that Sasm05 not only could promote the plant growth by secreting IAA,but also can influence the heavy metal uptake and transport by effect the related gene expression so that promoting the enhancement of Zinc Accumulation in plant.