| Plant root exudates are key factors in shaping the rhizosphere microbial community,thus directly or indirectly influencing plant response to environmental stress and nutrient uptake.Currently,studies on the gene-saline-alkali stress-secretion-rhizosphere microbial relationships are very limited.In this study,we analyzed the effects of salinealkali stress on Arabidopsis thaliana(Arabidopsis)root exudates by high-performance liquid chromatography using the At-cdpk;and the effects of exogenous application of differential root exudates on the diversity and structure of the Arabidopsis soil microbial community,as well as rhizosphere soil physicochemical properties and soil enzyme activities using Illumina Mi Seq high-throughput sequencing technology.The main findings are as follows:1.Analysis of Arabidopsis related phenotypes,and organic acids in root exudates under saline-alkali stressThe phenotype,biomass and chlorophyll of At-cdpk and WT were analyzed.The results showed that under saline-alkali stress,the At-cdpk showed significant yellowing and wilting of leaves and a significant decrease in chlorophyll content compared with WT.Three low molecular organic acids,oxalic acid,citric acid,and succinic acid,were detected in the root exudates of Arabidopsis under saline-alkali stress by highperformance liquid chromatography.The oxalic acid content in the root exudates of Atcdpk with the CDPK gene was significantly lower than that of WT.2.Effects of saline-alkali stress on oxalic acid-related genes in ArabidopsisThe expression of CDPK genes and oxalate transporter-related genes At SULTR2;1,and At SULTR2;2 in Arabidopsis under saline-alkali stress was analyzed by q RT-PCR.The results showed that the results indicated that the At CDPK gene was not expressed in the At-cdpk.At CDPK,At SULTR 2;1 and At SULTR 2;2 genes were significantly upregulated in the WT after saline-alkali stress.The genes were also up-regulated in the Atcdpk.,but to a lesser extent than in WT.3.Effects of exogenous applied oxalic acid on the diversity and structure of soil bacterial communities in the rhizosphere of ArabidopsisAnalysis by 16 S r RNA high-throughput sequencing revealed that compared with wild-type Arabidopsis and mutations in the CDPK gene reduced the diversity of the Arabidopsis soil rhizosphere bacterial community and decreased the abundance of Blastococcus,Microvirga,Gaiella,Rubrobacter,Arthrobacter,Nocardioides,and Solirubrobacter in abundance.Exogenous application of oxalic acid increased the diversity of the soil bacterial community between At-cdpk rhizosphere and increased the abundance of Gaiella,Blastococcus,Acidobacter(RB41),Microvirga,Rubrobacter,Solirubrobacter,and Microlunatus abundance.PCo A analysis revealed that exogenous application of oxalic acid partially restored the rhizosphere soil bacterial community structure of At-cdpk under saline-alkali stress,bringing it closer to WT,and significantly enriching key groups of bacteria associated with plant growth promotion,environmental remediation,and phytopathogenic control,such as Acidobacteriota,Planctomycetota,Nitrospirota,Methylomirabilota.The functional prediction results showed that the relative abundance of functional genes differed significantly between At-cdpk and WT,but the results were similar between exogenous application of oxalic acid and WT.It indicates that exogenous application of oxalic acid can improve information storage and processing,cellular processes and signaling and transformation in soil bacterial communities,and restore the abundance of functional genes with synthetic and metabolic functions in a part of soil bacterial communities.4.Effects of exogenous applied oxalic acid on the diversity and structure of rhizosphere soil fungi communities of ArabidopsisITS high-throughput sequencing analysis revealed that the rhizosphere soil fungal community diversity of At-cdpk was reduced and the relative abundance of beneficial fungi such as Acremonium,Mortierella,and Schizothecium was reduced compared with that of WT.Exogenous application of oxalic acid increased the fungal community diversity in the rhizosphere soil of At-cdpk and increased the relative abundance of beneficial fungi such as Mortierella,Leucoagaricus,and Arthrobotrys in the rhizosphere soil of Arabidopsis.Meanwhile,the relative abundance of some pathogenic fungi or potential pathogenic fungi,such as Acrophialophora and Tausonia,was reduced.By PCo A analysis,exogenous application of oxalic acid partially restored the rhizosphere soil fungal community structure of At-cdpk Arabidopsis under saline-alkali stress,making it more similar to that of WT.Exogenous application of oxalic acid also increased the abundance of nutrient-type functional fungi with beneficial effects on plant growth and decreased the abundance of pathogen-type functional fungi causing the disease to plants in the rhizosphere soil.5.Effect of exogenous application of oxalic acid on rhizosphere soil physicochemical properties and soil enzyme activities in ArabidopsisThe results of physicochemical properties and soil enzyme activity measurements of the rhizosphere soil of Arabidopsis showed that the organic matter,alkaline nitrogen,and available potassium contents,the enzyme activities of soil urease,catalase,sucrase,and alkaline phosphatase were significantly lower,and the soil p H value and conductivity were significantly higher in the rhizosphere soil of At-cdpk compared with WT.Exogenous application of oxalic acid increased the organic matter,alkaline nitrogen,and available potassium content increased the enzymatic activities of soil urease,catalase,sucrase,and alkaline phosphatase,and decreased soil p H value and conductivity in the rhizosphere soil of the At-cdpk. |
