| Paenibacillus polymyxa SQR-21(SQR-21)was isolated and indentified from the rhizosphere of healthy watermelons grown in a severely diseased watermelon field.In the previous studies,strain SQR-21 showed a tremendous inhibition of pathogen and significant growth promoting effects in vitro,it was considered as plant growth-promoting rhizobacteria(PGPR).Strain SQR-21 also revealed outstanding biocontrol and growth promotion performance under both greenhouse and field conditions.Application of bio-organic fertilizer made with SQR-21 can significantly lower the disease incidence and reduce the number of Fusarium oxysporum f.sp.niveum(FON)in the pathogenic soil In the previous studies,great achievements were made from a large number of research on the interactions among strain SQR-21,FON and watermelon.But there are still many mechanisms still limited known.It is of great significance to deeply understand the mechanism between SQR-21 and rhizosphere interaction,especially for guiding the rational application of SQR-21.In this study,SQR-21 and FON were used as target strains and we adopted hydroponic experiment method:(1)the differences of watermelon root gene transcriptional expression after colonization by SQR-21 and FON;(2)the changes of root protein expressions after the colonization by SQR-21,FON or both of them;(3)the dynamic changes of root protein expression during the interaction between microorganism(SQR-21 or FON)and watermelon.The main results obtained were summarized as follows:1.In this study,we adopted hydroponic split-root method in the vegetative growth stage of watermelon.In the one side of the split-root box,get the roots inoculated with Paenibacillus polymyxa SQR-21,pathogen FON,or both of them;in the other side,no inoculations on roots.Five following treatments were designed:CK(control):no inoculation in both sides of the system;B-CK:inoculated with FON,the no inoculation side;C-CK:inoculated with SQR-21,the no inoculation side;D-CK:inoculated with SQR-21 and FON in same room,the no inoculation side;E-CK:inoculated with SQR-21 and FON in different room,the no inoculation side.The results showed that,by comparing B-CK(inoculated with FON)with CK,there were 38 genes significantly regulated,among which 2 genes were up-regulated and 36 genes were down-regulated.By comparing C-CK(inoculated with SQR-21)with CK,there were 3068 genes significantly regulated,among which 1817 genes were up-regulated and 1251 genes were down-regulated.By comparing D-CK(inoculated with FON and SQR-21 in the same room)with CK,there were 2118 genes significantly regulated,among which 1296 genes were up-regulated and 822 genes were down-regulated.By comparing E-CK(inoculated with FON and SQR-21 in different rooms)with CK,there were 2511 genes significantly regulated,among which 1380 genes were up-regulated and 1131 genes were down-regulated.Differentially expressed genes mainly include the regulation of basal metabolism(mainly were carbohydrate metabolism and transport,amino acid metabolism and transport,energy generation and transformation),biosynthesis of secondary metabolites,transport,signal transduction and defense mechanisms.The results showed that SQR-21 could promote watermelon growth by inducing the expression of energy metabolism related genes of watermelon,and meanwhile,inducing the expression of signal transduction and disease resistance-related genes,regulated the root resistance protein and enhancing plant disease resistance.2.Hydroponic split-root method was also used to analyze watermelon root proteomics.By comparing the treatments B-CK(inoculated with FON)and the control CK,the result showed that 69 proteins were differentially expressed when compared with control.Among those,37 and 32 proteins were up-regulated and down-regulated respectively.By comparing the treatments C-CK(inoculated with SQR-21)and CK,the result showed that 119 proteins were differentially expressed.Among those,57 and 62 proteins were up-regulated and down-regulated,respectively.By comparing the treatments D-CK(inoculated with both SQR-21 and FON)and CK,the result showed that 130 proteins were differentially expressed.Among those,69 and 61 proteins were up-regulated and down-regulated respectively.GO analysis and KEGG enrichment analysis showed that inoculated with SQR-21,FON and both of them,the molecular functions of differentially expressed proteins were mainly consisted of binding protein and oxidation-reduction related proteins.In the enrichment of pathways,differentially expressed proteins in different treatment all enriched in metabolic pathways,biosynthesis of secondary metabolites,carbon metabolism,glycolysis pathway.The basal metabolism of root cells in the watermelon has a certain effect in different inoculation treatment In C-CK and D-CK treatments,the energy metabolism and photosynthesis-related proteins in the watermelon roots was relatively higher,and the enrichment degree of resistance-related proteins and their participating metabolic pathways was relatively high when compared with the control,indicating that SQR-21 could promote the growth of watermelon plants,induce disease resistance protein,but also can reduce the pathogen FON damage to watermelon plants.3.We assumed that it is various interactions between watermelon and microbes at different time point.At vegetative growth stage of watermelon,inoculated with SQR-21,pathogen FON,or both of them after 10,20,and 30 days,the roots from non-inoculation side were collected for proteomics analysis.The result show that,after FON inoculated,t there were 57 up-regulated and 50 down-regulated proteins in the early stage(10 days);63 up-regulated and 112 down-regulated proteins in the middle stage(20 days);23 up-regulated,30 down-regulated proteins in the later stage(30 days).Also,after SQR-21 inoculated with the watermelon root,there were 61 up-regulated and 32 down-regulated proteins in the early stage(10 days);28 up-regulated and 23 down-regulated proteins in the middle stage(20 days);50 up-regulated and 64 down-regulated proteins in the later stage(30 days).When both SQR-21 and FON inoculated with the watermelon root,there were 95 up-regulated and 68 down-regulated proteins in the early stage(10 days);66 up-regulated and 124 down-regulated proteins in the middle stage(20 days);27 up-regulated and 23 down-regulated proteins in the later stage(30 days).At early stage,basal metabolic-related proteins,regulatory-related proteins,antioxidant stress and tolerant proteins were up-regulated,which could enhance the adaptation of plants to the external environment.In the middle and late stages,signal transduction proteins and disease-resistant proteins expression were more activity.With the watermelon growth process changes,the root system gradually improved,the adversity self-regulation ability is improved,conducive to improving the resistance of watermelon.All the results in this study showed that inoculation with SQR-21 or FON were able to induce the expression of resistance gene and proteins of watermelon root.Besides,strain SQR-21 can also induce the expression of genes related to metabolism,enhance disease resistance in watermelon and promote plant growth.Also,the protein expression was also dynamic changes after colonized by microbes. |
PDF Full Text Request