Mechanism Studies On The Utilization Of Phosphorus Resources In Invasive Plant Wedelia Trilobata

The invasion of alien plants is a serious threat to global ecological health and environmental security.The prevention and control of invasive plants depends on the study of their invasion mechanisms.At present,although many hypotheses have been proposed to explain the mechanism of invasive plants' successful invasion,the underlying reasons for the rapid colonization and spread of invasive plants in nutrientpoor areas are still unclear.In this study,Wedelia trilobata,a malignant weed that invaded South China,was used to study the utilization of phosphorus in different forms;W.trilobata was screened from an endophytic strain to verify its important role in the utilization of refractory phosphorus;W.trilobata was compared with Alternanthera philoxeroides,Solidago canadensis,and Wedelia chinensis for phosphorus utilization;The internal molecular mechanisms and metabolic pathways of W.trilobata's efficient utilization of insoluble and low phosphorus forms were further analyzed from the aspects of transcriptome and metabolome.The main results of this study are as follows:1.The growth response of W.trilobata and W.chinensis in different culture periods under insoluble and low phosphorus conditions were different.During the short-term cultivation,the growth of W.trilobata under various phosphorus treatments had no significant difference.During the middle and long-term cultivation,only the growth of low phosphorus treatment was inhibited,and the growth of insoluble phosphorus treatment had no significant effect.The growth of the W.chinensis in each period under the conditions of insoluble and low phosphorus was significantly inhibited.In the experiment of different phosphorus forms,W.trilobata could make better use of insoluble phosphorus forms such as hydroxyapatite and aluminum phosphate,and could also efficiently use low phosphorus forms.However,the W.chinensis cannot effectively use all other different forms of phosphorus.2.In this part of the study,a high-efficiency phosphate-solubilizing bacteria WTB-JS006 was selected from 45 endophytes of W.trilobata isolated from our laboratory.According to SEM observation and analysis,the strain was rod-shaped with a single bacteria diameter of about 2.1-2.5 ?m.After 16 S r RNA sequencing and comparison,it was found that the similarity between this strain and Pseudomonas rhodesiae reached 98%,and its phosphorus solubilization coefficient was 2.68,and the phosphorus solubilization amount could reach 604 ?g/m L.The endogenous phosphorus solubilizing bacteria WTB-JS006 of W.trilobata was tested against inoculation.The results showed that the biomass and phosphorus content of W.trilobata after inoculation with phosphorus solubilizing bacteria significantly increased under the conditions of insoluble phosphorus.But it had no significant effect on the growth and phosphorus content of W.chinensis.3.In order to eliminate the dissolution of phosphate by plant endophytes or soil microorganisms,this part of the study used an aseptic culture system to compare the differences in the utilization of insoluble and low phosphorus resources between W.trilobata and other two invasive plants and native plant.The results showed that there was no significant difference in the growth of W.trilobata under different phosphorus treatments,while the growth of the other two invasive plants and native plant under insoluble and low phosphorus treatments was significantly inhibited.4.The transcriptome and metabonomic analysis of W.trilobata and W.chinensis that grow under insoluble and low phosphorus stress further reveal their intrinsic molecular mechanisms for responding to phosphorus deficiency stress.Compared with normal phosphorus(Wt-KP),W.trilobata insoluble phosphorus(Wt-Ca P)had 4,428 differential expression genes(DEGs),which involved the interaction between plants and pathogens and pathways such as phenylpropane biosynthesis;There were 51 different metabolites involved in 39 metabolic pathways,mainly glutathione metabolism and phenylpropane biosynthesis.Compared with the normal phosphorus(Wt-KP),the W.trilobata low phosphorus(Wt-LP)had 4 DEGs,42 different metabolites were involved in 39 metabolic pathways,mainly lysine degradation and ?-alanine Metabolism.W.chinensis normal phosphorus(Wc-KP)had 49471 DEGs compared with W.trilobata normal phosphorus(Wt-KP),which were involved in planty-pathogen interaction and photosynthesis pathways.There were 256 different metabolites involved in 82 metabolic pathways,mainly arachidonic acid metabolism and citrate cycle(TCA cycle).W.chinensis insoluble phosphorus(Wc-Ca P)had 50532 DEGs compared with W.trilobata insoluble phosphorus(Wt-Ca P),which were involved in homologous recombination and glycerol metabolism.There were 241 differential metabolites involved in 81 metabolic pathways,mainly valine,leucine and isoleucine biosynthesis and arachidonic acid metabolism.W.chinensis low phosphorus(Wc-LP)had 58,832 DEGs compared with W.trilobata low phosphorus(Wt-LP),which were involved in photosynthesis and plantation-pathogen interactions.There were 207 differential metabolites involved in 76 metabolic pathways,mainly ?-linolenic acid metabolism and the biosynthesis of keratin,amber and wax.In summary,the invasive plant W.trilobata can use its own developed root structure,high-efficiency endogenous phosphorus solubilizing bacteria,and gene expressions,metabolites and metabolic pathways under the stress of insoluble and low phosphorus.It has the advantage of effective phosphorus resource absorption and utilization.These properties contribute to the rapid spread and widespread distribution of the invasive plant W.trilobata.This research clarifies the internal mechanism of the efficient use of resources of W.trilobata,and to a certain extent provides an important theoretical basis for actively promoting scientific prevention and effective control of invasive plants.