Study On The Invasion Mechanism Of Wedelia Trilobata Under Simulated Drought Stress

Alien plant invasion is one of the biggest threats to native biodiversity.As global climate change intensifies,droughts occur frequently,increasing or changing the negative impact of invasive plants on natural ecosystems.Studies have shown that future climate change may directly lead to increased competitiveness of invasive plants in invasive sites,which intensifies invasion,but how these invasive plants change their competitiveness,and which metabolic pathways or regulatory mechanisms are unclear.Therefore,our study intends to compare the phenotypic characteristics,physio-ecological response and endogenous hormones of the exotic plants Wedelia trilobata and Wedelia chinensis under the simulated drougt environment and the simulated drought environment with the gibberellin synthesis inhibitor Paclobutrazol(PAC),the regulation law of the W trilobata to the simulateddrought environment was explored,and combined with the comparative transcriptome data to reveal the internal mechanism of the invasion of the exotic plant W trilobata under the simulated drought environment.The main research results of this paper are as follows:(1)The physio-ecological response of the two plants to simulated drought environment shows that: PEG simulated drought and natural drought could inhibit the growth of W.trilobata and W.chinensis while affect their antioxidant systems(POD,CAT,proline,MDA)and endogenous hormone content(ABA,IAA,GA).Compared with natural drought,PEG simulated drought stress has more significant inhibitory effects on the growth of the two plants,such as leaf number,plant height,root development,chlorophyll content,etc.Under the condition of natural drought(D-6),the root length of W.trilobata increased significantly,but the root length of W.chinensis did not change significantly.Whether it is PEG simulated drought or natural drought treatment,compared with the control treatment group,the contents of CAT,proline,and MDA in the leaves of W.trilobata and W.chinensis increased significantly,but the POD content did not change significantly.At the same time,the ABA content of the leaves and roots of W.trilobata increased significantly under drought conditions,while the ABA content of W.chinensis increased,but the roots and leaves responded differently to different drought patterns.Under the two treatment modes,the ratio of ABA / IAA and ABA / GA in the under-ground part of W.trilobata decreased significantly,and the ratio of ABA / IAA in the ground part of W.chinensis decreased significantly,this shows that the regulation pattern of endogenous hormones between W.trilobata and W.chinensis in the drought environment is not the same or similar.(2)By comparing the effect of adding PAC on the growth of two plants under PEG simulated drought treatment,it was found that the addition of PAC would reduce the negative effects of PEG simulated drought treatment on the growth of the two plants,and the effect on W.trilobata was mainly reflected in the number of leaves,Plant height and chlorophyll content,and the effect on native weed W.chinensis is mainly reflected in the plant height,root length,chlorophyll content.At the same time,compared with PEG simulated drought,the addition of PAC significantly increased POD and CAT activity in the leaves of W.trilobata.In addition,the contents of proline and MDA decreased significantly,and the CAT activity,proline and MDA content in the leaves of W.chinensis decreased significantly,indicating that the addition of PAC in drought environment may be more beneficial to alleviate the oxidative damage of W.trilobata.Compared with the PEG simulated drought,the addition of PAC can also significantly increase the ABA content of different tissue parts of W.trilobata and W.chinensis.At this time,the IAA content of the leaf and stem segments of W.trilobata and the GA content of the root also increased significantly,while the W.chinensis only the root The IAA content increases.This shows that although the addition of PAC can alleviate the negative effects of PEG simulated drought on the growth of the two plants,the mechanism of impact on the two plants is different,so the phenotypic responses of the plants are also different.(3)Using RNA-seq sequencing technology,88,071 of W.trilobata and 80,220 Unigenes of W.chinensis were obtained.Annotating the Unigenes of the two plants based on the four databases of Nr,Swiss-Prot,KEGG and KOG/COG showed that 20,616 and 22,478 Unigenes of W.trilobata and W.chinensis were respectively annotated.Among them,there are 6821 differentially expressed genes in WTCK-vs-WT75,8909 differentially expressed genes in WTCK-vs-WT75 P,4134 differentially expressed genes in WCCK-vs-WC75,and 3797 in WCCK-vs-WC75 P.Genes are differentially expressed,and these up-regulated genes are mainly concentrated in genes related to catalytic activity in the molecular function category.The differentially expressed genes of W.trilobata and W.chinensis mainly involved in phenylpropane metabolism,ascorbic acid and aldonic acid metabolism,amino sugar and nucleotide sugar metabolism,folic acid biosynthesis and other metabolic pathways when PEG simulated drought and PAC on W.trilobata.It mainly involves glycine,serine and threonine metabolism,cysteine and methionine metabolism,amino sugar and nucleotide sugar metabolism,carbon source metabolism,ABC transport and other metabolic pathways in W.chinensis.