Physiological And Molecular Responses Of Trollius Chinensis Seedlings To Waterlogging Stress And Subsequent Drainage

Global climate change significantly affects precipitation patterns in many parts of the world.Many areas are often waterlogging due to extreme rainfall events.Waterlogging has become one of the major natural disasters that threaten plant growth and development around the world.Therefore,understanding the response mechanism of plants to waterlogging stress is very important for breeding waterlogging-tolerant varieties and developing waterlogging-tolerant cultivation techniques.Trollius chinensis is one of the important medicinal and ornamental plants in my country,and has high economic value.However,there are no reports on the research on T.-chinensis under waterlogging stress.In this study,the seedlings of T.chinensis were taken as the research object,and the response of physiological and biochemical indicators and gene expression in different stress periods under waterlogging stress and after the stress was relieved was studied,and the mechanism of the response of T.chinensis seedlings to waterlogging stress was preliminarily explored.The main findings are as follows:（1）Under waterlogging stress,the physiological characteristics of root growth of T.chinensis were affected,and the morphological growth parameters as well as root vigor were significantly reduced,while the content of reactive oxygen species（ROS）,proline（Pro）,soluble sugar（SS）,and soluble protein（SP）increased in the root system,and the upward trend of WF-treated roots was more significant than that of WL-treated roots.The activities of glycolysis-related anaerobic respiratory enzymes,such as alcohol dehydrogenase（ADH）and pyruvate decarboxylase（PDC）,increased significantly with increasing waterlogging intensity and time,suggesting that glycolysis plays a key regulatory role under waterlogging stress.After the stress drainage was released,the physiological indexes of the remaining roots of WL and WF treatments did not fully recover to the CK level,except for the root malondialdehyde（MDA）of WL treatment which recovered to the control（CK）level.Photosynthesis of T.chinensis leaves is inhibited,but photosynthetic gas exchange parameters were less affected in WL treatment compared to WF treatment,and chlorophyll（Chl）content of leaves were all decreased,while ROS content and leaf Pro,SS and SP content of T.chinensis leaves were increased.The enzyme activities related to T.chinensis leaves treated with WL and WF showed that the superoxide dismutase（SOD）,peroxidase（POD）and glutathione reductase（GR）enzyme activities in T.chinensis leaves showed an increasing trend,the content of reduced ascorbic acid（As A）and reduced glutathione（GSH）also showed an increasing trend,and the content of abscisic acid（ABA）also increased under waterlogging stress when compared with CK,and the increasing trend of physiological and biochemical indexes was more significant under WF treatment than under WL treatment.After the stress drainage was removed,leaf relative water content（RWC）,intercellular CO₂concentration（C_i）,POD activity,Pro content,SS content,As A content,and Ascorbate peroxidase（APX）activity were restored to CK level under WL treatment,while only leaf Pro content,SS content,As A content,and APX activity were restored to CK level under WF treatment.T.chinensis leaves under WL and WF treatments maintained the balance of redox system among plants by increasing ROS content as well as antioxidant system,which slowed down the inhibition of growth of T.chinensis by waterlogging stress.（2）Transcriptome sequencing yielded 1182 differentially expressed genes（DEGs）,of which307 were up-regulated DEGs and 875 were down-regulated DEGs.GO enrichment analysis of DEGs revealed that,in terms of biological processes,they were mainly annotated to photosynthesis,energy production,photosynthesis and light reactions;in terms of cellular components,they were mainly enriched in pigment bodies,grapheme and chloroplast fractions;and in terms of molecular functions,they were mainly distributed in chlorophyll binding.The KEGG enrichment analysis of DEGs found that it was mainly in photosynthesis,photosynthesis-antenna protein,metabolism and other processes.The results of this experiment were compared by the Plant TFDB database,and a total of 397 transcription factors were screened.Among them,12 transcription factors showed differential changes under waterlogging stress.The most enriched was the FAR1 transcription factor family,followed by the b HLH,C3H,AP2/ERF,NAC,WRKY,and MYB transcription factor families.In this study,we systematically explored the physiological and molecular mechanisms of T.chinensis seedlings in response to waterlogging stress from various perspectives,including root growth physiology,leaf photosynthetic physiology,osmoregulation and oxidative stress.T.chinensis is a waterlogging-tolerant species and waterlogging stress induces changes in its physiology and transcriptome levels such as antioxidant,photosynthesis and osmoregulation.This study provides candidate genes that can be used for breeding T.chinensis for waterlogging resistance.