| In recent years,the global climate change results in extreme weather,such as drought,land salinization and flooding,which are the abiotic stresses that severely limiting plant growth and crop yield.Therefore,the study of plant response to drought stress,salinity stress and waterlogging stress are beneficial for us to understand the molecular tolerance mechanism of plant in the adaption to abiotic stresses.Sesuvium portulacastrum(L.)L.is a worthy of study plant because it adapte to various ecological habitat,which shows drought,salinity and waterlogging stresses tolerance.So far,the researches about S.portulacastrum mainly focused on its physiology and proteomics under salinity stress,fewer researches about its drought stress tolerance and most of them focused on the physiological level,especially studies that looked into its waterlogging tolerance.In order to explore how the S.portulacastrum adapts to drought stress,salinity stress and waterlogging stress in the temporal,and how it common regulates the molecular mechanisms under these three abiotic stresses as well,we performed comparative transcriptome analysis of S.portulacastrum under different abiotic stresses based on Illumina sequencing.The results show that:(1)188.15 GB high quality data contains 723,042,468 clean reads were produced from 33 samples after filtered the raw data,all these sequences were De novo assembled into 104,402 Unigenes,termed it S.portulacastrum's reference transcriptome.Through GO and KEGG annotation,we obtained a comprehensive review of S.portulacastrum's reference transcriptome.(2)A model of S.portulacastrum responses to drought stress in different treating time dimension was build,which shows that,in the first 3 hours under drought stress,ion transmembrane transport,voltage-gated ion channel activity and glutathione peroxidase(GPX)activity related genes were up regulated.While the proline catabolic process and proline dehydrogenase activity related genes were down regulated.During the period of 3 to 6 hours drought stress,starch biosynthetic process,glycogen(starch)synthase activity and amyloplast related genes were down regulated,which promote the accumulation of monosaccharide(such as glucose)in cells,it is beneficial to balance the osmotic stress under drought condition.While under 6 to 12 hours drought stress,genes related to phenylpropanoid and flavonoid metabolic process were up regulated to increase the stress resistance,and genes related to positive regulation of seed germination were down regulated at the same time to reduce the energy consumption and the water demand.(3)A model of S.portulacastrum responding to salinity stress in different treating time dimension was build,which shows that,in the first 3 hours under salinity stress,S.portulacastrum mainly raised a large number of biological events associated with ion transport to inflow of other ions(mainly imported K+ in this stage).At the same time,electron transport chain related genes were down regulated with glutathione peroxidase activity related genes were up regulated,these biological events help alleviate permeability imbalances,ion poisoning and oxidative damage.During the period of 3 to 6 hours under salinity stress,S.portulacastrum mainly dependent on hydrogen ion transmembrane transporter activity to regulate ions balance insteads of other ion transmembrane transport or ATPase activity.Also,it started to up regulated the genes related to energy reserve metabolic process,such as glycogen biosynthetic process and starch biosynthetic process,and the genes related to structural constituent of cytoskeleton were up regulated to reinforce its morphology construction to prepare for the long time salt stress environment.While under 6 to 12 hours salinity stress,S.portulacastrum mainly up regulated the genes related to phenylpropanoid and flavonoid metabolic process to increase the stress resistance.Cell wall and apoplast related genes up regulated in this stage,too,which helped to maintain the cell's basic morphology and to protect the cell's internal structure.(4)A model of S.portulacastrum responding to waterlogging stress in different treating time dimension was build,which shows that,in the first 3 hours under waterlogging stress,S.portulacastrum mainly up regulated the genes related to energy reserve such as cellular respiration and alcohol catabolic process.In this stage,it also built up the protective structure such as cell wall and cytoskeleton to maintain the cell structure.The antioxidant and peroxidase related genes also up regulated to scavenging ROS.During the period of 3 to 6 hours under waterlogging stress,starch biosynthetic process related genes up regulated to provide the source of energy.Until waterlogging after 12 hours,S.portulacastrum start to detect and response to hypoxia,strengthening anaerobic respiration is one of the most important strategies in response to long time waterlogging stress.At this time,phenylpropanoid biosynthetic process and flavonoid metabolic process were up regulated to scavenging ROS and reducing the damage on oxidative stress under waterlogging condition.(5)Compared the number of different expressed genes in S.portulacastrum under drought stress,salinity stress and waterlogging stress,which indicated that S.portulacastrum shows the ability of drought stress tolerance more than salinity stress tolerance,while the least ability of waterlogging stress tolerance.Furthermore,the common regulated genes under drought and salinity stresses are more than which under drought and waterlogging stresses or salinity and waterlogging stresses,which indicated that there were more common regulation mechanisms in response to drought stress and salinity stress,while the mechanism in response to waterlogging stress was quite different from that in response to the others.(6)The common regulated genes that responded to drought and salinity stresses selected and discussed,they been annotated as PYR/PYL,ETR,V-type H+-ATPase,AUX/IAA and PRODH.The common regulated genes helped to explore the common regulation mechanisms in response to drought stress and salinity stress,which shows:(?)When under drought and salinity stresses,it was up regulated abscisic acid receptor PYR/PYL family to promote the transduction of ABA,which adjusted the stomatal aperture to reduce the water loss from it.(?)5.portulacastrum up regulated ethylene receptor ETR to limit the transduction of ethylene signal,finally resulted in increase the leaves growth to maintain photosynthesis,and keep growth while delay the maturation and aging of S.portulacastrum,so that to resist the adverse environmental.(?)Increasing the activity of V-ATPase on the vacuolar membrane,which helped to cause the H+ potential difference beside the vacuolar membrane,which drived the secondary active transport system and reverse transporter to relieve the cell osmotic imbalance and the toxic effect of Na+.(?)The down regulation of proline dehydrogenase promoted the accumulation of proline,which relieved the osmotic imbalance and oxidative stresses under drought and salinity stresses.(7)The relationship between plant hormone signal transduction and the multiple stress adaptability of S.portulacastrum has been investigated,and the results showed that the changes of the plant hormone signal transduction were different under different stresses.Under drought stress,the signal transduction of auxin and abscisic acid were up regulated,while the signal transduction of brassinosteroids,cytokinin and ethylene were down regulated.Under salinity stress,the signal transduction of auxin,brassinosteroids and ethylene were down regulated.Under waterlogging stress,the signal transduction of brassinosteroids,gibberellin and abscisic acid were up regulated,while the signal transduction of ethylene were down regulated.All these signal transduction pathways constitute the mechanisms and strategies of the S.portulacastrum responsed to drought stress,salinity stress and waterlogging stress.In summary,in our research,we have a preliminary understanding of the S.portulacastrum's mechanism responding to drought stress,salinity stress and waterlogging stress in different treating time dimension.If the results of this study are applied to the actual production of the crop cultivation,it will help to improve the utilization of the edge land,such as desert wasteland,salt marshes and coastal wetland,et al.Besides,it also helps to solve the increasing demand for crops because of the growing population. |
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