Functional Analysis Of COST And LSD Genes In Response To Abiotic Stress In Popla

The fragile ecological environment and the increasing demand for wood in China have highlighted the contradiction between supply and demand of forest economic development.In order to improve the ecological environment and alleviate the contradiction between supply and demand of wood,it is urgent to increase plantation cultivation.However,with the increase of global temperature and the instability of rainfall patterns,salt stress and drought stress seriously restrict the survival and yield of trees in saline-alkali land and water-deficient areas during plantation cultivation.It is well known that programmed cell death(PCD)can control the number of cells by eliminating damaged,aged or unnecessary cells to maintain cell homeostasis against stress environments.At the same time,autophagy and Lesion Simulated Disease(LSD)are special PCD in plants,which play an important role in the process of plant resistance to biotic and abiotic stress.Poplar(Populus)is an important economic afforestation tree species widely distributed in China,and plays a vital role in ecosystem stability and wood production.At the same time,poplar has completed genome sequencing with its small genome advantage,and established a mature genetic transformation system,which has become a model species of woody plants to study the cellular and molecular mechanisms of forest unique biology.Therefore,in this study,poplar was used as the main material to reveal the mechanism of poplar under salt or drought stress by excavating the stress resistance genes such as autophagy and lesion mimicry,so as to provide gene resources and theoretical basis for the directional design and breeding of poplar stress resistance molecules.At present,the molecular mechanism of autophagy and cytopathic response involved in response to abiotic stress in woody plants is still unclear.Therefore,in this study,the constitutively stressed 1(COST)and Lesion Simulated Disease(LSD)genes that can regulate the autophagy pathway in poplar were selected as the research objects,and the members PtCOST3 and PtLOL1b that were sensitive to stress response were screened by bioinformatics analysis and abiotic stress response analysis.Subsequently,by creating poplar overexpression lines of PtCOST3 and PtLOL1b,the mechanism of their participation in poplar response to salt stress and drought stress was analyzed.The main conclusions of this paper are as follows:(1)Eleven PtCOST genes were identified in the poplar genome and distributed on eight chromosomes.Phylogenetic analysis showed that they were divided into 4 groups and experienced 2 tandem duplication events and 7 fragment duplication events.(2)The complementation experiment of Arabidopsis cost1 mutant showed that PtCOST3 was a functional homologous gene of Arabidopsis COST1 and played a role as a negative regulator in response to salt stress.(3)Salt stress treatment of PtCOST3 overexpression lines found that the number of autophagosomes in transgenic lines decreased,which was more sensitive to salt stress.This result indicates that PtCOST3 plays a negative regulatory role in poplar resistance to salt stress by regulating autophagy activity.(4)Subcellular localization results showed that PtCOST3 and PtATG8 were localized in the cytoplasm and nucleus.Yeast two-hybrid,BiFC and LUC experiments showed that PtCOST3 interacted with PtATG8 and localized to autophagosomes.(5)Yeast one-hybrid and dual luciferase activity analysis showed that PtERF106 was the upstream gene of PtCOST3 and inhibits the transcriptional activity of PtCOST3(6)Five PtLSD genes were identified in the poplar genome and distributed on four chromosomes.Phylogenetic analysis showed that they were divided into three groups and experienced two fragment replication events.The structure of PtLSD gene is highly conserved,with similar characteristics and three LSD domains.(7)The expression of PtLOL1b gene was induced by drought stress.Overexpression of PtLOL1b in poplar increased tolerance to drought stress.(8)Under drought stress,overexpression of PtLOL1b significantly enhanced ABA sensitivity,reduced stomatal size,improved water use efficiency,and reduced transpiration.(9)Under drought stress,overexpression of PtLOLlb enhanced the activity of antioxidant enzymes and proline content,thereby accelerating the scavenging of reactive oxygen species.In summary,in this study,the functional identification and mechanism of the constitutive salt tolerance gene PtCOST3 and the lesion-one-like gene PtLOL1b in poplar were studied,indicating that PtCOST3 affects poplar biomass accumulation and salt sensitivity by negatively regulating autophagy.On the contrary,the lesionone-like gene PtLOL1b positively regulated the activity of antioxidant enzymes and proline content,accelerated the scavenging of reactive oxygen species,weakened oxidative stress,and enhanced the tolerance of poplar to drought stress.In summary,this study on the function of PtCOST3 and PtLOL1b under abiotic stress will provide gene resources and theoretical basis for the directional design and breeding of poplar resistance molecules.