Correlation Between Salt/alkali Stress Response And Developmental Regulation In Wheat Introgression Lines

Two major topics in plant research field are growing development and stress response.The former focuses on the self-regulation of plants while the latter does on the interaction between plants and environment.In recent years,although many related genes and regulatory pathways have been identified in both topics,their relevance with rather complex still remains unclear.On the one hand,stress can affect cell division&differentiation via affecting accumulation of nutrients,thus repress development of plant.On the other hand,plant can also increase their tolerance to stress by slowing the growth and development.Besides,the mechanism of regulating both development and stress response are closely related,because many stress response-related genes or pathways can also crosstalk with growing development.In breeding,this relationship leads to a conflict between enhancing resistance and ensuring yield.Therefore,it is significance to study the similarities and differences in regulatory mechanisms of growing development and stress response,so as to deepen the understanding of the relationship of plants with the environment.Moreover,finding the common regulatory node between stress resistance and development,and screening the functional genes that promote stress tolerance but do not inhibit development would be a valuable work for breeding application.In the previous research,we constructed introgression lines with different mutant phenotypes via asymmetric somatic hybridization between common wheat cultivar JN177 and Agropyron elongatum.Among them,SR3 and SR4,which showed enhanced resistance to salt/alkali stress,as well as a vigorous roots and leaves than the parent line JN177,have been authorized as a new salt tolerant variety in Shandong province and declared a new alkali tolerant variety protection to the ministry of agriculture,respectively,which provide suitable materials for exploring the regulation mechanisms in wheat growing development and salinity-alkalinity stress response,and analyzing the correlation between these two mechanisms.In previous studies of our lab,many important genes,such as Tasrol,a saline-resistant QTL candidate gene of SR3,have been identified in combination with the transcriptome analysis of the strain under stress treatment.And the epigenetic modifications such as DNA methylation were also found closely relative to the stress resistance of the introgression lines.However,SR3 developmental regulation mechanism and the relationship with stress response regulation,is still unknown.Therefore,with the data from available transcriptome and miR:NA sequencing,this study analyzed genetic and epigenetic changes of genes associated with saline/alkaline stress response and development in SR3/SR4.And furthermore,the pathway regulated by Tasrol,as well as the detail mechanism of its common function in stress resistance and development control,was focused.And we found that both redox homeostasis and energy homeostasis played important roles in regulation of saline-alkali stress response and growing development,while Tasro1 pathway was the key node contacting these two homeostases.The research results of this work were as follows:1.The transerptome characteristics related to development and saline/alkaline stress response in wheat introgression linesWith transerptome data from gene microarray and Digital Gene Expression(DGE),the expression levels of genes in SR3 and SR4 were analyzed at a whole level.The development related genes were screened through analyzing the altered expression of genes in SR3/SR4 comparing with JN177 under normal conditions,while the stress response related genes were selected by analyzing the differential expression of genes in SR3/SR4 under saline/alkaline treatment.Then the GO clustering analysis for these two groups of genes was did with BLAST2GO,and the GO categories both associated with development process and stress response were found:(1)Redox change.Including many genes relating to ROS producing or scavenging;(2)Energy metabolism.Inclunding genes associated with metabolism of carbohydrate and ATP;(3)Regulation of transcription.Including genes relating to transcription factors and x epigenetic factors.2.miRNAs related to root development or saline/alkaline stress in wheat introgression linesWith the data from respectively sequencing of sRNA and Degradome,many wheat miRNAs and their targets were identified.And then the expression pattern,as well as the regulation network of these miRNAs was analyzed at a whole level.The development relating miRNAs were selected by comparing the miRNA expression level between SR3/SR4 and JN177 under normal conditions.The miRNAs responding to stress were the ones with altered expressions in JN177 under different conditions.And the stress tolerance relating miRNAs were screened with differential expression analysis in SR3/SR4 under saline/alkaline treatment.Furthermore,the GO clustering analysis was made for the target genes and the common categories both relating to development and stress response were also identified:(1)Regulation for redox action and ROS metabolism;(2)Regulation for mitochondria function and ATP metabolism;(3)Regulation for signal transduction,including phosphokinase and phytohormone pathways;(4)Regulation for transcription,including transcription factors and epigenetic factors.3.The key gene and pathway for wheat introgression lines in regulating saline/alkaline stress resistance and developmentAs the QTL related gene of salt stress resistance in SR3,the molecular mechanism of Tasrol regulating stress response and leaf development synergistically was explored.Previous studies showed that Tasrol is not only closely related to the anti-stress phenotype but also positively related to the vigorous growth of SR3,indicating that it may be a regulator between development and stress response.Tasro1,together with its interacting protein TaSIN,could regulate ROS metabolism,thus keeping the redox homeostasis in wheat.In this work,we focused on the control of wheat leaf size regulated by Tasro1-TaSIN,and explored the synergetic regulation of growing development and stress response.The main results were as follows:(1)Tasrol influenced leaf size by regulating cell size,in which the accumulation of ROS might play an important role;(2)Tasrol and TaSIN regulated leaf development antagonistically;(3)As the target of TaSIN,TaBCS1b negatively regulated leaf size;(4)TaBCSlb interacted with TaLETM2,which had reverse effect on leaf size,but no effect on the metabolism of ROS;(5)TaBCS1b and TaLETM2 antagonistically controlled leaf development through regulating energy metabolism and cell cycle.Based on these results,we could conclude that:Tasrol&TaSIN regulated stress response through redox homeostasis while TaBCS1b&TaLETM2 regulated leaf development via energy homeostasis,and the Tasro 1-TaSIN-TaBCS1b-TaLETM2 pathway linked these two homeostases to regulate wheat growing development and stress response antagonistically.Taken together,in this work,with the special wheat introgression strains involving with both development and stress tolerance,we attempted to explore the relationship between developmental regulation and saline-alkaline stress response either by genomic&epigenomic analysis at a whole level or by detail studying for regulatory mechanism of key function genes.As a final conclusion,we considered that the integration of redox homeostasis and energy homeostasis was rather pivotal for the synergetic regulation of saline-alkaline stress response and growing development.Our study could promote the understanding of the relationship between development and stress,deepen the understanding of the interaction between plants and the environment,and provide reference for breeding varieties that take both growth capability and stress resistance into consideration.