Prelininary Study Of Arabidopsis Transeription Factor GIS,GIS2 And SPT On Growth And Development Regulation

Transcription factors are proteins that regulate the transcription level of genes in living organisms,and modulate vital processes such as organ development,biochemical metabolism,and physiological reactions in organisms.As an integral part of evolutionary history,plants have evolved a distinct habit from animals,and their transcription factors also evolved over a period of time to develop a series of new plant-specific super-families with unique motifs.The plant transcription factor GIS,GIS2 and SPT act as key regulators in plant development.In accordance with our previous researches on theses genes,we mainly focused on the genes that are the direct targets of GIS and GIS2,analyzed their expression patterns using molecular biology methods,characterized their function by gene-engineering methods,and investigate their roles in trichome initiation and stress responses.In addition,we also investigated the role SPT played in control of seed size and seed reserves storage composition.The main results are as follows:1.The transgenic lines for target genes of GIS had been generated to verify their functions in trichome differentiation,salt and osmotic stress responses.Our results demonstrated that overexpression of At3g04720(PR4)and At2g05160(AtCCCH18)could induce trichome intitiation,and enhance salt and osmotic stress tolerance in Arabidopsis.While At3g57920(SPL15)inhibit trichome development and reduces salt and osmotic stress tolerance.The tissue specific expression pattern of GIS and its target genes indicates that GIS regulates trichome development mainly through targeting SPL15.Furthermore,our results also indicated GIS may involved in abiotic stress responses.2.Based on the phenotypes of transgenic lines of GIS2 target genes in trichome development and stress response,our results demonstrated that over expression of At5g24150(SQE5)promote root development in Arabidopsis,and loss of function of SQE5 reduces trichome number on sepal and infulorence stems.Loss of function of At4g35770(SEN1)made the plant more vulnerable to salt and osmotic stresses,and overexpression of SEN1 reduces trichome number on sepal and infulorence stems.Combined with the temporal and spatial expression pattern of GIS2 and its target genes,our results showed that GIS2 and their target genes are not only involved in regulation of trichome development and stress response,but also in circadian clock and light response pathway.3.The phenotype of spt mutant and overexpression line,demonstrated that the SPATULA(SPT)not only affect the inflorescence architecture but also the flowering time and plant height.In seeds,the loss of function of SPT significantly increased seeds size,reduced oil content,and darken seed coat,but overexpression of SPT only elevated the seed oil content without size change.Ultrastructure analyses revealed that the modification of seed oil content by SPT was mainly through alteration of oil body number and aleurone grain size in seed embryo cells.Our qPCR results demonstrated overexpression of SPT can significantly induce the fatty acid biosynthesis and the expressions of lipids associated TFs,and inhibit the expressions of seed storage protein biosynthesis,transportation gene and associated TFs.These results suggested SPT regulates seed oil content through regulating the expressions of fatty acid biosynthesis and lipid associated TFs.In this study,our result not only extended the knowledge about the roles of plant transcription factors GIS and GIS2 in plant development but also elucidate the SPT funtction in seed oil content control.Our results also provided an important insight into the SPT funtction in seed oil content which can be utilized in future research for high oil crop breeding.This study will be important for us to understand the genetic regulatory networks of trichome development,stress tolerananceand crop breeding,and will benefit for theoretical researches and practical application in the future.