Preliminary Idetification Of Biological Functions Of SlEXPA3 And SlFRK2 In Tomato

Tomato(Solanum lycopersicum)is the most commonly grown vegetable in the world and is well accepted by people for its high nutrient value and particular flavour.Tomato also becomes a model plant for researching fruit growth and development,because of its short life cycle,aboundant genome information and convenience for genetic transformation.Although tomatoes in the market at present exhibited prolonged shelf life,consumers still complain their poor flavors.Sugar content of tomatoes is one of the major factors that controlling the fruit flavors.It is a time-consuming work to improve the sugar content of tomato fruits using traditional breeding methods.In comparison,it is a preferred choice to map and clone the major genes controlling tomato fruit sugar content,and then to use them to improve tomato fruit flavors through molecular marker assistant selection or genetic engineering.However,the deficiency of germplasm with high sugar contents in cultivates tomatoes and the limited knowledge of the mechanism of sugar accumulation in fruits restricted its application.Previously,through genome-wide association study and Super-BSA techenologies,we identified two sugar content QTLs in a Solanum pimpinellifolium(TS-21),the candidate genes were also selected in these regions,including one expansin gene and one fructokinase gene.In this research,the transcription profiles of tomato expansin and fructokinase gene families were analyzed,and the preliminary fuctional identification of SIEXPA3 and SlFRK2 were also conducted through genetic transformation method.In general,we mainly got the following results:1.According to the transcriptional prefiles,SlEXPA7,SIEXPA3,SlEXPB8,SlEXPA11,SlEXPLB2 and SIEXPLB1 were selected to check their biological functions.Vector construction and genectic transformation of tomato about these genes were conducted;2.Most of the transgenic plants that overexpressing or knock down of the selected expansin genes were died,only the SIEXPA3 overexpression transgenic plants were survived well,which were used as the material for functional identification;3.Compared with the wild type,SlEXPA3 overexpression transgenic lines(L3-2 and L3-6)become shorter,the length of internode and the angle between leaf and stem were significantly reduced.Transgenic lines also exhibited a higher leaf green colour and higher net photosynthesis rate under higher photon flux density(800-1500 μmol/m2/s);4.Compared with the wild type,some GA synthesis genes and some genes related to ABA signal transduction modified their expressions in SlEXPA3 overexpression transgenic lines5.Phylogenetic relationships among members of each gene families of hexokinase,fructokinase and phosphofructokinase were analyzed.Together,their expression profiles in different organs,as well their expression patterns under the treatments of exogenous phytohormones and different abiotic stresses were also checked.These genes exhibited different spatiotemporal and inducible expression patterns;6.S1FRK2 knock down transgenic lines were created through Agrobacterium-mediated transformation method,using both S.lycopersicum A57 and S.pimpinellifolium TS-21 as receptor materials.Fruits of these transgenic T0 plants showed lower total soluble solid contents than those from their corresponding wild type.