Fine Mapping And Candidate Gene Analysis Of A Cucumber Leaf Yellowing Mutant Gene Yf

Cucumber?Cucumis sativus L.?leaves are important organs of photosynthesis and an important basis for plant morphogenesis and fruit growth Cucumber leaf color often mutates under natural conditions or artificial mutagenesis.Therefore,people often use leaf color mutation to study related genes and their mechanism of action,which is of great significance for the identification of cucumber leaf color related genes and even photosynthesis.In this experiment,the yellow-green leaf color mutant yf of cucumber was used as the research object,and the leaf color and related phenotype microstructure observation were analyzed.The F₂ segregating population was constructed with GY14,and the molecular markers closely linked to the candidate genes were screened by BSA.The cloning of the candidate genes laid the foundation.Below are key research findings:1.The pigment content,photosynthetic performance and photosynthetic related content of cucumber leaf yellow mutant yf were determined.The chlorophyll content of the mutant cotyledon,seedling and seedling stages was at a low level.In the seedling stage and seedling stage,the net photosynthetic rate?Pn?,intercellular carbon dioxide concentration?Ci?and minimum initial fluorescence?F0?of the mutant were significantly lower than Gy14,and the non-photochemical quenching coefficient?NPQ,qN?was significantly higher.On Gy14.The5-aminolevulinic acid?ALA?content in the chlorophyll synthesis pathway in Gy14,Mg-protoporphyrin IX?Mg-Proto IX?,coproporphyrinogen III?Coprogen III?and protophyll chlorophyllate?Pchlide?were significantly lower On Gy14,but the content of Proto IX is not much different from Gy14.2.The microstructure and ultrastructure of mutant yf leaves were analyzed.Microstructural analysis showed that the mutant palisade tissue arrangement was scattered and the cell gap was large.Transmission electron microscopy analysis showed that the mutant sponge cells were irregular,the deformed cells were more,the cell wall was thin,the inclusions were less,and the intercellular gap was large.The chloroplasts in the cells are different in size,with more malformed chloroplasts,and the chloroplast does not contain or contain a small amount of starch granules.The granules of the thylakoids in the chloroplast are thin,linear and arranged in disorder.3.The inheritance of leaf yellow in the yf×Gy14 F₂ population was analyzed.The green and yellow strains showed a 3:1 segregation in the yf×Gy14 F₂ segregating population,indicating that the leaf yellow mutation is a recessive mutation controlled by a single gene.4.Localization of yf genes and prediction of candidate genes.Four SSR markers located on chromosome 7 were screened by BSA method,and the yf gene was mapped between primers SSR20583 and SSR10066 primers.Further screening of 593 F₂ isolated isolates revealed that 8 exchanged plants were generated between SSR10066 and the target gene,and the yf gene was mapped between SSR20583-SSR10066,and the genetic map distance was 2.3 cM and 4.5 cM..By comparison with genomic information,there are 41 genes in SSR20583-SSR10066,among which Cucsa.099260 is related to thylakoid synthesis,which is presumed to be related to leaf yellow mutation.Amplification of the CDS region of Cucsa.099260 of Gy14 and yf mutants,no mutation sites were found.5.Candidate gene expression pattern analysis.In the leaf yellow mutant,the expression level of the candidate gene Cucsa.099260.1 was reduced by 526 times,and the relative expression of the mutant glutamyl-tRNA reductase?Glu-TR?was decreased by 0.59 times.The Mg chelatase H subunit gene(The expression of MgCH-H was increased by 26.59 times,the expression of chlorophyll synthase gene?CS?was decreased by 0.23 times,the expression of protophyll oxidoreductase?Por?was decreased by 0.30 times,and the expression of chlorophyll b reductase gene?CBR?was increased by 1.63 times.