| Ulmus pumila L.is one of the most important native tree species in China,which is widely distributed.After long evolution and thousands of years of artificial cultivation and breeding,U.pumila has been developed into many varieties.There were a large range of diseases and insect pests,which led to the gradual elimination of elm from the list of afforestation in recent 20 years.The germplasm resources of elm are constantly lost,and the genetic basis is less and less.Therefore,in this experiment,the important part of the elm reproductive system of samara was the study material.We collected the seeds of elm fruit and explored the variation of the actual phenotype of elm species in 31 regions in China.Based on SSR molecular markers,we analyzed the genetic diversity and genetic structure of U.pumila in Shandong Province,and analyzed the transcriptome of U.pumila fruit to identify plant nutrient related genes and fruit development pathway.The main conclusions are as follows:1.In 2018-2019,we collected 214 high-quality U.pumila germplasm resources in nine provinces in China.The phenotypic diversity of 247 U.pumila fruit and seed resources in 31 areas was studied by using the existing U.pumila fruits in the laboratory as materials.The results showed that there were significant differences in 9 phenotypic traits of U.pumila fruits and seeds from 31 provenances,and the coefficient of variation was 4.848%-22.959%,with an average of 11.499%.The variation coefficient of fruit phenotypic traits was greater than that of seed phenotypic traits.The variation of fruit morphology of U.pumila was greater than that of seed morphology,and the variation of fruit morphology of U.pumila was more abundant.The phenotypic traits of U.pumila were significantly correlated with altitude,annual precipitation and annual temperature.The phenotypic traits of U.pumila were significantly correlated with altitude,annual precipitation and annual temperature.The fruit and seed morphology of U.pumila has certain correlation with geographical and climatic factors.2.The research on genetic diversity showed that the level of genetic diversity of U.pumila was high,the average number of alleles(Na)was 2.762,Shannon diversity information index(I)was 0.779,observed heterozygosity(Ho)was 0.550 and expected heterozygosity(He)was 0.471.Genetic differentiation studies showed that 96% of the genetic variation came from within populations,and only 4% of the genetic variation came from between populations.3.In this study,high-throughput RNA sequencing was performed in U.pumila edible fruits and leaves and 11,386 unigenes were filtered as dysregulated genes in fruit samples,including5,231 up-and 6,155 down-regulated genes.Hundreds of pathways were predicted to participate in seed development and phytonutrient biosynthesis in U.pumila by GO,Map Man,and KEGG enrichment analysis,including ‘seed maturation’,‘glycine,serine,and threonine metabolism’ and‘phenylpropanoid biosynthesis’.ABA-mediated glucose response related ethylene activated signaling pathway(e.g.,ABI4)were supposed to associate with elm fruit development;unsaturated fatty acids pathway(e.g.,ACX2 and SAD)were predicted to participate in determination of fatty acid composition in elm fruit;flavonoid and coumarins biosynthesis(e.g.,CYP98A3 and CCo AOMT1)were demonstrated to correlate with the bioactivity of elm fruits in human cancer and inflammation resistance.To provide more information about fruit developmental status,the q RT-PCR analysis for key genes of ‘phenylpropanoid biosynthesis’ and ‘alpha-Linolenic acid metabolism’ were conducted in samples of young fruits,ripe fruit,old fruit,and leaves.Two biosynthetic pathways for unsaturated fatty acid and Jasmonic acid(JA)were deduced to be involved in fruit development in U.pumila and the phenylpropanoid glycoside,syringin,was speculated to accumulate in the early development stages of elm fruit.Our transcriptome data supports molecular clues for seed development and biologically active substances in elm fruits. |
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