The Expression Profiling In The Different Seed Developmental Stages And The Expression Of DGAT From Peanuts

Peanuts are one of the most important edible oil crops in the world. The annual output of peanut in China ranks the first in the world. The peanut oil has always been one of the main edible vegetable oil in our country for many years, and more than 50% of the total output of peanut is used for oil.Peanut oil is mainly composed of oleic acid, linoleic acid and other unsaturated fatty acids and their content is in commonly 80%. It was known as China’s "olive oil". In order to survey and grasp the key genes controlling peanut oil accumulation at the molecular level, we analyzed the seed transcriptome in different developmental stages of different peanut, and research the difference of gene function and genetic structure in critical period of oil accumulation, and excavated the gene regulating high oil. We analyzed the expression of diacylglycerol acyltransferase(DGAT) controling the oil synthesis. The main contents are as follows:1. In this study, the high and low oil peanut varieties were selected to construct 4 transcriptome sequencing library of the peanut seeds in early and late stage, using high-throughput Solexa sequencing platform. A total of 53924092 clean reads was obtained, and the total length was 4853168280 nt. Finally 59236 Unigenes were assembled with a total length of 44505000 nt and the average length of 751 nt.2. The COG functional classifications involved most of the life activity, and the cluster for“general function prediction only” represented the largest group, with 4730 genes. The cluster for“nuclear structure” represented the smallest groups, with 3 genes, and the lipid transported metabolism group had 654 Unigenes. There are 15468 Unigene similar to genes of the database. The genes involving metabolic processes were the most of all with 6028.3. To reference the KEGG database, we annotated Unigene which is in the transcriptome of Regulation of lipid synthesis in peanut seeds. In total, Uingene of the transcriptome were assigned to 126 KEGG pathways, with metabolic pathways, plant-pathogen interaction, plant hormone signal transduction, phenylpropanoid, biosynthesis, lipid metabolism and RNA degradation as so on. Among these pathways, the Biochemical metabolism pathways represented the largest group with 7672 members, followed by plant hormone signal transduction pathways with 1493 member. 4 kinds of metabolism pathways were related to Lipid, which are Fatty acid metabolism pathway with 145 genes, fatty acid biosynthesis pathway with 85 genes, unsaturated fatty acid biosynthesis with 116 genes and alpha-linolenic metabolism pathway with 138 genes.4. To analysis unigene expression for two each library and we classified these different expressed genes into 120 metabolic pathways. There were 5 metabolic pathways have a tight link with Lipid synthesis, which are unsaturated fatty acid biosynthesis, linoleic acid metabolism, alpha-linolenic metabolism, atty acid biosynthesis, fatty acid metabolism.5. We mapped these differential expressed genes to the reference canonical pathways in KEGG and found that the great mass of genes were down-regulated. The analysis shows that genes regulating fatty acid synthesis in the preliminary stage were active, and the speed of fatty acid synthesis and Lipid synthesis slow gradually with the expression level of related genes falling.6. The differential expressed genes are almost key enzyme and rate-limiting enzyme in lipid metabolism, and we also found five Unigenes coded for diacylglycerol acyltransferase, which catalyzed the final step in the TAG biosynthesis pathway. We analyzed the five gene sequence of DGAT from peanut with bioinformatics methods and found that they belong to diacylglycerol acyltransferase Ⅰ(DGAT1). We analyzed the relative quantitative expression of 5 DGAT genes in different times by the Real-Time RT-PCR method. The results indicated that the expression of diacylglycerol acyltransferase(DGAT) gene was significant difference. We hypothesized that the different expression of Ah DGAT in different development stages of peanut seed is one of an important determinant of the effect of oil content in Peanut.