Study Of Gene Expression Profile For Soybean Seeds At Different Development Stages

Soybean (Glycine max (L.)Merrll.) is one of the most important oil crops and also one of the most important economic crops in the world. Soybean contains rich proteins, lipid and various materials which are beneficial to human. It is the main sources of proteins, greases and raw materials of food and feed.The quality of soybean is the basic principle for its processing and utilization, while oil and protein composition of soybean are the two main factors of its quality. There are about18%-27%of lipid and40%protein Soybean seeds contain. More than90%of the lipid composition is fatty acid, and the majority of protein components is a variety of amino acids and storage protein.As the rapid development of genetic engineering and molecular biology techniques, the improvement of these two nutrients content and composition has always being the focus of scientists. However, the physiological processes of lipid and protein biosynthesis are very complex, especially the protein contains lots of amino acids. Majority of these amino acids has their own different pathways which many genes and enzymes are involves in. For these genes and enzymes, it is uncertain their action sites and the period of their action and how to make the various components of the cell changes. So, genetic engineering improvement of soybean seeds quality should choose an efficient and high-throughput method for the overall monitoring so as to discovering the key regular genes.Innovation:Gene space-time expression has become the hot spot, and the expression of genes is reflected by space-time and some other factors. Compared with the static genome, gene expression always presents a complex dynamic process. Gene expression profiling analysis is just the method that analysis gene space-time expression to detect the complex physiological processes. Solexa (Illumina) is the second geneRation platform as the new large-scale, high throughput sequencing. It has a larger wider range and higher resolution than microarray. So in this study we selected Solexa digital gene expression profiling sequencing to detect the soybean seeds at four different stages.15DAF was taken as control, and compared with the subsequent three stages of the gene expression from mRNA levels. This is the first comprehensive and accurate detection for the key genes that regulated lipid and protein biosynthesis.The main results are as follows:1. By Solexa sequencing, a total of29632,29511, and29572differentially expressed unigenes were detected. Of them,11592,16594and16255differentially expressed unigenes matched the conditions of the FDR<0.001and|log2Ratio|≥1, respectively.9905differentially co-expressed unigenes were in common, and these unigenes can be identified as the key genes during the soybean seeds development.2. By Gene Ontology analysis, a total of11963genes contained at least one functional annotation. The majority of these genes’function were concentrated in the binding and catalytic activity of the molecular function ontology, of cell parts, the cell and organelles of cellular components, and they mainly involved in cellular and metabolic biological processes. The GO function classification models are similar in these three compare groups.3. During the GO analysis of fatty acid and lipid synthesis, a total of112differentially co-expressed genes were filtered out in these three groups. While in the analysis of methionine and other amino acids biosynthesis, a total of159differentially co-expressed genes were filtered out in these three groups.4. In this study, a total of124pathways were identified by Solexa sequencing, in which11228differentially expressed genes are annotated, and five lipid and amino acid biosynthesis pathways were filter out.5.25differencially co-expressed genes were identified in fatty acid synthesis pathway in the three groups, and a total of,86co-expressed genes in amino acid anabolic metabolism pathways.6. Seeds of55DAF were randomly chosen as the sample for RNA-extraction and12differentially expressed genes were selected to analyze their expressions using qRT-PCR. The results were consistent well with those obtained from Solexa sequencing.These results provided a molecular biology background for soybean seeds development especially provided a comprehensive and detailed information for lipid and protein biosynthesis during development of soybean seeds. All of these genes identified in our research can be the important resources for high-quality soybeans breeding.