DGE Method Research Of Seed Germination And Postgermination Period In Populus Simonii×Populus Nigra

Populus simonii×Populus nigra is a lofty arbor, which belongs to Salicaceae and Populus, and it is a vanward species of afforestation in mountain waste and wasteland and a famous industrial timber species. The study of Populus simonii×Populus nigra mainly focuses on ecology, silviculture and breeding. But little is known about the seed germination of Populus simonii×Populus nigra in molecular mechanism.Most flowering plants reproduce by seed for multiplication with sexual reproduction. Seed germination is the transition of the quiescent embryo into a new photosynthetically active plant. Germination is a complex physiological and biochemical process during imbibed mature seed to seedlings in a rapid conversion and prepare for seedling growth. Because of its susceptibility to injury, disease and so on, germination is considered to be the most critical phase in the plant life cycle. It is one important issues of plant cell biology to study the molecular mechanisms of seed germination. The emergences of genomics provide a good means for studying the mechanisms of seed germination in recent years. At present, except on model plant Arabidopsis and other minority of model plants and crops, few works have been performed on Populus which is as an important mode of woody plant. The genomics research on Populus simonii×Populus nigra seed germination has very important significant not only for exploring the mechanism of germination and improving seed biology research but also for deeply understanding of molecular genetics of complex genomic plants. It also has great value for guiding breeding work.In this study, we identified Populus simonii×Populus nigra seed-specific/preferential genes and differentially expressed genes in Populus simonii×Populus nigra seed during germination via DGE. The main results are listed as follows:(1) By comparing the DGE of Populus simonii×Populus nigr mature seed with ten-day-old seedling, we identified1789genes specifically or preferentially expressed in Populus simonii×Populus nigr mature seed. Through our analysis of these1789genes in abundance, family number, and GO enrichment, we found that most of them were involved in lipid metabolic process, transport, redox, ATP synthesis, hexose metabolic process, Golgi vesicle-mediated transport and transcription factors. We speculate that the genes specificially expressed in seed of Populus simonii×Populus nigr might be involved in the regulation of seed germination in early phase.(2) Through comparison mature seed, rapid water-uptake phase, slow water-uptake phase, radical elongation phase and postgermination phase expressed genes, we obtained6496differentially expressed genes. These genes were divided into12clusters according to their expression patterns, and most of them were involved in cell skeleton organization, cellular polysaccharide metabolic process, transport and protein degradation, amino acid activation and oxidative phosphorylation. These genes may play important roles during seed germination in Populus simonii×Populus nigr.(3) Genes enriched in translation and oxidative phosphorylation pathways and other biological processes in the Populus seed germination is express in high level in most of the germination process, and these genes may play a key role in Populus simonii×Populus nigr seed germination.(4) Genes expression related polysaccharide metabolism, lipid metabolism-related genes, photosynthesis, as well as single-carboxylic acid metabolism was significantly increased only in one or two periods, these results show that these genes play a regulation role in thePopulus seed germination in a specific period in the Populus seed germination.(5) Analysis of the differentially genes expressed in the whole germination,64pathway were enriched significant and belongs to21different metabolic pathways and respectively occurred in different periods; Futher analysis the enriched differential gene in adjacent period show that these gene involved pathway related respiration, storage the substance decomposes synthesis and cell raw material as well as nucleic acid metabolism.(6) To test the respiration rate, protein content, DNA content, amino acid content and soluble polysaccharide content, the results shows that there are two period, rapid water-uptake phase and radical elongation, that seed storage substances changes rapidly during seed germination, while respiration rate in both periods also significantly changed.(7) Analysis of the rate-limiting enzyme coded by the gene family that effect respiratory strength, protein content, DNA content, amino acid content and soluble polysaccharide content, the results showed that there are some relevant between21genes belong to storage material decomposition rate-limiting enzyme in transcriptional level and physiological changes.In conclusion, a large number of genes involved in seed germination were identified through DGE analysis of six different experimental samples in Populus simonii×Populus nigr. Some of them have been found to function in reproduction. We also found a number of novel candidate genes that may play roles in the process. Our results provide a basis for further analysis of seed germination in Populus simonii xPopulus nigr.In the study we got a large numbers gene invoved in the process of seed germination of Populus simonii×Populus nigr, these genes not only contains a large number of known genes, more important is also include many novel genes. These genes will largely contribute to study of the molecular mechanism of seed germination process on genetics and molecular biology.