The Study Of Regulation Mechanism Of Gene Expression For Populus × Euramericana(Dode) Guineir ‘Neva’ Under Cd Stress

With the development of modern industry, soil contaminated by heavy metals poses a threat to human health and life quality, has become increasingly the world wide environmental problem. Phytoremediation of heavy metal polluting soil is one of the important way to make soil contaminant nontoxic. Compare other technology, plant restore technology have economy, high-powered, green cleanse and isprone to disposal afterward. It show favorable zoology economy, society benefit and haveexpansive application foreground. With the Solexa transcriptome sequencing technology, transcriptome of Populus×euramericana(Dode)Guineir ‘Neva’ was studied under the conditions of cadmium stress of 100 mg/kg and 200 mg/kg for 40 days and 80 days. The objectives are to investigate the influence of cadmium stress on gene expression changes of Populus×euramericana(Dode)Guineir ‘Neva’, to understand the molecular mechanism of Populus×euramericana( Dode) Guineir ‘Neva’ responding to cadmium, and provide theoretical guidance for restoring polluted soil with cadmium by Populus×euramericana(Dode) Guineir ‘Neva’ as restoring species to restore cadmium pollution in soil by combining the outcome of physiology and biochemistry under cadmium stress of Populus×euramericana(Dode)Guineir ‘Neva’. The main conclusions are as follows:(1) 204,417 unigenes were obtained from eighteen samples of root, stem and leaves of Populus×euramericana(Dode)Guineir ‘Neva’ using Solexa technology, among which 166,336 unigenes had matching homologous proteins, in addition, 116,267 unigenes were noted at 22,231 GO terms on 14 floors, as well as 88,006 unigenes were annoted at 25 COG functional categories. Of 36,804 unigenes 277 pathways were mapped 2,642 repeat base unit types and 88,691 SSRs were founded among 204,417 unigenes.(2) Under cadmium stress, 2580 enrichment GO terms of differential genes were founded in Populus×euramericana(Dode)Guineir ‘Neva’. The number of GO terms from roots was larger than that from leaves, while the number of GO terms from leaves was larger than that from stems. GO terms from leaves and stems got higher with the increment of cadmium concentration GO terms from roots became lower by contrast. In particular, on the 80 th day, nevertheless, with the time of cadmium stress been longer, enrichment of GO terms from leaves and stems decreased, and enrichment of GO terms from roots increased when the concentration of cadmium was low. The enrichment of GO terms were made of enzymes, which involved in main metabolic pathways, the synthesis and catabolism of biological molecules, the process of responses and combine to stimulates, the process of translate, transcribe, signal path, control and regulation and other physiological and biochemical pathways.(3)Under cadmium stress, 448 obvious enrichment pathway terms of differential genes were founded in Populus×euramericana(Dode)Guineir ‘Neva’.The number of terms from roots was larger than that from leaves, while the number of terms from leaves was larger than that from stems. With the cadmium stress time prolonged, enrichment of pathway terms from leaves and stems decreased. Enrichment of pathway terms at roots increased when the concentration of cadmium was low. Pathway terms from leaves and stems got more with increment of the cadmium concentration. Pathway terms from roots increased on the 40 th day, nevertheless decreasing obviously on the 80 th day. The enrichment of pathway terms involved in the synthesis and catabolism of biomacromolecule and secondary metabolite, receptor and signal system, photosynthesis, respiration and other physiological and biochemical process.(4)Under the cadmium stress of 100 mg/kg, leaves of Populus×euramericana(Dode)Guineir ‘Neva’ showed some adaptability, photosynthetic organ and relevant transcription activity were increased. Cadmium stress could seriously destroy the antioxdant system of plants, fortunately, active copings happened in Populus×euramericana(Dode)Guineir ‘Neva’ with glutathion peroxidase, glutathione transferase, and the synthesis and combination of glutathione. Under the cadmium stress of 200 mg/kg, Populus×euramericana(Dode)Guineir ‘Neva’ were seriously destroyed. First, net photosynthetic rate decreased obviously, mainly due to the break of photosynthetic organ, the damage of photosynthetic system, the inhibition of enzyme activity, the effect of carbon fixation, electron transfer and stomatal regulation. Second, nitrate, amino acid and the activity of related enzymes decreased and destroyed ionic equilibrium by influencing the activity of potassium channel. At last, cadmium stress could seriously destroy the antioxdant system of plants, would decrease peroxides and biosynthesis pathway of peroxide, ascorbic acid and vitamin E.(5)Cadmium stress could influence Populus×euramericana(Dode)Guineir ‘Neva’ on response to other stimulate either promoting or weakening. Specifically, with the similarity of electron configuration of cadmium and zinc, responses of leaves to cadmium and zinc were synchronous under the cadmium stress. cadmium destroyed cytoderm of plants, decreasing cytoderm modification, activity of enzyme and synthetic process of biomacromolecule but increasing its decomposition.(6) Cadmium stress could increase Populus×euramericana( Dode) Guineir ‘Neva’ pathways about flavone and flavonol biosynthesis, however we were not see the same phenomenon with root under the cadmium stress on the 80 th and leave under the cadmium stress of 200 mg/kg on the 80 th day, This showsed that under cadmium stress for a long time could decreases the ability of Populus×euramericana(Dode)Guineir ‘Neva’ to respond to cadmium, the influence follows the sequence: root,stem and leaf.