Resource Allocation And Gene Expression Profiling Of Vicia Faba L. And Zea Mays L.under Persistent Pollution Of Pb,Cd

Over the past decades, emissions of toxic heavy metals released into the environment have risen sharply with the development of industrial production. When toxic heavy metals are taken by plants, heavy metal ions interferes with plants’ physiology and metabolism, which leads to structure disruption or activity inhibition and finally affects the resource allocation of plants.In this study, RNA-Seq (Quantification) method have been used to identify Pb, Cd stress responsive genes functioning in resource allocation, to further elucidate molecular mechanisms of tolerance in faba bean and maize, which were cultivated in the field polluted by Cd (10mg/kg,60mg/kg), Pb (40mg/kg,250mg/kg) and the combined treatment of Cd and Pb (Cd20mg/kg+Pb60mg/kg). The results were showed as follows:(1) Pb and Cd had significant inhibition effect on the growth of faba bean and maize, while had a promotion effect on the quantity or quality of seeds. There were different quantitative results based on different variety and concentration of pollutions. For the trait of vegetative growth, the heavy metal pollution lead to the brachysm of faba bean and maize population, and the stongest inhibit effects were presented in highest concentration. At the same time the stem dimension and root length of faba bean and maize decreased.For the trait of reproduction, three varieties of faba bean showed ecological difference on adaptive strategy, such as A and C decreased the number of seeds and improved the quality of seed to guarantee the competitiveness of descendants, but variety B increased both the number and the weight of seed. For the maize, var. Z1and Z2increased the weight of seeds, while it was reduced in var. Z3.(2) Pb and Cd had significantly changed the resource allocation pattern of faba bean and maize. For the biomass allocation, heavy metal pollution generally reduced the total biomass of faba bean and maize. In generally, plants reduced the stem leaf investment, and improved the reproductive and root investment when they responsed to heavy metal pollutions.As for energy allocation, faba bean and maize had improve the total calorific value of the plants. The calorific value of leaves and seeds of faba bean was increased with the concentration of treatment. While the calorific value of the stem and root was increased firstly and then decreased with the increase of concentrations, however, it was still higher than the control, which suggested that the higher calorific value might be represented the adaptability of faba bean to the heavy metal pollution. For the maize, calorific value of leaves slightly increased when it was under the low dose, while, with the increased of concentration, it was decreased obviously.(3) The results of resource allocation and RNA-seq showed that, Pb, Cd pollution induced the biosynthesis of secondary metabolites (energetic compounds) of Vicia faba var. A, which might be the reason of the increased gross calorific value of faba bean under heavy metal pollution. Moreover, maize has same strategy responding to heavy metal pollution. But with the increase of the concentration of pollution, by reducing the growth of corn is not enough to maintain the balance of energy. To maintain the reproductive energy balance, maize reduced the energy reserves of vegetative organ, which resulted in the lower total calorific value and relatively increased the reproductive investment.(4) RNA-Seq (Quantification) results showed that under the heavy metal pollution, gene expression is extremely different between the treatment and the control of faba bean and maize. The DEGs were mainly enriched in ion transport, metal ion binding, antioxidant activity, oxidoreductase activity fuction froups. Moreover, DEGs were significantly enriched in secondary metabolite biosynthesis and metabolism pathways and signal transduction There is some common Pathways between Cd and Pb treament, including the plant hormone signal transduction, flavonoid biosynthesis, phenylpropanoid biosynthesis, stilbenoid, diarylheptanoid and gingerol biosynthesis, pentose and glucuronate interconversions, glycerophospholipid metabolism, starch and sucrose metabolism. In these pathways, the up-regulated DEGs of faba bean were basicly far larger than the down-regulated DEGs, which implied that these Pathways might be related to the mechanisms tolerance in plant.(5) According to the results of RNA-Seq (Quantification) of faba bean and maize, we screened the genes which could related to resistance of plant to Cd and Pb.