The Cadmium-induced Responses Of Eggplant (Solanum Melongena L.) Root Stock Solanum Torvum

Solanum torvum L. is usually used as root stock for eggplant(Solanum melongena L.) in modern agriculture, and S. torvum resists against Ralstonia solanacearum, Verticillium dahliae and Fusarium oxysporum f. sp. melongenae. Graft eggplant onto S. torvum can effectively resist these soil-borne diseases. Solanum torvum is a low Cd-accumulating plant. Its plant can effectively block Cd transportation from the roots to the shoots. Therefore, the Cd concentration in the scion fruits reduced in the same time, and avoid the heavy metal induced harm after human and animal eating them. So far, many studies regarding the molecular mechanisms of Cd hyperaccumulation have been reported; however, there has little study on Cd toxicity, including any low Cd-accumulating species. Studying the molecular mechanisms that are responsible for low Cd accumulation in plants can help people to reduce or avoid heavy metal. These results form a basis upon which to further explore the molecular mechanisms of Cd accumulation and tolerance, and provide an insight into novel strategies that can be used for phytoremediation and food safety.In this study, we compare Cd tolerance and accumulation between the low Cd accumulator.S. torvum and the Cd accumulator S. nigrum. We investigated the molecular mechanisms that are responsible for Cd tolerance and accumulation using a combination of transcriptome, physiological and proteomic analyses.1. To elucidate the mechanisms underlying the differential Cd accumulation in S. torvum and S. nigrum, we investigated the transcriptional regulation profiles in the two Solanum species roots using a tag-based DGE system. To verify the DGE studies by using an independent experimental approach, semiquantitative reverse transcription (RT)-PCR and RT-qPCR analyses were performed for selected genes. The differential expression genes involve in heavy metal transport and detoxification, antioxidant-related genes, and metabolic processes. Ns-Hbl, peroxiredoxin-2E, and some other antioxidant-related genes up regulated higher in S. nigrum than S. torvum. The graft experiment confirmed that the Cd content of the scions largely depended on the rootstocks, which suggests that both the Cd uptake capacity in roots and the differential Cd loading capacity into the root xylem are responsible for the differential Cd accumulation between S. nigrum and S. torvum. High expression of IRT2, ZIP11, and COPTS in S. torvum roots may promote Cd into the vacuolar or endomembrane systems, thereby increasing root Cd sequestration and reducing Cd transport from the roots to the shoots.2. For comparison of Cd tolerance in the two species, the study used physiological measurements to investigate the oxidative damage, antioxidants and antioxidant enzyme. The ROS data proved that the tolerance ability of S. torvum is lower than S. nigrum. Compared the antioxidant enzyme activity and found that S. nigrum enzyme activities increased higher than those of S. torvum. The Cd induced SOD, CAT, APX and POD activity increased in leaves and root of S. torvum,but reduced the GR activity in the S. torvum roots only.3. To obtain the molecular mechanisms of S. torvum and S. nigrum in response to Cd stress, two-dimensional gel electrophoresis (2-DGE) was utilized to compare the proteins in S. torvum and S. nigrum in control and Cd-treated plants. Using the MALDI-TOF/TOF MS analysis to identify the spots changes more than 2 folds. These proteins are involved in phytohormone synthesis, defense responses, energy metabolism, and cytoskeleton construction. Here, the study found the changes of several proteins in 5. torvum and S nigrum are the same. S-Adenosylmethionine synthetases are up-regulated with Cd treatment, indicated that the two plants improve resistance by ethylene pathway. Our study indicated that Cd induced the energy metabolism both of the two plants. Our data showed that, Cd induced the ADH up-regulated in S. torvum roots, and induced the sulfate adenylyltransferase and 2-phosphoglycerate dehydratase up-regulated in S. nigrum roots. The two plants increase their metabolism to resist Cd for survival.