Expression Of Sulfur Uptake-and Assimilation-related Genes In Response To Cadmium, Bensulfuron-methyl And Their Co-contamination In Rice Roots

With the development of modern industry, environment pollution has become more and more serious. Industrial and domestic sewage for irrigating, excessive use of fertilizer have led soil heavy metal pollution aggravated; too much use of pesticides and the residues of them in soil have also become the main organic pollution. Bensulfuron-methyl (BSM) is a sulfonylurea herbicide that is widely used in paddy fields; Cadmium (Cd) is now one of the main heavy metal pollutants to soil, moreover its toxicity and mobility are both strong. So they have become serious threat to our country soil environment, influencing the rice quality and human health. In the present study, Two rice (Oryza sativa L.) cultivars, YueXiangzhan and FengMeizhan (both Indica rice), were analyzed. Either CdCl2or BSM was added to the culture solution for the treatments of Cd (45μmol/L Cd2+), BSM (0.25μmol/L BSM) or Cd+BSM (45μmol/L Cd2++0.25μmol/L BSM), and an equal volume of water was added to serve as the control (CK). The present work focuses on the effects of S uptake-and assimilation-related gene expression in rice roots in response to Cd, BSM and their co-contamination using microarray and quantitative real-time PCR technology. The main results were summarized as follows:1. The effect of Cd, BSM and their co-contamination on rice growthCompared to the control, the Cd, BSM and Cd+BSM treatments significantly inhibited the increase in root length, shoot height, shoot dry weight and root dry weight of FengMeizhan and Yuexiangzhan seedlings after20d, thereby indicating the inhibited growth of the seedlings. And the Cd+BSM combined treatment alleviated the toxic effects of Cd or BSM single treatments on FengMeizhan seedlings, which was not observed on Yuexiangzhan seedlings. Moreover the treatments caused peroxide stress in the roots of both cultivars. 2. The Influences of Cd, BSM and Cd+BSM treatments on S content in rice seedlingsCompared to the control, Cd and Cd+BSM treatments promoted sulfate absorption in both cultivars and that BSM also promoted sulfate uptake in YueXiangzhan specimens. Moreover, Cd+BSM promoted greater sulfate absorption by FengMeizhan seedlings. This may represent one of the mechanisms by which Cd+BSM treatment alleviates Cd toxicity in FengMeizhan seedlings.3. Differential expression of sulfate uptake-and assimilation-related genes determined by microarray and verified by QRT-PCRThe microarray analysis demonstrates that Cd and Cd+BSM promoted sulfate uptake by inducing the expression of sulfate transporter and permease genes (such as HSAT、ST3.1、ST4.1、SP) in rice roots. Cd and Cd+BSM induced the gene expression a series of sulfate assimilation-related genes, such as ATPS、CBS、CS、PR、RD-like et.al., thereby activating the sulfate assimilation pathway. Cd+BSM treatment induced the gene transcription of sulfur uptake-and assimilation-related genes to a greater degree than BSM and Cd treatments.Cd+BSM, alleviated the Cd toxicity in FengMeizhan seedlings. Genes which encoding the increase of heavy metal chelates, PCs and MTs and GSTs and antioxidation were also induced by Cd and Cd+BSM treatment.As displayed by the QRT-PCR results, the transcriptional levels of most selected genes correlated with the expression analysis detected by the microarray. The QRT-PCR results further verified that Cd and Cd+BSM can improve the transcription level of sulfate uptake-and assimilation-related genes, promote sulfur absorption and assimilation in rice seedlings, increase PCs, MTs, GTSs, allieviate the toxicity of Cd, BSM to rice, improve the resistance of the rice to combined pollution.