Metabolic engineering of Oryza sativa for complete biodegradation of thiocyanate.

Industrial thiocyanate (SCN-) waste streams from gold mining and coal coking have caused serious environmental pollution worldwide. Phytoremediation is an efficient technology in treating hazardous wastes from the environment. However, the phytoremediation efficiency of thiocyanate is very low due to the fact that plants lack thiocyanate degradation enzymes. In this study, the thiocyanate hydrolase module was assembled correctly in rice seedlings and showed thiocyanate hydrolase activity. Rice seedlings engineered to express thiocyanate degrading activity were able to completely remove thiocyanate from coking wastewater. Our findings suggest that transforming the thiocyanate hydrolase module into plants is an efficient strategy for rapid phytoremediation of thiocyanate in the environment. Moreover, the rice seedlings expressing apoplastic or cytoplasmic targeted thiocyanate hydrolase module were constructed to compare the phytoremediation efficiency of secretory/intracellular recombinant thiocyanate hydrolase. The most obvious finding from this study is that the apoplastic expression system is more efficient than the cytoplasm expression system in the phytoremediation of thiocyanate. At last, this research also shows that the secreted thiocyanate hydrolase from engineered rice plants does not influence rhizosphere bacterial community composition.

Integrative comparative analyses of metabolite and transcript profiles uncovers complex regulatory network in tomato (Solanum lycopersicum L.) fruit undergoing chilling injury.

Tomato fruit are especially susceptible to chilling injury (CI) when continuously exposed to temperatures below 12 °C. In this study, integrative comparative analyses of transcriptomics and metabolomics data were performed to uncover the regulatory network in CI tomato fruit. Metabolite profiling analysis found that 7 amino acids, 27 organic acids, 16 of sugars and 22 other compounds had a significantly different content while transcriptomics data showed 1735 differentially expressed genes (DEGs) were down-regulated and 1369 were up-regulated in cold-stored fruit. We found that the contents of citrate, cis-aconitate and succinate were increased, which were consistent with the expression of ATP-citrate synthase (ACS) and isocitrate dehydrogenase (IDH) genes in cold-treated tomato fruit. Cold stress promotes the expression of ACS and IDH which may increase the synthesis of citrate, cis-aconitate and succinate. Alanine and leucine had increased contents, which may result from alanine aminotransferase (ALT) and branched-chain amino acid aminotransferase (BcAT)'s high expression levels, respectively. Overall the transcriptomics and metabolomics data in our study explain the molecular mechanisms of the chilling injury and expands our understanding of the complex regulatory mechanisms of a metabolic network in response to chilling injury in tomato fruit.