Identification and characterization of a novel sativene synthase from Fischerella thermalis.

Sesquiterpene synthases (TPS) determine the structural diversity of terpenoids, which are species specific. In this study, we report a TPS from Fischerella thermalis (named as FtTPS), recombinantly expressed as a soluble protein in Escherichia coli BL21(DE3) strain. The FtTPS protein could catalyze the conversion of farnesyl pyrophosphate (FPP) to sativene, a kind of tricyclic sesquiterpene. The optimal pH and temperature of FtTPS were 7.5 and 30 °C, respectively. The KM and Vmax values of FtTPS for FPP were 1.846 µM and 0.372 µM/min, respectively. By constructing an engineered E. coli strain carrying the FtTPS and the heterologous mevalonate (MVA) pathway genes, sativene could be detected and its yield reached 24 mg/L after 96 h cultivation. The highest yield of sativene was obtained when E.coli BL21 Star was used as the host with SBMSN medium. These results exhibited the biosynthesis of sativene for the first time.

Effect of different vegetation restoration on soil organic carbon dynamics and fractions in the Rainy Zone of Western China.

Vegetation restoration on purple soil (Eutric Leptic Regosols) slopes aiming at reducing soil erosion in the Rainy Zone of Western China has significantly altered soil organic carbon (SOC) storage and distribution. A better understanding of the effects of different vegetation restoration types on SOC dynamics and fractions is critical in devising better policy to protect or enhance SOC stocks to improve soil quality and ecosystem function. In the present study, total, labile, and non-labile organic carbon (TOC, LC, and NLC), and carbon management index (CMI) of Cryptomeria fortunei (CF), mixed C. fortunei and Betula luminifera (MF), Neosinocalamus affinis (NA), and Camellia sinensis (CS) were compared with those of Zea mays field (ZM) on purple soil slopes in the Rainy Zone of Western China in order to develop more effective ways to implement vegetation restoration in the future. Different vegetation restoration types (CF, MF, NA and CS) increased TOC stock by 47.79%-118.31% and NLC stock by 56.61%-129.52% in the 0-50 cm soil layer compared with that of ZM. The direction and magnitude of changes in LC stock and CMI, however, depended strongly on the vegetation restoration type. Compared with ZM, CF had the largest increase of LC stock and CMI, whereas NA had the largest decrease of LC stock and CMI in the 0-50 cm soil layer. The LC:TOC ratio in four reforested species all declined significantly compared with that of ZM (p < 0.01), indicating decreased SOC activity after afforestation. The vegetation type and soil depth together explained more than 90% of the changes of TOC and its fractions in the plantations on purple soil slopes. Our study demonstrates that transforming the ZM into the CS is optimal to achieve the sustainable development goal, whereas transforming the ZM into the NA reduces the SOC activity and availability.