Encroachment of woody plants into grasslands is a global phenomenon that has substantial impacts on pastoral productivity and ecosystem services. Over the past half century, pastoralists and land management agencies have explored various options to control woody plants in order to improve ecosystem services in shrub‐encroached grasslands. We examined the effectiveness of controlling the encroachment of the shrub Caragana microphylla into grassland in Inner Mongolia, China. We cut and removed all of the aboveground biomass from 450 shrubs, predicting that the effectiveness of this technique to control shrubs would depend on shrub morphology. Specifically, we expected that larger shrubs with more biomass would be more difficult to kill by cutting than smaller shrubs. A year after treatment, we found that cutting killed only 11% of the 450 treated shrubs, and of these, three‐quarters of the locations that they occupied reverted to grasses and one‐quarter to bare soil. Shrubs that survived the cutting treatment produced more stems and leaf biomass, and therefore had a greater leaf to stem ratio. Shrubs that died after cutting had a lower crown area and basal area, and less stem biomass than shrubs that resprouted within 12 months of cutting. There were no effects of shrub height on the fate of treated shrubs. Cutting had no effect on understory plant cover or richness, but reproductive plants were taller under shrubs that were not cut. Overall, our study showed that removing aboveground shrub biomass by cutting is an ineffective technique for “restoring” the original grassland community unless shrubs are very small. Strategic targeting of small shrubs would be a more effective technique for controlling the spread of C. microphylla in the long term. 相似文献
Science China Life Sciences - Human alpha-2-macroglobulin is a well-known inhibitor of a broad spectrum of proteases and plays important roles in immunity, inflammation, and infections. Here, we... 相似文献
Heavy metals, that is Cu(II), are harmful to the environment. There is an increasing demand to develop inexpensive detection methods for heavy metals. Here, we developed a yeast biosensor with reduced-noise and improved signal output for potential on-site copper ion detection. The copper-sensing circuit was achieved by employing a secondary genetic layer to control the galactose-inducible (GAL) system in Saccharomyces cerevisiae. The reciprocal control of the Gal4 activator and Gal80 repressor under copper-responsive promoters resulted in a low-noise and sensitive yeast biosensor for copper ion detection. Furthermore, we developed a betaxanthin-based colorimetric assay, as well as 2-phenylethanol and styrene-based olfactory outputs for the copper ion detection. Notably, our engineered yeast sensor confers a narrow range switch-like behaviour, which can give a ‘yes/no’ response when coupled with a betaxanthin-based visual phenotype. Taken together, we envision that the design principle established here might be applicable to develop other sensing systems for various chemical detections. 相似文献
Plant-parasitic nematodes need to deliver effectors that suppress host immunity for successful parasitism. We have characterized a novel isochorismatase effector from the root-knot nematode Meloidogyne incognita, named Mi-ISC-1. The Mi-isc-1 gene is expressed in the subventral oesophageal glands and is up-regulated in parasitic-stage juveniles. Tobacco rattle virus-induced gene silencing targeting Mi-isc-1 attenuated M. incognita parasitism. Enzyme activity assays confirmed that Mi-ISC-1 can catalyse hydrolysis of isochorismate into 2,3-dihydro-2,3-dihydroxybenzoate in vitro. Although Mi-ISC-1 lacks a classical signal peptide for secretion at its N-terminus, a yeast invertase secretion assay showed that this protein can be secreted from eukaryotic cells. However, the subcellular localization and plasmolysis assay revealed that the unconventional secretory signal present on the Mi-ISC-1 is not recognized by the plant secretory pathway and that the effector was localized within the cytoplasm of plant cells, but not apoplast, when transiently expressed in Nicotiana benthamiana leaves by agroinfiltration. Ectopic expression of Mi-ISC-1 in N. benthamiana reduced expression of the PR1 gene and levels of salicylic acid (SA), and promoted infection by Phytophthora capsici. The cytoplasmic localization of Mi-ISC-1 is required for its function. Moreover, Mi-ISC-1 suppresses the production of SA following the reconstitution of the de novo SA biosynthesis via the isochorismate pathway in the cytoplasm of N. benthamiana leaves. These results demonstrate that M. incognita deploys a functional isochorismatase that suppresses SA-mediated plant defences by disrupting the isochorismate synthase pathway for SA biosynthesis to promote parasitism. 相似文献
As the services provided by cloud vendors are providing better performance, achieving auto-scaling, load-balancing, and optimized performance along with low infrastructure maintenance, more and more companies migrate their services to the cloud. Since the cloud workload is dynamic and complex, scheduling the jobs submitted by users in an effective way is proving to be a challenging task. Although a lot of advanced job scheduling approaches have been proposed in the past years, almost all of them are designed to handle batch jobs rather than real-time workloads, such as that user requests are submitted at any time with any amount of numbers. In this work, we have proposed a Deep Reinforcement Learning (DRL) based job scheduler that dispatches the jobs in real time to tackle this problem. Specifically, we focus on scheduling user requests in such a way as to provide the quality of service (QoS) to the end-user along with a significant reduction of the cost spent on the execution of jobs on the virtual instances. We have implemented our method by Deep Q-learning Network (DQN) model, and our experimental results demonstrate that our approach can significantly outperform the commonly used real-time scheduling algorithms.