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Micro-RNAs are cellular components regulating gene expression at the post-transcription level. In the present study, artificial micro-RNAs were used to decrease the transcript level of two genes, AtExpA8 (encoding an expansin) and AHL25 (encoding an AT-hook motif nuclear localized protein) in Arabidopsis thaliana. The backbone of the Arabidopsis endogenous MIR319a micro-RNA was used in a site-directed mutagenesis approach for the generation of artificial micro-RNAs targeting two genes. The recombinant cassettes were expressed under the control of the CaMV 35S promoter in individual A. thaliana plants. Transgenic lines of the third generation were tested by isolating total RNA and by subsequent cDNA synthesis using oligo-dT18 primers and mRNAs as templates. The expression of the two target genes was checked through quantitative realtime polymerase chain reaction to confirm reduced transcript levels for AtExpA8 and AHL25. Downregulation of AtExpA8 resulted in the formation of short hypocotyls compared with those of the wild-type control in response to low pH and high salt concentration. This technology could be used to prevent the expression of exogenous and invading genes posing a threat to the normal cellular physiology of the host plant.
River ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of which depends strongly on microbial activity. Variation in and controls of processing rates, however, are poorly characterized at the global scale. In response, we used a peer-sourced research network and a highly standardized carbon processing assay to conduct a global-scale field experiment in greater than 1000 river and riparian sites. We found that Earth’s biomes have distinct carbon processing signatures. Slow processing is evident across latitudes, whereas rapid rates are restricted to lower latitudes. Both the mean rate and variability decline with latitude, suggesting temperature constraints toward the poles and greater roles for other environmental drivers (e.g., nutrient loading) toward the equator. These results and data set the stage for unprecedented “next-generation biomonitoring” by establishing baselines to help quantify environmental impacts to the functioning of ecosystems at a global scale.