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OBSERVED increases in concentrations of chlorine in the stratosphere1-7 have been widely implicated in the depletion of lower-stratospheric ozone over the past two decades8-14. The present concentration of stratospheric chlorine is more than five times that expected from known natural 'background' emissions from the oceans and biomass burning15-18, and the balance has been estimated to be dominantly anthropogenic in origin, primarily due to the breakdown products of chlorofluorocarbons (CFCs)19,20. But despite the wealth of scientific data linking chlorofluorocarbon emissions to the observed chlorine increases, the political sensitivity of the ozone-depletion issue has generated a re-examination of the evidence21,22. Here we report a four-year global time series of satellite observations of hydrogen chloride (HCl) and hydrogen fluoride (HF) in the stratosphere, which shows conclusively that chlorofluorocarbon releases - rather than other anthropogenic or natural emissions - are responsible for the recent global increases in stratospheric chlorine concentrations. Moreover, all but a few per cent of observed stratospheric chlorine amounts can be accounted for by known natural and anthropogenic tropospheric emissions. Altogether, these results implicate the chlorofluorocarbon s beyond reasonable doubt as dominating ozone depletion in the lower stratosphere.

Measurements of nitric oxide mixing ratios have been made by the Halogen Occultation Experiment on the Upper Atmosphere Research Satellite over an altitude range extending from 15 to 130 km on every spacecraft sunrise and sunset event with the exception of about 8% downtime. Selected NO profiles from the first few months of observations were examined with emphasis on the relation between geomagnetic disturbances and enhanced NO in the lower thermosphere. During a large geomagnetic storm on November 8–9, 1991, HALOE obtained 15 NO sunrise profiles along the ∼50°N latitude circle. A factor of 3 increase in NO mixing ratio above ∼115 km at this latitude and a one to two day decay time were observed. The measured NO longitude/altitude cross section on this day shows a longitudinal asymmetry in the NO distribution with a maximum near the geomagnetic pole. From approximately one month's data, a latitude/altitude cross section of zonal mean NO mixing ratio was calculated. An example of such cross sections demonstrates a strong positive correlation between geomagnetic activity and thermospheric NO globally. This auroral forcing has a larger effect on increasing NO at high latitude than at low latitude. Copyright 1993 by the American Geophysical Union.

The Tropospheric Emission Spectrometer (TES) is a high-resolution spaceborne sensor that is capable of observing tropospheric species. In order to exploit fully TES's potential for tropospheric constituent retrievals, an accurate and fast operational forward model was developed for TES. The forward model is an important component of the TES retrieval model, the Earth Limb and Nadir Operational Retrieval (ELANOR), as it governs the accuracy and speed of the calculations for the retrievals. In order to achieve the necessary accuracy and computational efficiency, TES adopted the strategy of utilizing precalculated absorption coefficients generated by the line-by-line calculations provided by line-by-line radiation transfer modeling. The decision to perform the radiative transfer with the highest monochromatic accuracy attainable, rather than with an accelerated scheme that has the potential to add algorithmic forward model error, has proven to be very successful for TES retrievals. A detailed description of the TES forward model and Jacobians is described. A preliminary TES observation is provided as an example to demonstrate that the TES forward model calculations represent TES observations. Also presented is a validation example, which is part of the extensive forward model validation effort. Index Terms--Earth Limb and Nadir Operational Retrieval (ELANOR), forward model, Jacobians, line-by-line radiation transfer modeling (LBLRTM), radiative transfer (RT), TES, Tropospheric Emission Spectrometer (TES).

The Tropospheric Emission Spectromter (TES) on the Earth Observing System (EOS) Aura satellite measures the infrared radiance emitted by the Earth's surface and atmosphere using Fourier transform spectrometry. The measured interferograms are converted into geolocated, calibrated radiance spectra by the L1 (Level 1) processing, and are the inputs to L2 (Level 2) retrievals of atmospheric parameters, such as vertical profiles of trace gas abundance. We describe the algorithmic components of TES Level 1 processing, giving examples of the intermediate results and diagnostics that are necessary for creating TES L1 products. An assessment of noise-equivalent spectral radiance levels and current systematic errors is provided. As an initial validation of our spectral radiances, TES data are compared to the Atmospheric Infrared Sounder (AIRS) (on EOS Aqua), after accounting for spectral resolution differences by applying the AIRS spectral response function to the TIES spectra. For the TES L1 nadir data products currently available, the agreement with AIRS is 1 K or better. Index Terms--Aura, Earth Observing System (EOS), Fourier Transform Spectrometry (FTS), infrared remote sensing, radiometric calibration, Tropospheric Emission Spectrometer (TES).

C4 plants exhibit significantly higher photosynthetic, water and nutrient use efficiency compared with C3 plants. Kranz anatomy is associated with many C4 plants in which bundle sheath cells surround the veins and are themselves surrounded by mesophyll cells. This specialized Kranz anatomy is elucidated as an important contributor to C4 photosynthetic activities in C4 plant. Characterizing the molecular basis of Kranz structure formation has become a key objective for studies of C4 photosynthesis. However, severe mutants that specifically disrupt Kranz anatomy have not been identified. In this study, we detected 549 stable ethyl methane sulfonate-induced foxtail millet (cultivar Yugu1) mutants related to leaf development and photosynthesis among 2,709 mutants screened (M3/M4 generation). The identified mutants included 52 that had abnormal leaf veins (with abnormal starch accumulation based on iodine staining). Each of the 52 mutants was characterized through an analysis of leaf morphology, and through microscopic observations of leaf tissue sections embedded in resin and paraffin. In total, 14 mutants were identified with abnormal Kranz structures exemplified by small bundle sheath cell size. Additional phenotypes of the mutants included poorly differentiated mesophyll and bundle sheath cells, increased vein density and the absence of chloroplasts in the bundle sheath cells. Kranz structure mutations were accompanied by varying leaf thickness, implying these mutations induced complex effects. We identified mutations related to Kranz structure development in this trial, which may be useful for the mapping and cloning of genes responsible for mediating Kranz structure development. [ABSTRACT FROM AUTHOR]

Deoxycytidine monophosphate deaminase (DCD) is a key enzyme in the de novo dTTP biosynthesis pathway. Previous studies have indicated that DCD plays key roles in the maintenance of the balance of dNTP pools, cell cycle progression, and plant development. However, few studies have elucidated the functions of the DCD gene in Panicoideae plants. Setaria has been proposed as an ideal model of Panicoideae grasses, especially for C4 photosynthesis research. Here, a Setaria italica stripe leaf mutant (sistl2) was isolated from EMS-induced lines of “Yugu1,” the wild-type parent. The sistl2 mutant exhibited semi-dwarf, striped leaves, abnormal chloroplast ultrastructure, and delayed cell cycle progression compared with Yugu1. High-throughput sequencing and map-based cloning identified the causal gene SiSTL2 , which encodes a DCD protein. The occurrence of a single-base G to A substitution in the fifth intron introduced alternative splicing, which led to the early termination of translation. Further physiological and transcriptomic investigation indicated that SiSTL2 plays an essential role in the regulation of chloroplast biogenesis, cell cycle, and DNA replication, which suggested that the gene has conserved functions in both foxtail millet and rice. Remarkably, in contrast to DCD mutants in C3 rice, sistl2 showed a significant reduction in leaf cell size and affected C4 photosynthetic capacity in foxtail millet. qPCR showed that SiSTL2 had a similar expression pattern to typical C4 genes in response to a low CO2 environment. Moreover, the loss of function of SiSTL2 resulted in a reduction of leaf 13C content and the enrichment of DEGs in photosynthetic carbon fixation. Our research provides in-depth knowledge of the role of DCD in the C4 photosynthesis model S. italica and proposed new directions for further study of the function of DCD. [ABSTRACT FROM AUTHOR]

C 4 plants exhibit significantly higher photosynthetic, water and nutrient use efficiency compared with C 3 plants. Kranz anatomy is associated with many C 4 plants in which bundle sheath cells surround the veins and are themselves surrounded by mesophyll cells. This specialized Kranz anatomy is elucidated as an important contributor to C 4 photosynthetic activities in C 4 plant. Characterizing the molecular basis of Kranz structure formation has become a key objective for studies of C 4 photosynthesis. However, severe mutants that specifically disrupt Kranz anatomy have not been identified. In this study, we detected 549 stable ethyl methane sulfonate-induced foxtail millet (cultivar Yugu1) mutants related to leaf development and photosynthesis among 2,709 mutants screened (M 3 /M 4 generation). The identified mutants included 52 that had abnormal leaf veins (with abnormal starch accumulation based on iodine staining). Each of the 52 mutants was characterized through an analysis of leaf morphology, and through microscopic observations of leaf tissue sections embedded in resin and paraffin. In total, 14 mutants were identified with abnormal Kranz structures exemplified by small bundle sheath cell size. Additional phenotypes of the mutants included poorly differentiated mesophyll and bundle sheath cells, increased vein density and the absence of chloroplasts in the bundle sheath cells. Kranz structure mutations were accompanied by varying leaf thickness, implying these mutations induced complex effects. We identified mutations related to Kranz structure development in this trial, which may be useful for the mapping and cloning of genes responsible for mediating Kranz structure development.

Deoxycytidine monophosphate deaminase (DCD) is a key enzyme in the de novo dTTP biosynthesis pathway. Previous studies have indicated that DCD plays key roles in the maintenance of the balance of dNTP pools, cell cycle progression, and plant development. However, few studies have elucidated the functions of the DCD gene in Panicoideae plants. Setaria has been proposed as an ideal model of Panicoideae grasses, especially for C 4 photosynthesis research. Here, a Setaria italica stripe leaf mutant ( sistl2 ) was isolated from EMS-induced lines of "Yugu1," the wild-type parent. The sistl2 mutant exhibited semi-dwarf, striped leaves, abnormal chloroplast ultrastructure, and delayed cell cycle progression compared with Yugu1. High-throughput sequencing and map-based cloning identified the causal gene SiSTL2 , which encodes a DCD protein. The occurrence of a single-base G to A substitution in the fifth intron introduced alternative splicing, which led to the early termination of translation. Further physiological and transcriptomic investigation indicated that SiSTL2 plays an essential role in the regulation of chloroplast biogenesis, cell cycle, and DNA replication, which suggested that the gene has conserved functions in both foxtail millet and rice. Remarkably, in contrast to DCD mutants in C 3 rice, sistl2 showed a significant reduction in leaf cell size and affected C 4 photosynthetic capacity in foxtail millet. qPCR showed that SiSTL2 had a similar expression pattern to typical C 4 genes in response to a low CO 2 environment. Moreover, the loss of function of SiSTL2 resulted in a reduction of leaf 13 C content and the enrichment of DEGs in photosynthetic carbon fixation. Our research provides in-depth knowledge of the role of DCD in the C 4 photosynthesis model S. italica and proposed new directions for further study of the function of DCD.