Earth system models (ESMs) use photosynthetic capacity, indexed by the maximum Rubisco carboxylation rate (Vcmax), to simulate carbon assimilation and typically rely on empirical estimates, including ...an assumed dependence on leaf nitrogen determined from soil fertility. In contrast, new theory, based on biochemical coordination and co‐optimization of carboxylation and water costs for photosynthesis, suggests that optimal Vcmax can be predicted from climate alone, irrespective of soil fertility. Here, we develop this theory and find it captures 64% of observed variability in a global, field‐measured Vcmax dataset for C3 plants. Soil fertility indices explained substantially less variation (32%). These results indicate that environmentally regulated biophysical constraints and light availability are the first‐order drivers of global photosynthetic capacity. Through acclimation and adaptation, plants efficiently utilize resources at the leaf level, thus maximizing potential resource use for growth and reproduction. Our theory offers a robust strategy for dynamically predicting photosynthetic capacity in ESMs.
Bioluminescence is a natural light source based on luciferase catalysis of its substrate luciferin. We performed directed evolution on firefly luciferase using a red-shifted and highly deliverable ...luciferin analog to establish AkaBLI, an all-engineered bioluminescence in vivo imaging system. AkaBLI produced emissions in vivo that were brighter by a factor of 100 to 1000 than conventional systems, allowing noninvasive visualization of single cells deep inside freely moving animals. Single tumorigenic cells trapped in the mouse lung vasculature could be visualized. In the mouse brain, genetic labeling with neural activity sensors allowed tracking of small clusters of hippocampal neurons activated by novel environments. In a marmoset, we recorded video-rate bioluminescence from neurons in the striatum, a deep brain area, for more than 1 year. AkaBLI is therefore a bioengineered light source to spur unprecedented scientific, medical, and industrial applications.
We examined whether variations in photosynthetic capacity are linked to variations in the environment and/or associated leaf traits for tropical moist forests (TMFs) in the Andes/western Amazon ...regions of Peru.
We compared photosynthetic capacity (maximal rate of carboxylation of Rubisco (V
cmax), and the maximum rate of electron transport (J
max)), leaf mass, nitrogen (N) and phosphorus (P) per unit leaf area (M
a, Na and Pa, respectively), and chlorophyll from 210 species at 18 field sites along a 3300-m elevation gradient. Western blots were used to quantify the abundance of the CO2-fixing enzyme Rubisco.
Area- and N-based rates of photosynthetic capacity at 25°C were higher in upland than lowland TMFs, underpinned by greater investment of N in photosynthesis in high-elevation trees. Soil P and leaf Pa were key explanatory factors for models of area-based V
cmax and J
max but did not account for variations in photosynthetic N-use efficiency. At any given Na and Pa, the fraction of N allocated to photosynthesis was higher in upland than lowland species. For a small subset of lowland TMF trees examined, a substantial fraction of Rubisco was inactive.
These results highlight the importance of soil- and leaf-P in defining the photosynthetic capacity of TMFs, with variations in N allocation and Rubisco activation state further influencing photosynthetic rates and N-use efficiency of these critically important forests.
Dysfunctional mitochondria accumulate in many human diseases. Accordingly, mitophagy, which removes these mitochondria through lysosomal degradation, is attracting broad attention. Due to ...uncertainties in the operational principles of conventional mitophagy probes, however, the specificity and quantitativeness of their readouts are disputable. Thorough investigation of the behaviors and fates of fluorescent proteins inside and outside lysosomes enabled us to develop an indicator for mitophagy, mito-SRAI. Through strict control of its mitochondrial targeting, we were able to monitor mitophagy in fixed biological samples more reproducibly than before. Large-scale image-based high-throughput screening led to the discovery of a hit compound that induces selective mitophagy of damaged mitochondria. In a mouse model of Parkinsons disease, we found that dopaminergic neurons selectively failed to execute mitophagy that promoted their survival within lesions. These results show that mito-SRAI is an essential tool for quantitative studies of mitochondrial quality control.
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•mito-SRAI provides reliable mitophagy readouts under both live and fixed conditions•mito-SRAI uses a fluorescent protein that is resistant to lysosomal environments•High-throughput screening led to the discovery of mitophagy-inducing compounds•Evidence was given for loss of nigral dopaminergic neurons due to mitophagy failure
Through investigation of the behaviors and fates of fluorescent proteins inside and outside of lysosomes, Katayama et al. developed a signal-retaining autophagy indicator, which they localize to mitochondria (mito-SRAI) to quantitatively measure mitophagy. They apply their new tool in a high-throughput in vitro screen for chemical inducers of mitophagy and in a mouse model of Parkinsons disease.
Changes in precipitation in the Amazon Basin resulting from regional deforestation, global warming, and El Niño events may affect emissions of carbon dioxide (CO₂), methane (CH₄), nitrous oxide ...(N₂O), and nitric oxide (NO) from soils. Changes in soil emissions of radiatively important gases could have feedback implications for regional and global climate. Here, we report the final results of a 5-year, large-scale (1 ha) throughfall exclusion experiment, followed by 1 year of recovery with natural throughfall, conducted in a mature evergreen forest near Santarém, Brazil. The exclusion manipulation lowered annual N₂O emissions in four out of five treatment years (a natural drought year being the exception), and then recovered during the first year after the drought treatment stopped. Similarly, consumption of atmospheric CH₄ increased under drought treatment, except during a natural drought year, and it also recovered to pretreatment values during the first year that natural throughfall was permitted back on the plot. No treatment effect was detected for NO emissions during the first 3 treatment years, but NO emissions increased in the fourth year under the extremely dry conditions of the exclusion plot during a natural drought. Surprisingly, there was no treatment effect on soil CO₂ efflux in any year. The drought treatment provoked significant tree mortality and reduced the allocation of C to stems, but allocation of C to foliage and roots were less affected. Taken together, these results suggest that the dominant effect of throughfall exclusion on soil processes during this 6-year period was on soil aeration conditions that transiently affected CH₄, N₂O, and NO production and consumption.
Simulations of photosynthesis by terrestrial biosphere models typically need a specification of the maximum carboxylation rate (V
cmax). Estimating this parameter using A–C
i curves (net ...photosynthesis, A, vs intercellular CO2 concentration, C
i) is laborious, which limits availability of V
cmax data. However, many multispecies field datasets include net photosynthetic rate at saturating irradiance and at ambient atmospheric CO2 concentration (A
sat) measurements, from which V
cmax can be extracted using a ‘one-point method’.
We used a global dataset of A–C
i curves (564 species from 46 field sites, covering a range of plant functional types) to test the validity of an alternative approach to estimate V
cmax from A
sat via this ‘one-point method’.
If leaf respiration during the day (R
day) is known exactly, V
cmax can be estimated with an r
2 value of 0.98 and a root-mean-squared error (RMSE) of 8.19 μmolm−2 s−1. However, R
day typically must be estimated. Estimating R
day as 1.5% of V
cmax, we found that V
cmax could be estimated with an r
2 of 0.95 and an RMSE of 17.1 μmolm−2 s−1.
The one-point method provides a robust means to expand current databases of fieldmeasured V
cmax, giving new potential to improve vegetation models and quantify the environmental drivers of V
cmax variation.
Abstract
Type 2 diabetes mellitus (T2DM) has long been considered a risk factor for Alzheimer’s disease (AD). However, the molecular links between T2DM and AD remain obscure. Here, we reported that ...serum-/glucocorticoid-regulated kinase 1 (SGK1) is activated by administering a chronic high-fat diet (HFD), which increases the risk of T2DM, and thus promotes Tau pathology via the phosphorylation of tau at Ser214 and the activation of a key tau kinase, namely, GSK-3ß, forming SGK1-GSK-3ß-tau complex. SGK1 was activated under conditions of elevated glucocorticoid and hyperglycemia associated with HFD, but not of fatty acid–mediated insulin resistance. Elevated expression of SGK1 in the mouse hippocampus led to neurodegeneration and impairments in learning and memory. Upregulation and activation of SGK1, SGK1-GSK-3ß-tau complex were also observed in the hippocampi of AD cases. Our results suggest that SGK1 is a key modifier of tau pathology in AD, linking AD to corticosteroid effects and T2DM.
Isoprene is emitted from many terrestrial plants at high rates, accounting for an estimated 1/3 of annual global volatile organic compound emissions from all anthropogenic and biogenic sources ...combined. Through rapid photooxidation reactions in the atmosphere, isoprene is converted to a variety of oxidized hydrocarbons, providing higher order reactants for the production of organic nitrates and tropospheric ozone, reducing the availability of oxidants for the breakdown of radiatively active trace gases such as methane, and potentially producing hygroscopic particles that act as effective cloud condensation nuclei. However, the functional basis for plant production of isoprene remains elusive. It has been hypothesized that in the cell isoprene mitigates oxidative damage during the stress‐induced accumulation of reactive oxygen species (ROS), but the products of isoprene‐ROS reactions in plants have not been detected. Using pyruvate‐2‐13C leaf and branch feeding and individual branch and whole mesocosm flux studies, we present evidence that isoprene (i) is oxidized to methyl vinyl ketone and methacrolein (iox) in leaves and that iox/i emission ratios increase with temperature, possibly due to an increase in ROS production under high temperature and light stress. In a primary rainforest in Amazonia, we inferred significant in plant isoprene oxidation (despite the strong masking effect of simultaneous atmospheric oxidation), from its influence on the vertical distribution of iox uptake fluxes, which were shifted to low isoprene emitting regions of the canopy. These observations suggest that carbon investment in isoprene production is larger than that inferred from emissions alone and that models of tropospheric chemistry and biota–chemistry–climate interactions should incorporate isoprene oxidation within both the biosphere and the atmosphere with potential implications for better understanding both the oxidizing power of the troposphere and forest response to climate change.
Phosphorus (P) is generally considered the most common limiting nutrient for productivity of mature tropical lowland forests growing on highly weathered soils. It is often assumed that P limitation ...also applies to young tropical forests, but nitrogen (N) losses during land-use change may alter the stoichiometric balance of nutrient cycling processes. In the Amazon basin, about 16% of the original forest area has been cleared, and about 30-50% of cleared land is estimated now to be in some stage of secondary forest succession following agricultural abandonment. Here we use forest age chronosequences to demonstrate that young successional forests growing after agricultural abandonment on highly weathered lowland tropical soils exhibit conservative N-cycling properties much like those of N-limited forests on younger soils in temperate latitudes. As secondary succession progresses, N-cycling properties recover and the dominance of a conservative P cycle typical of mature lowland tropical forests re-emerges. These successional shifts in N:P cycling ratios with forest age provide a mechanistic explanation for initially lower and then gradually increasing soil emissions of the greenhouse gas nitrous oxide (N2O). The patterns of N and P cycling during secondary forest succession, demonstrated here over decadal timescales, are similar to N- and P-cycling patterns during primary succession as soils age over thousands and millions of years, thus revealing that N availability in terrestrial ecosystems is ephemeral and can be disrupted by either natural or anthropogenic disturbances at several timescales.
The claustrum coordinates the activities of individual cortical areas through abundant reciprocal connections with the cerebral cortex. Although these excitatory connections have been extensively ...investigated in three subregions of the claustrum—core region and dorsal and ventral shell regions—the contribution of GABAergic neurons to the circuitry in each subregion remains unclear. Here, we examined the distribution of GABAergic neurons and their dendritic and axonal arborizations in each subregion. Combining in situ hybridization with immunofluorescence histochemistry showed that approximately 10% of neuronal nuclei-positive cells expressed glutamic acid decarboxylase 67 mRNA across the claustral subregions. Approximately 20%, 30%, and 10% of GABAergic neurons were immunoreactive for parvalbumin (PV), somatostatin (SOM), and vasoactive intestinal polypeptide, respectively, in each subregion, and these neurochemical markers showed little overlap with each other. We then reconstructed PV and SOM neurons labeled with adeno-associated virus vectors. The dendrites and axons of PV and SOM neurons were preferentially localized to their respective subregions where their cell bodies were located. Furthermore, the axons were preferentially extended in a rostrocaudal direction, whereas the dendrites were relatively isotropic. The present findings suggest that claustral PV and SOM neurons might execute information processing separately within the core and shell regions.
•The distribution of GABAergic neurons is examined in claustral subregions.•Nearly 10% of claustral neurons are GABAergic in each claustral subregion.•PV-, SOM-, and VIP-positive neurons comprise 20%, 30%, and 10% of GABAergic neurons.•PV and SOM neurons preferentially extend the axons along a rostrocaudal axis.•PV and SOM neurons localize the neurites within either the core or shell subregion.
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