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Internode_lengths_AveragePerGroup_Stage5.csv = averaged internode lengths for each treatment groups at stage 5  (plastochron 9). Data represented in Appendix S2. Internode_lengths_Stage5.csv = data of all internodes lengths per individual plant at stage 5 (plastochron 9). Data represented in Appendix S2. InternodeLengths_allStages.csv = internode lengths through 5 stages (0-9 plastochon). Data represented in Appendix S1. Associated scripts: https://github.com/angelique-acevedo/Common-Bean-Analysis 

Synaptically released zinc is a neuronal signaling system that arises from the actions of the presynaptic vesicular zinc transporter protein zinc transporter 3 (ZnT3). Mechanisms that regulate the actions of zinc at synapses are of great importance for many aspects of synaptic signaling in the brain. Here, we identify the astrocytic zinc transporter protein ZIP12 as a candidate mechanism that contributes to zinc clearance at cortical synapses. We identify small-molecule compounds that antagonize the function of ZIP12 in heterologous expression systems, and we use one of these compounds, ZIP12 modulator 8, to increase the concentration of ZnT3-dependent zinc at synapses in the brain of male and female mice to inhibit the activity of neuronal AMPA and NMDA glutamate receptors. These results identify a cellular mechanism and provide a pharmacological toolbox to target the molecular machinery that supports the actions of synaptic zinc in the brain. 

Abstract BackgroundLike all plant cells, the guard cells of stomatal complexes are encased in cell walls that are composed of diverse, interacting networks of polysaccharide polymers. The properties of these cell walls underpin the dynamic deformations that occur in guard cells as they expand and contract to drive the opening and closing of the stomatal pore, the regulation of which is crucial for photosynthesis and water transport in plants. ScopeOur understanding of how cell wall mechanics are influenced by the nanoscale assembly of cell wall polymers in guard cell walls, how this architecture changes over stomatal development, maturation and ageing and how the cell walls of stomatal guard cells might be tuned to optimize stomatal responses to dynamic environmental stimuli is still in its infancy. ConclusionIn this review, we discuss advances in our ability to probe experimentally and to model the structure and dynamics of guard cell walls quantitatively across a range of plant species, highlighting new ideas and exciting opportunities for further research into these actively moving plant cells. 

Abstract Following a nuclear war, destruction would extend well beyond the blast zones due to the onset of a nuclear winter that can devastate the biosphere, including agriculture. Understanding the damage magnitude and preparing for the folly of its occurrence are critical given current geopolitical tensions. We developed and applied a framework to simulate global crop production under a nuclear winter using the Cycles agroecosystem model, incorporating ultraviolet (UV)-B radiation effects on plant growth and adaptive selection of crop maturity types (shorter cycle the lower the temperature). Using maize (Zea maizeL.) as a sentinel crop, we found that annual maize production could decline from 7% after a small-scale regional nuclear war with 5 Tg soot injection, to 80% after a global nuclear war with 150 Tg soot injection, with recovery taking from 7 to 12 years. UV-B damage would peak 6–8 years post-war and can further decrease annual maize production by 7%. Over the recovery period, adaptive selection of maize maturity types to track changing temperatures could increase production by 10% compared to a no-adaptation strategy. Seed availability may become a critical adaptation bottleneck; this and prior studies might underestimate food production declines. We propose that adaptation must include the development of Agricultural Resilience Kits consisting of region- and climate-specific seed and technology packages designed to buffer against uncertainty while supply chains recover. These kits would be congenial with the transient conditions during the recovery period, and would also be applicable to other catastrophes affecting food production. 

SUMMARY Stomata are pores at the leaf surface that enable gas exchange and transpiration. The signaling pathways that regulate the differentiation of stomatal guard cells and the mechanisms of stomatal pore formation have been characterized inArabidopsis thaliana. However, the process by which stomatal complexes develop after pore formation into fully mature complexes is poorly understood. We tracked the morphogenesis of young stomatal complexes over time to establish characteristic geometric milestones along the path of stomatal maturation. Using 3D‐nanoindentation coupled with finite element modeling of young and mature stomata, we found that despite having thicker cell walls than young guard cells, mature guard cells are more energy efficient with respect to stomatal opening, potentially attributable to the increased mechanical anisotropy of their cell walls and smaller changes in turgor pressure between the closed and open states. Comparing geometric changes in young and mature guard cells of wild‐type and cellulose‐deficient plants revealed that although cellulose is required for normal stomatal maturation, mechanical anisotropy appears to be achieved by the collective influence of cellulose and additional wall components. Together, these data elucidate the dynamic geometric and biomechanical mechanisms underlying the development process of stomatal maturation. 

Efficient cellulose degradation by cellulase enzymes is crucial for using lignocellulosic biomass in bioenergy production. Single-molecule microscopy showed that xylan hinders the efficiency of cellulase by inhibiting its binding to cellulose and impeding the processivity of bound enzyme molecules. 

Degrading cellulose is a key step in the processing of lignocellulosic biomass into bioethanol. Cellobiose, the disaccharide product of cellulose degradation, has been shown to inhibit cellulase activity, but the mechanisms underlying product inhibition are not clear. We combined single-molecule imaging and biochemical investigations with the goal of revealing the mechanism by which cellobiose inhibits the activity ofTrichoderma reeseiCel7A, a well-characterized exo-cellulase. We find that cellobiose slows the processive velocity of Cel7A and shortens the distance moved per encounter; effects that can be explained by cellobiose binding to the product release site of the enzyme. Cellobiose also strongly inhibits the binding of Cel7A to immobilized cellulose, with a K_iof 2.1 mM. The isolated catalytic domain (CD) of Cel7A was also inhibited to a similar degree by cellobiose, and binding of an isolated carbohydrate-binding module to cellulose was not inhibited by cellobiose, suggesting that cellobiose acts on the CD alone. Finally, cellopentaose inhibited Cel7A binding at micromolar concentrations without affecting the enzyme’s velocity of movement along cellulose. Together, these results suggest that cellobiose inhibits Cel7A activity both by binding to the “back door” product release site to slow activity and to the “front door” substrate-binding tunnel to inhibit interaction with cellulose. These findings point to strategies for engineering cellulases to reduce product inhibition and enhance cellulose degradation, supporting the growth of a sustainable bioeconomy. 

ABSTRACT Pectins are abundant in the cell walls of eudicot plants and have been implicated in determining the development and biomechanics of stomatal guard cells, which expand and contract dynamically to open and close stomatal pores on the plant surface, modulating photosynthesis and water transport. Pectic homogalacturonan is delivered to the cell wall in a methylesterified form but can be demethylesterified in the wall by pectin methylesterases, increasing both its ability to form crosslinks via calcium and its susceptibility to degradation by endogenous pectinases. Although a few pectin methylesterases have been implicated in stomatal development and function, this large family of proteins has not been fully characterized with respect to how they modulate stomatal guard cells. Here, we characterized the function of PECTIN METHYLESTERASE51 (PME51), a pectin methylesterase–encoding gene that is expressed in developing guard cells, in stomatal morphogenesis in seedlings and adult plants ofArabidopsis thaliana. OverexpressingPME51led to smaller adult plants with smaller stomatal complexes and subtle changes in initial responses to opening and closure stimuli, whereas knocking outPME51resulted in smaller stomatal complexes and longer roots in seedlings. We observed changes in pectin labeling in knockout and overexpression plants that imply a specific function for PME51 in modulating the degree of methylesterification for homogalacturonan. Together, these findings expand our understanding of how pectin modification by pectin methylesterases affects the development and function of stomatal guard cells, which must maintain a balance of strength and flexibility to optimize plant growth. 

Abstract Stomata are dynamic pores on plant surfaces that regulate photosynthesis and are thus of critical importance for understanding and leveraging the carbon-capturing and food-producing capabilities of plants. However, our understanding of the molecular underpinnings of stomatal kinetics and the biomechanical properties of the cell walls of stomatal guard cells that enable their dynamic responses to environmental and intrinsic stimuli is limited. Here, we built multiscale models that simulate regions of the guard cell wall, representing cellulose fibrils and matrix polysaccharides as discrete, interacting units, and used these models to help explain how molecular changes in wall composition and underlying architecture alter guard wall biomechanics that gives rise to stomatal responses in mutants with altered wall synthesis and modification. These results point to strategies for engineering guard cell walls to enhance stomatal response times and efficiency. 

Abstract BackgroundCellulose degradation by cellulases has been studied for decades due to the potential of using lignocellulosic biomass as a sustainable source of bioethanol. In plant cell walls, cellulose is bonded together and strengthened by the polyphenolic polymer, lignin. Because lignin is tightly linked to cellulose and is not digestible by cellulases, is thought to play a dominant role in limiting the efficient enzymatic degradation of plant biomass. Removal of lignin via pretreatments currently limits the cost-efficient production of ethanol from cellulose, motivating the need for a better understanding of how lignin inhibits cellulase-catalyzed degradation of lignocellulose. Work to date using bulk assays has suggested three possible inhibition mechanisms: lignin blocks access of the enzyme to cellulose, lignin impedes progress of the enzyme along cellulose, or lignin binds cellulases directly and acts as a sink. ResultsWe used single-molecule fluorescence microscopy to investigate the nanoscale dynamics of Cel7A fromTrichoderma reesei, as it binds to and moves along purified bacterial cellulose in vitro. Lignified cellulose was generated by polymerizing coniferyl alcohol onto purified bacterial cellulose, and the degree of lignin incorporation into the cellulose meshwork was analyzed by optical and electron microscopy. We found that Cel7A preferentially bound to regions of cellulose where lignin was absent, and that in regions of high lignin density, Cel7A binding was inhibited. With increasing degrees of lignification, there was a decrease in the fraction of Cel7A that moved along cellulose rather than statically binding. Furthermore, with increasing lignification, the velocity of processive Cel7A movement decreased, as did the distance that individual Cel7A molecules moved during processive runs. ConclusionsIn an in vitro system that mimics lignified cellulose in plant cell walls, lignin did not act as a sink to sequester Cel7A and prevent it from interacting with cellulose. Instead, lignin both blocked access of Cel7A to cellulose and impeded the processive movement of Cel7A along cellulose. This work implies that strategies for improving biofuel production efficiency should target weakening interactions between lignin and cellulose surface, and further suggest that nonspecific adsorption of Cel7A to lignin is likely not a dominant mechanism of inhibition.