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Abstracts of Articles in 2024
To request any journal reprints, please contact us.- CO2 Response Screen in Grass Brachypodium Reveals Shows Key Role of a MAP-kinase in CO2-induced Stomatal Closure.
- Targeting Tuberculosis: Novel Scaffolds for Inhibiting Cytochrome bd Oxidase.
- Dilated cardiomyopathy mutation in beta-cardiac myosin enhances actin activation of the power stroke and phosphate release.
- Multiscale modeling shows that 2-deoxy-ATP improves ventricular function by modulating calcium cycling, crossbridge kinetics, and myosin recruitment.
CO2 Response Screen in Grass Brachypodium Reveals Shows Key Role of a MAP-kinase in CO2-induced Stomatal Closure.Plant Physiology, to appear (2024).
Plants respond to increased CO2 concentrations through rapid stomatal closure which can contribute to increased water use efficiency. Grasses display faster stomatal responses than eudicots due to dumbbell-shaped guard cells flanked by subsidiary cells working in opposition. However, forward genetic screening for stomatal CO2 signal transduction mutants in grasses has not been reported. The grass model Brachypodium distachyon is closely related to agronomically important cereal crops, sharing largely collinear genomes. To gain insights into CO2 control mechanisms of stomatal movements in grasses, we developed a forward genetics screen with an EMS-mutagenized Brachypodium distachyon M5 generation population using infrared imaging to identify plants with altered canopy leaf temperature at elevated CO2. Among isolated mutants, a “chill1” mutant exhibited cooler leaf temperatures than wildtype Bd21-3 parent control plants after exposure to increased [CO2]. chill1 plants showed strongly impaired high CO2-induced stomatal closure, despite retaining a robust abscisic acid-induced stomatal closing response. Through bulked segregant whole-genome-sequencing analyses followed by analyses of further backcrossed F4 generation plants and generation and characterization of CRISPR-cas9 mutants, chill1 was mapped to a protein kinase, BdMPK5. The chill1 mutation impaired BdMPK5 protein-mediated CO2/HCO3- sensing in vitro. Furthermore, AlphaFold2-directed structural modeling suggests that the identified BdMPK5-D90N chill1 mutant residue is located at the interface with the HT1 Raf-like kinase. BdMPK5 is a key signaling component involved in CO2-induced stomatal movements, potentially functioning as a component of the CO2 sensor in grasses.
Plants respond to increased CO2 concentrations through rapid stomatal closure which can contribute to increased water use efficiency. Grasses display faster stomatal responses than eudicots due to dumbbell-shaped guard cells flanked by subsidiary cells working in opposition. However, forward genetic screening for stomatal CO2 signal transduction mutants in grasses has not been reported. The grass model Brachypodium distachyon is closely related to agronomically important cereal crops, sharing largely collinear genomes. To gain insights into CO2 control mechanisms of stomatal movements in grasses, we developed a forward genetics screen with an EMS-mutagenized Brachypodium distachyon M5 generation population using infrared imaging to identify plants with altered canopy leaf temperature at elevated CO2. Among isolated mutants, a “chill1” mutant exhibited cooler leaf temperatures than wildtype Bd21-3 parent control plants after exposure to increased [CO2]. chill1 plants showed strongly impaired high CO2-induced stomatal closure, despite retaining a robust abscisic acid-induced stomatal closing response. Through bulked segregant whole-genome-sequencing analyses followed by analyses of further backcrossed F4 generation plants and generation and characterization of CRISPR-cas9 mutants, chill1 was mapped to a protein kinase, BdMPK5. The chill1 mutation impaired BdMPK5 protein-mediated CO2/HCO3- sensing in vitro. Furthermore, AlphaFold2-directed structural modeling suggests that the identified BdMPK5-D90N chill1 mutant residue is located at the interface with the HT1 Raf-like kinase. BdMPK5 is a key signaling component involved in CO2-induced stomatal movements, potentially functioning as a component of the CO2 sensor in grasses.
Targeting Tuberculosis: Novel Scaffolds for Inhibiting Cytochrome bd Oxidase.J. Chem. Info. Model., to appear (2024).
Dilated cardiomyopathy mutation in beta-cardiac myosin enhances actin activation of the power stroke and phosphate release.PNAS Nexus to appear (2024).
Multiscale modeling shows that 2-deoxy-ATP improves ventricular function by modulating calcium cycling, crossbridge kinetics, and myosin recruitment.Proc. Natl. Acad. Sci. USA, to appear (2024).
2'-deoxy-ATP (dATP) improves cardiac function by increasing the rate of crossbridge cycling and Ca[Formula: see text] transient decay. However, the mechanisms of these effects and how therapeutic responses to dATP are achieved when dATP is only a small fraction of the total ATP pool remain poorly understood. Here, we used a multiscale computational modeling approach to analyze the mechanisms by which dATP improves ventricular function. We integrated atomistic simulations of prepowerstroke myosin and actomyosin association, filament-scale Markov state modeling of sarcomere mechanics, cell-scale analysis of myocyte Ca[Formula: see text] dynamics and contraction, organ-scale modeling of biventricular mechanoenergetics, and systems level modeling of circulatory dynamics. Molecular and Brownian dynamics simulations showed that dATP increases the actomyosin association rate by 1.9 fold. Markov state models predicted that dATP increases the pool of myosin heads available for crossbridge cycling, increasing steady-state force development at low dATP fractions by 1.3 fold due to mechanosensing and nearest-neighbor cooperativity. This was found to be the dominant mechanism by which small amounts of dATP can improve contractile function at myofilament to organ scales. Together with faster myocyte Ca[Formula: see text] handling, this led to improved ventricular contractility, especially in a failing heart model in which dATP increased ejection fraction by 16% and the energy efficiency of cardiac contraction by 1%. This work represents a complete multiscale model analysis of a small molecule myosin modulator from single molecule to organ system biophysics and elucidates how the molecular mechanisms of dATP may improve cardiovascular function in heart failure with reduced ejection fraction.
2'-deoxy-ATP (dATP) improves cardiac function by increasing the rate of crossbridge cycling and Ca[Formula: see text] transient decay. However, the mechanisms of these effects and how therapeutic responses to dATP are achieved when dATP is only a small fraction of the total ATP pool remain poorly understood. Here, we used a multiscale computational modeling approach to analyze the mechanisms by which dATP improves ventricular function. We integrated atomistic simulations of prepowerstroke myosin and actomyosin association, filament-scale Markov state modeling of sarcomere mechanics, cell-scale analysis of myocyte Ca[Formula: see text] dynamics and contraction, organ-scale modeling of biventricular mechanoenergetics, and systems level modeling of circulatory dynamics. Molecular and Brownian dynamics simulations showed that dATP increases the actomyosin association rate by 1.9 fold. Markov state models predicted that dATP increases the pool of myosin heads available for crossbridge cycling, increasing steady-state force development at low dATP fractions by 1.3 fold due to mechanosensing and nearest-neighbor cooperativity. This was found to be the dominant mechanism by which small amounts of dATP can improve contractile function at myofilament to organ scales. Together with faster myocyte Ca[Formula: see text] handling, this led to improved ventricular contractility, especially in a failing heart model in which dATP increased ejection fraction by 16% and the energy efficiency of cardiac contraction by 1%. This work represents a complete multiscale model analysis of a small molecule myosin modulator from single molecule to organ system biophysics and elucidates how the molecular mechanisms of dATP may improve cardiovascular function in heart failure with reduced ejection fraction.
