scholarly journals From ecophysiology to phenomics: some implications of photoprotection and shade–sun acclimation in situ for dynamics of thylakoids in vitro

2012 ◽  
Vol 367 (1608) ◽  
pp. 3503-3514 ◽  
Author(s):  
Shizue Matsubara ◽  
Britta Förster ◽  
Melinda Waterman ◽  
Sharon A. Robinson ◽  
Barry J. Pogson ◽  
...  
Keyword(s):  
Membrane Dynamics ◽  
Persea Americana ◽  
Physiological Data ◽  
Photochemical Quenching ◽  
Shade Acclimation ◽  
Non Photochemical Quenching ◽  
Time Frames ◽  
Shade Leaves

Half a century of research into the physiology and biochemistry of sun–shade acclimation in diverse plants has provided reality checks for contemporary understanding of thylakoid membrane dynamics. This paper reviews recent insights into photosynthetic efficiency and photoprotection from studies of two xanthophyll cycles in old shade leaves from the inner canopy of the tropical trees Inga sapindoides and Persea americana (avocado). It then presents new physiological data from avocado on the time frames of the slow coordinated photosynthetic development of sink leaves in sunlight and on the slow renovation of photosynthetic properties in old leaves during sun to shade and shade to sun acclimation. In so doing, it grapples with issues in vivo that seem relevant to our increasingly sophisticated understanding of Δ pH-dependent, xanthophyll-pigment-stabilized non-photochemical quenching in the antenna of PSII in thylakoid membranes in vitro .

scholarly journals Identification of parallel pH- and zeaxanthin-dependent quenching of excess energy in LHCSR3 in Chlamydomonas reinhardtii

2020 ◽  
Author(s):  
Julianne M. Troiano ◽  
Federico Perozeni ◽  
Raymundo Moya ◽  
Luca Zuliani ◽  
Kwangryul Baek ◽  
...  
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Light Harvesting ◽  
Complex Stress ◽  
Excess Energy ◽  
Photochemical Quenching ◽  
Light Harvesting Complexes ◽  
Light Harvesting Complex ◽  
Non Photochemical Quenching

AbstractUnder high light conditions, oxygenic photosynthetic organisms avoid photodamage by thermally dissipating excess absorbed energy, which is called non-photochemical quenching (NPQ). In green algae, a chlorophyll and carotenoid-binding protein, light-harvesting complex stress-related (LHCSR3), detects excess energy via pH and serves as a quenching site. However, the mechanisms by which LHCSR3 functions have not been determined. Using a combined in vivo and in vitro approach, we identify two parallel yet distinct quenching processes, individually controlled by pH and carotenoid composition, and their likely molecular origin within LHCSR3 from Chlamydomonas reinhardtii. The pH-controlled quenching is removed within a mutant LHCSR3 that lacks the protonable residues responsible for sensing pH. Constitutive quenching in zeaxanthin-enriched systems demonstrates zeaxanthin-controlled quenching, which may be shared with other light-harvesting complexes. We show that both quenching processes prevent the formation of damaging reactive oxygen species, and thus provide distinct timescales and mechanisms of protection in a changing environment.

scholarly journals Allosteric regulation of the light-harvesting system of photosystem II

2000 ◽  
Vol 355 (1402) ◽  
pp. 1361-1370 ◽  
Author(s):  
Peter Horton ◽  
Alexander V. Ruban ◽  
Mark Wentworth
Keyword(s):  
Photosystem Ii ◽  
Xanthophyll Cycle ◽  
Light Harvesting ◽  
Allosteric Regulation ◽  
Photochemical Quenching ◽  
Protein Subunit ◽  
Ps Ii ◽  
Non Photochemical Quenching

Non–photochemical quenching of chlorophyll fluorescence (NPQ) is symptomatic of the regulation of energy dissipation by the light–harvesting antenna of photosystem II (PS II). The kinetics of NPQ in both leaves and isolated chloroplasts are determined by the transthylakoid ΔpH and the de–epoxidation state of the xanthophyll cycle. In order to understand the mechanism and regulation of NPQ we have adopted the approaches commonly used in the study of enzyme–catalysed reactions. Steady–state measurements suggest allosteric regulation of NPQ, involving control by the xanthophyll cycle carotenoids of a protonationdependent conformational change that transforms the PS II antenna from an unquenched to a quenched state. The features of this model were confirmed using isolated light–harvesting proteins. Analysis of the rate of induction of quenching both in vitro and in vivo indicated a bimolecular second–order reaction; it is suggested that quenching arises from the reaction between two fluorescent domains, possibly within a single protein subunit. A universal model for this transition is presented based on simple thermodynamic principles governing reaction kinetics.

scholarly journals Antenna Protein Clustering In Vitro Unveiled by Fluorescence Correlation Spectroscopy

2021 ◽  
Vol 22 (6) ◽  
pp. 2969
Author(s):  
Aurélie Crepin ◽  
Edel Cunill-Semanat ◽  
Eliška Kuthanová Trsková ◽  
Erica Belgio ◽  
Radek Kaňa
Keyword(s):  
Fluorescence Correlation Spectroscopy ◽  
Higher Plants ◽  
Fluorescence Emission ◽  
Correlation Spectroscopy ◽  
Photochemical Quenching ◽  
High Ph ◽  
Fluorescence Correlation ◽  
Non Photochemical Quenching

Antenna protein aggregation is one of the principal mechanisms considered effective in protecting phototrophs against high light damage. Commonly, it is induced, in vitro, by decreasing detergent concentration and pH of a solution of purified antennas; the resulting reduction in fluorescence emission is considered to be representative of non-photochemical quenching in vivo. However, little is known about the actual size and organization of antenna particles formed by this means, and hence the physiological relevance of this experimental approach is questionable. Here, a quasi-single molecule method, fluorescence correlation spectroscopy (FCS), was applied during in vitro quenching of LHCII trimers from higher plants for a parallel estimation of particle size, fluorescence, and antenna cluster homogeneity in a single measurement. FCS revealed that, below detergent critical micelle concentration, low pH promoted the formation of large protein oligomers of sizes up to micrometers, and therefore is apparently incompatible with thylakoid membranes. In contrast, LHCII clusters formed at high pH were smaller and homogenous, and yet still capable of efficient quenching. The results altogether set the physiological validity limits of in vitro quenching experiments. Our data also support the idea that the small, moderately quenching LHCII oligomers found at high pH could be relevant with respect to non-photochemical quenching in vivo.

scholarly journals Structure of SOQ1 lumenal domains identifies potential disulfide exchange for negative regulation of photoprotection, qH

2021 ◽  
Author(s):  
Guimei Yu ◽  
Xiaowei Pan ◽  
Jingfang Hao ◽  
Lifang Shi ◽  
Yong Zhang ◽  
...  
Keyword(s):  
Biochemical Characterization ◽  
Photochemical Quenching ◽  
Interface Residue ◽  
Domain Interaction ◽  
Disulfide Exchange ◽  
Redox Active ◽  
Non Photochemical Quenching

Non-photochemical quenching (NPQ) plays an important role for phototrophs in decreasing photo-oxidative damage. qH is a sustained component of NPQ and depends on the plastid lipocalin (LCNP). A thylakoid membrane-anchored protein SUPPRESSOR OF QUENCHING1 (SOQ1) prevents qH formation by inhibiting LCNP. SOQ1 suppresses qH with its lumen-located C-terminal Trx-like and NHL domains. Here we report crystal structures and biochemical characterization of SOQ1 lumenal domains. Our results show that the Trx-like and NHL domains are stably associated, with the potential redox-active motif located at their interface. Residue E859 essential for SOQ1 function is pivotal for mediating the inter-domain interaction. Moreover, the C-terminal region of SOQ1 forms an independent -stranded domain, which possibly interacts with the Trx-like domain through disulfide exchange. Furthermore, SOQ1 is susceptible to cleavage at the loops connecting the neighboring domains both in vitro and in vivo, which could be a regulatory process for its suppression function of qH.

Regulation of plant light harvesting by thermal dissipation of excess energy

2010 ◽  
Vol 38 (2) ◽  
pp. 651-660 ◽  
Author(s):  
Silvia de Bianchi ◽  
Matteo Ballottari ◽  
Luca Dall’Osto ◽  
Roberto Bassi
Keyword(s):  
Higher Plants ◽  
Current Knowledge ◽  
Protein Complexes ◽  
Thermal Dissipation ◽  
Photochemical Quenching ◽  
Knockout Mutants ◽  
Pigment Protein Complexes ◽  
Non Photochemical Quenching

Elucidating the molecular details of qE (energy quenching) induction in higher plants has proven to be a major challenge. Identification of qE mutants has provided initial information on functional elements involved in the qE mechanism; furthermore, investigations on isolated pigment–protein complexes and analysis in vivo and in vitro by sophisticated spectroscopic methods have been used for the elucidation of mechanisms involved. The aim of the present review is to summarize the current knowledge of the phenotype of npq (non-photochemical quenching)-knockout mutants, the role of gene products involved in the qE process and compare the molecular models proposed for this process.

Aqueous extracts of avocado pear (Persea americana Mill.) leaves and seeds exhibit anti-cholinesterases and antioxidant activities in vitro

2016 ◽  
Vol 27 (2) ◽  
Author(s):  
Ganiyu Oboh ◽  
Veronica O. Odubanjo ◽  
Fatai Bello ◽  
Ayokunle O. Ademosun ◽  
Sunday I. Oyeleye ◽  
...  
Keyword(s):  
Leaf Extract ◽  
Antioxidant Activities ◽  
Radical Scavenging ◽  
Inhibitory Effect ◽  
Seed Extract ◽  
Persea Americana ◽  
Dependent Manner ◽  
Natural Treatment

AbstractAvocado pear (The inhibitory effects of extracts on AChE and BChE activities and antioxidant potentials (inhibition of FeThe extracts inhibited AChE and BChE activities and prooxidant-induced TBARS production in a dose-dependent manner, with the seed extract having the highest inhibitory effect and the leaf extract exhibiting higher phenolic content and radical scavenging abilities, but lower Fe chelation ability compared with that of the seed. The phytochemical screening revealed the presence of saponins, alkaloids, and terpenoids in both extracts, whereas the total alkaloid profile was higher in the seed extract than in the leaf extract, as revealed by GC-FID.The anti-cholinesterase and antioxidant activities of avocado leaf and seed could be linked to their phytoconstituents and might be the possible mechanisms underlying their use as a cheap and natural treatment/management of AD. However, these extracts should be further investigated in vivo.

Dynamic organization of the mitochondrial protein import machinery

2016 ◽  
Vol 397 (11) ◽  
pp. 1097-1114 ◽  
Author(s):  
Sebastian P. Straub ◽  
Sebastian B. Stiller ◽  
Nils Wiedemann ◽  
Nikolaus Pfanner
Keyword(s):  
Mitochondrial Membrane ◽  
Protein Import ◽  
Mitochondrial Protein ◽  
Membrane Dynamics ◽  
Intermembrane Space ◽  
Mitochondrial Protein Import ◽  
Precursor Proteins ◽  
Dynamic Cooperation

Abstract Mitochondria contain elaborate machineries for the import of precursor proteins from the cytosol. The translocase of the outer mitochondrial membrane (TOM) performs the initial import of precursor proteins and transfers the precursors to downstream translocases, including the presequence translocase and the carrier translocase of the inner membrane, the mitochondrial import and assembly machinery of the intermembrane space, and the sorting and assembly machinery of the outer membrane. Although the protein translocases can function as separate entities in vitro, recent studies revealed a close and dynamic cooperation of the protein import machineries to facilitate efficient transfer of precursor proteins in vivo. In addition, protein translocases were found to transiently interact with distinct machineries that function in the respiratory chain or in the maintenance of mitochondrial membrane architecture. Mitochondrial protein import is embedded in a regulatory network that ensures protein biogenesis, membrane dynamics, bioenergetic activity and quality control.

Efficacy of Potential Control Agents Against Rosellinia necatrix and Their Physiological Impact on Avocado

Plant Disease ◽  
2021 ◽  
Author(s):  
Phinda Magagula ◽  
Nicky Taylor ◽  
Velushka Swart ◽  
Noëlani van den Berg
Keyword(s):  
Integrated Management ◽  
Integrated Approach ◽  
Dry Mass ◽  
Persea Americana ◽  
Effective Control ◽  
Rosellinia Necatrix ◽  
Potential Control ◽  
Greenhouse Trial

Rosellinia necatrix is the causal agent of white root rot (WRR), a fatal disease affecting many woody plants, including avocado (Persea americana). As with other root diseases, an integrated approach is required to control WRR. No fully effective control methods are available, and no chemical or biological agents against R. necatrix have been registered for use on avocado in South Africa. Fluazinam has shown promising results in the greenhouse and field in other countries, including Spain. The current study aimed to investigate the potential of a fumigant, chloropicrin, and biological control agents (B-Rus, Beta-Bak, Mity-Gro, and Trichoderma) against R. necatrix both in vitro and in vivo as compared with fluazinam. In a greenhouse trial, results showed that Trichoderma and B-Rus were as effective as fluazinam at inhibiting R. necatrix in vitro and suppressed WRR symptoms when applied before inoculation with R. necatrix. In contrast, Mity-Gro and Beta-Bak failed to inhibit the pathogen in vitro and in the greenhouse trial, despite application of the products to plants before R. necatrix infection. Fluazinam suppressed WRR symptoms in plants when applied at the early stages of infection, whereas chloropicrin rendered the pathogen nonviable when used as a preplant treatment. Plants treated with Trichoderma, B-Rus, and fluazinam sustained dry mass production and net CO2 assimilation by maintaining the green leaf tissues despite being infected with the pathogen. This study has important implications for the integrated management of WRR.

Glucose homeostasis and hypothalamic-pituitary-adrenocortical axis during development in rats

1990 ◽  
Vol 259 (5) ◽  
pp. E601-E613 ◽  
Author(s):  
E. P. Widmaier
Keyword(s):  
Stress Responses ◽  
Adrenocorticotropic Hormone ◽  
Glucose Sensor ◽  
Adult Life ◽  
Glucose Sensing ◽  
Physiological Data ◽  
Compensatory Mechanisms ◽  
Definition Of

Glucoprivation represents a model stress in which activation of different stress responses at different ages can be monitored both in vivo and in vitro. Physiological data indicate rat brain contains a liver/pancreas-type glucose sensor, yet no biochemical or immunocytochemical evidence exists for such a sensor. Young rats appear to lack normal hypothalamic glucose-sensing ability and do not show typical secretory patterns of corticotropin-releasing factor, adrenocorticotropic hormone, or corticosterone after experimentally induced glucoprivation. However, they hypersecrete catecholamines and glucagon (compared with adults) and thrive on fuel sources other than glucose that are abundant after birth. High steroid levels during the first 24 h after birth may be critical for inducing gluconeogenic enzymes and promoting differentiation of tissues like pancreas. Neonatal rats also have unique control systems to combat the damaging effects of other stresses like hypoxia; these systems may disappear in adults. Thus the definition of stress may change during development, and the compensatory mechanisms employed to combat stress change from neonatal to adult life and are intricately related to the metabolic needs of the animal.

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