scholarly journals Expression of a CO2-permeable aquaporin enhances mesophyll conductance in the C4 species Setaria viridis

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Maria Ermakova ◽  
Hannah Osborn ◽  
Michael Groszmann ◽  
Soumi Bala ◽  
Andrew Bowerman ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Carbon Fixation ◽  
Foxtail Millet ◽  
Mesophyll Conductance ◽  
Mesophyll Cells ◽  
Green Foxtail ◽  
Targeted Expression ◽  
Fundamental Limitation ◽  
Leaf Biochemistry

A fundamental limitation of photosynthetic carbon fixation is the availability of CO2. In C4 plants, primary carboxylation occurs in mesophyll cytosol, and little is known about the role of CO2 diffusion in facilitating C4 photosynthesis. We have examined the expression, localization, and functional role of selected plasma membrane intrinsic aquaporins (PIPs) from Setaria italica (foxtail millet) and discovered that SiPIP2;7 is CO2-permeable. When ectopically expressed in mesophyll cells of S. viridis (green foxtail), SiPIP2;7 was localized to the plasma membrane and caused no marked changes in leaf biochemistry. Gas-exchange and C18O16O discrimination measurements revealed that targeted expression of SiPIP2;7 enhanced the conductance to CO2 diffusion from the intercellular airspace to the mesophyll cytosol. Our results demonstrate that mesophyll conductance limits C4 photosynthesis at low pCO2 and that SiPIP2;7 is a functional CO2 permeable aquaporin that can improve CO2 diffusion at the airspace/mesophyll interface and enhance C4 photosynthesis.

scholarly journals Expression of a CO2-permeable aquaporin enhances mesophyll conductance in the C4 species Setaria viridis

2021 ◽  
Author(s):  
Maria Ermakova ◽  
Hannah Osborn ◽  
Michael Groszmann ◽  
Soumi Bala ◽  
Samantha McGaughey ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Carbon Fixation ◽  
Foxtail Millet ◽  
Mesophyll Conductance ◽  
Mesophyll Cells ◽  
Green Foxtail ◽  
Targeted Expression ◽  
Fundamental Limitation ◽  
Leaf Biochemistry

AbstractA fundamental limitation of photosynthetic carbon fixation is the availability of CO4. In C4 plants, primary carboxylation occurs in mesophyll cytosol, and little is known about the role of CO2 diffusion in facilitating C4 photosynthesis. We have examined the expression, localization, and functional role of selected plasma membrane intrinsic aquaporins (PIPs) from Setaria italica (foxtail millet) and discovered that SiPIP2;7 is CO2-permeable. When ectopically expressed in mesophyll cells of S. viridis (green foxtail), SiPIP2;7 was localized to the plasma membrane and caused no marked changes in leaf biochemistry. Gas-exchange and C18O16O discrimination measurements revealed that targeted expression of SiPIP2;7 enhanced the conductance to CO2 diffusion from the intercellular airspace to the mesophyll cytosol. Our results demonstrate that mesophyll conductance limits C4 photosynthesis at low pCO2 and that SiPIP2;7 is a functional CO2 permeable aquaporin that can improve CO2 diffusion at the airspace/mesophyll interface and enhance C4 photosynthesis.

The role of photosynthetic activity in the response of isolated Glycine max mesophyll cells to ozone

1988 ◽  
Vol 66 (4) ◽  
pp. 745-749 ◽  
Author(s):  
J. A. Omielan ◽  
E. J. Pell
Keyword(s):  
Glycine Max ◽  
Cell Viability ◽  
Cellular Response ◽  
Carbon Fixation ◽  
Mesophyll Cells ◽  
Before And After ◽  
Glycine Max L ◽  
Relative Cell Viability ◽  
In Cells

The hypothesis that active photosynthesis results in a more severe cellular response to ozone (O3) was tested. Using suspensions of isolated soybean (Glycine max (L.) Merr. cv. Chippewa 64) mesophyll cells, we measured photosynthetic carbon fixation rates and cell viability, as determined by fluorescein diacetate staining, before and after treatment with O3 in the light and dark in the presence or absence of NaHCO3. Ozone reduced the photosynthesis rates of isolated mesophyll cells to a greater degree than cell viability, suggesting greater sensitivity of photosynthesis. Posttreatment photosynthesis rates were higher in cells that were fumigated in media containing NaHCO3 than in cells fumigated in its absence. The only interaction detected was between the gaseous treatments and light, in which relative cell viability was reduced more by O3 in the light than in the dark, in the second experiment. The interaction was, at least in part, a reflection of experimental error. Of greater significance was the observation that the photosynthetic function could be affected equally by O3 in the dark and in the light.

Stationary organization of the actin cytoskeleton in Vallisneria: the role of stable microfilaments at the end walls

1995 ◽  
Vol 108 (4) ◽  
pp. 1531-1539
Author(s):  
J.H. Ryu ◽  
S. Takagi ◽  
R. Nagai
Keyword(s):  
Plasma Membrane ◽  
Actin Cytoskeleton ◽  
Cytoplasmic Streaming ◽  
Cytochalasin B ◽  
Prior Treatment ◽  
Aquatic Angiosperm ◽  
Mesophyll Cells ◽  
Complicated Process ◽  
Side Walls

In mesophyll cells of the aquatic angiosperm Vallisneria gigantea, bundles of microfilaments (MFs) serve as tracks for the rotational streaming of the cytoplasm, which occurs along the two longer side walls and the two shorter end walls. The stationary organization of these bundles has been shown to depend on the association of the bundles with the plasma membrane at the end walls. To identify the sites of such association, the effects of cytochalasin B (CB) on the configuration of the bundles of MFs were examined. In the case of the side walls, MFs were completely disrupted after treatment with CB at 100 micrograms/ml for 24 hours. By contrast, in the case of the end walls, a number of partially disrupted MFs remained even after 48 hours of treatment. After removal of CB, a completely normal arrangement of bundles of MFs was once again evident within 24 hours after a rather complicated process of reassembly. When reassembly had been completed, the direction of cytoplasmic streaming was reversed only in a small fraction of the treated cells, suggesting that bundles of MFs are anchored and stabilized at the end walls of each cell and that the polarity of reorganized bundles and, therefore, the direction of the cytoplasmic streaming is determined in a manner that depends on the original polarity of MFs that remained in spite of the disruptive action of CB. By contrast, the direction of reinitiated cytoplasmic streaming was reversed in 50% of cells in which the bundles of MFs had been completely disrupted by exogenously applied trypsin prior treatment with CB.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Channelrhodopsin-mediated optogenetics highlights a central role of depolarization-dependent plant proton pumps

2020 ◽  
Vol 117 (34) ◽  
pp. 20920-20925 ◽  
Author(s):  
Antonella Reyer ◽  
Melanie Häßler ◽  
Sönke Scherzer ◽  
Shouguang Huang ◽  
Jesper Torbøl Pedersen ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Membrane Potential ◽  
Blue Light ◽  
Functional Anatomy ◽  
Functional Expression ◽  
Proton Pumps ◽  
Mesophyll Cells ◽  
Protein Biochemistry ◽  
Electrical Signaling

In plants, environmental stressors trigger plasma membrane depolarizations. Being electrically interconnected via plasmodesmata, proper functional dissection of electrical signaling by electrophysiology is basically impossible. The green algaChlamydomonas reinhardtiievolved blue light-excited channelrhodopsins (ChR1, 2) to navigate. When expressed in excitable nerve and muscle cells, ChRs can be used to control the membrane potential via illumination. InArabidopsisplants, we used the algal ChR2-light switches as tools to stimulate plasmodesmata-interconnected photosynthetic cell networks by blue light and monitor the subsequent plasma membrane electrical responses. Blue-dependent stimulations of ChR2 expressing mesophyll cells, resting around −160 to −180 mV, reproducibly depolarized the membrane potential by 95 mV on average. Following excitation, mesophyll cells recovered their prestimulus potential not without transiently passing a hyperpolarization state. By combining optogenetics with voltage-sensing microelectrodes, we demonstrate that plant plasma membrane AHA-type H+-ATPase governs the gross repolarization process. AHA2 protein biochemistry and functional expression analysis inXenopusoocytes indicates that the capacity of this H+pump to recharge the membrane potential is rooted in its voltage- and pH-dependent functional anatomy. Thus, ChR2 optogenetics appears well suited to noninvasively expose plant cells to signal specific depolarization signatures. From the responses we learn about the molecular processes, plants employ to channel stress-associated membrane excitations into physiological responses.

Mesophyll conductance: the leaf corridors for photosynthesis

2020 ◽  
Vol 48 (2) ◽  
pp. 429-439 ◽  
Author(s):  
Jorge Gago ◽  
Danilo M. Daloso ◽  
Marc Carriquí ◽  
Miquel Nadal ◽  
Melanie Morales ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Current Knowledge ◽  
Main Role ◽  
Mesophyll Conductance ◽  
Future Studies ◽  
Cell Structures ◽  
Leaf Tissues ◽  
Change Framework ◽  
Chloroplast Stroma

Besides stomata, the photosynthetic CO2 pathway also involves the transport of CO2 from the sub-stomatal air spaces inside to the carboxylation sites in the chloroplast stroma, where Rubisco is located. This pathway is far to be a simple and direct way, formed by series of consecutive barriers that the CO2 should cross to be finally assimilated in photosynthesis, known as the mesophyll conductance (gm). Therefore, the gm reflects the pathway through different air, water and biophysical barriers within the leaf tissues and cell structures. Currently, it is known that gm can impose the same level of limitation (or even higher depending of the conditions) to photosynthesis than the wider known stomata or biochemistry. In this mini-review, we are focused on each of the gm determinants to summarize the current knowledge on the mechanisms driving gm from anatomical to metabolic and biochemical perspectives. Special attention deserve the latest studies demonstrating the importance of the molecular mechanisms driving anatomical traits as cell wall and the chloroplast surface exposed to the mesophyll airspaces (Sc/S) that significantly constrain gm. However, even considering these recent discoveries, still is poorly understood the mechanisms about signaling pathways linking the environment a/biotic stressors with gm responses. Thus, considering the main role of gm as a major driver of the CO2 availability at the carboxylation sites, future studies into these aspects will help us to understand photosynthesis responses in a global change framework.

Role of Exosomes in the Exchange of Spermatozoa after Leaving the Seminiferous Tubule: A Review

2020 ◽  
Vol 21 (5) ◽  
pp. 330-338
Author(s):  
Luming Wu ◽  
Yuan Ding ◽  
Shiqiang Han ◽  
Yiqing Wang
Keyword(s):  
Drug Delivery ◽  
Plasma Membrane ◽  
Seminiferous Tubule ◽  
Metabolic Diseases ◽  
Inflammatory Diseases ◽  
Multivesicular Bodies ◽  
Extensive Search ◽  
Neurological Research ◽  
The One

Background: Exosomes are extracellular vesicles (EVs) released from cells upon fusion of an intermediate endocytic compartment with the plasma membrane. They refer to the intraluminal vesicles released from the fusion of multivesicular bodies with the plasma membrane. The contents and number of exosomes are related to diseases such as metabolic diseases, cancer and inflammatory diseases. Exosomes have been used in neurological research as a drug delivery tool and also as biomarkers for diseases. Recently, exosomes were observed in the seminal plasma of the one who is asthenozoospermia, which can affect sperm motility and capacitation. Objective: The main objective of this review is to deeply discuss the role of exosomes in spermatozoa after leaving the seminiferous tubule. Methods: We conducted an extensive search of the literature available on relationships between exosomes and exosomes in spermatozoa on the bibliographic database. Conclusion: : This review thoroughly discussed the role that exosomes play in the exchange of spermatozoa after leaving the seminiferous tubule and its potential as a drug delivery tool and biomarkers for diseases as well.

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