scholarly journals Optimal reorganization of photosynthesis after the evolution of C4

2020 ◽  
Author(s):  
Haoran Zhou ◽  
Erol Akçay ◽  
Brent Helliker
Keyword(s):  
Electron Transport ◽  
Bundle Sheath ◽  
Lower Proportion ◽  
Cyclic Electron Transport ◽  
Linear Electron ◽  
Total Electron ◽  
Phylogenetic Studies ◽  
Bundle Sheath Cells ◽  
Great Progress ◽  
Photosynthetic Machinery

AbstractThe evolution of C4 photosynthesis evolved numerous times independently in the grasses over tens of millions of years, and each event required the development of distinct biochemistry and anatomy. Recent theoretical, anatomical and phylogenetic studies made great progress in reconstructing the evolutionary processes leading to the formation of the C4 carbon concentration mechanism (CCM) in grasses. After the formation of the full CCM, C4 physiology continued to diverge between C3 and C4 grasses, presumably as selection optimized photosynthetic function. In this study, we combine optimality modeling, physiological measurements and phylogenetic analysis to examine how various aspects of C4 photosynthetic machinery were reorganized within a lineage and as compared to closely-related C3 grasses. Both model and empirical results support a strong, and comparatively rapid, reorganization in resource allocation between the Calvin-Benson cycle and light reactions in C4, as determined by a higher maximal electron transport to maximal Rubisco carboxylation rate (Jmax/Vcmax). Our model, chlorophyll a/b ratios, and fluorescence-based electron transport measurements all suggest that linear electron transport represents a lower proportion (approximately 67%) of total electron transport in C4, and that the impetus for increased cyclic-electron transport is to balance ATP:NADPH stoichiometry, as opposed to decreasing O2 in the bundle sheath cells. Finally, the tight coordination between RuBP carboxylation and PEP carboxylation occurred coincidently with the evolution of the C4 CCM, with a relatively constant maximal PEP carboxylation rate and Vcmax (Vpmax/Vcmax).

scholarly journals The Physiological Functionality of PGR5/PGRL1-Dependent Cyclic Electron Transport in Sustaining Photosynthesis

2021 ◽  
Vol 12 ◽  
Author(s):  
Mingzhu Ma ◽  
Yifei Liu ◽  
Chunming Bai ◽  
Yunhong Yang ◽  
Zhiyu Sun ◽  
...  
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Nadh Dehydrogenase ◽  
Extreme Weather Events ◽  
Cyclic Electron Transport ◽  
Linear Electron ◽  
Transport Pathway ◽  
Biochemical Processes ◽  
Weather Events ◽  
Electron Transport Pathway

The cyclic electron transport (CET), after the linear electron transport (LET), is another important electron transport pathway during the light reactions of photosynthesis. The proton gradient regulation 5 (PGR5)/PRG5-like photosynthetic phenotype 1 (PGRL1) and the NADH dehydrogenase-like complex pathways are linked to the CET. Recently, the regulation of CET around photosystem I (PSI) has been recognized as crucial for photosynthesis and plant growth. Here, we summarized the main biochemical processes of the PGR5/PGRL1-dependent CET pathway and its physiological significance in protecting the photosystem II and PSI, ATP/NADPH ratio maintenance, and regulating the transitions between LET and CET in order to optimize photosynthesis when encountering unfavorable conditions. A better understanding of the PGR5/PGRL1-mediated CET during photosynthesis might provide novel strategies for improving crop yield in a world facing more extreme weather events with multiple stresses affecting the plants.

scholarly journals Improving Light Use Efficiency in C4 Plants by Increasing Electron Transport Rate

Proceedings ◽  
2020 ◽  
Vol 36 (1) ◽  
pp. 203
Author(s):  
Maria Ermakova ◽  
Robert T. Furbank ◽  
Susanne von Caemmerer
Keyword(s):  
Electron Transport ◽  
Conversion Efficiency ◽  
C4 Photosynthesis ◽  
Foxtail Millet ◽  
Bundle Sheath ◽  
C4 Plants ◽  
Crop Species ◽  
Bundle Sheath Cells ◽  
Light Conversion Efficiency ◽  
Sheath Cells

C4 plants play a key role in world agriculture and strategies to manipulate and enhance C4 photosynthesis have the potential for major agricultural impacts. The C4 photosynthetic pathway is a biochemical CO2 concentrating mechanism that requires the coordinated functioning of mesophyll and bundle sheath cells of leaves. Chloroplast electron transport in C4 plants is shared between the two cell types; it provides resources for CO2 fixation therefore underpinning the efficiency of photosynthesis. Using the model monocot C4 species Setaria viridis (green foxtail millet) we demonstrated that the Cytochrome (Cyt) b6f complex regulates the electron transport capacity and thus the rate of CO2 assimilation at high light and saturating CO2. Overexpression of the Cyt b6f in both mesophyll and bundle sheath cells results in a higher electron throughput and allows better light conversion efficiency in both photosystems. Importantly, increased Cyt b6f abundance in leaves provides higher rates of C4 photosynthesis without marked changes in Rubisco or chlorophyll content. Our results demonstrate that increasing the rate of electron transport is a viable strategy for improving the light conversion efficiency in C4 crop species like maize and sorghum.

scholarly journals Overexpression of the Rieske FeS protein of the Cytochromeb6fcomplex increases C4photosynthesis

2019 ◽  
Author(s):  
Maria Ermakova ◽  
Patricia E. Lopez-Calcagno ◽  
Christine A. Raines ◽  
Robert T. Furbank ◽  
Susanne von Caemmerer
Keyword(s):  
Electron Transport ◽  
Cell Types ◽  
Bundle Sheath ◽  
Assimilation Rate ◽  
Higher Plant ◽  
Bundle Sheath Cells ◽  
Electron Transport Chains ◽  
Photosynthetic Complexes ◽  
Rieske Fes Protein ◽  
Sheath Cells

AbstractC4plants contribute 20% to the global primary productivity despite representing only 4% of higher plant species. Their CO2concentrating mechanism operating between mesophyll and bundle sheath cells increases CO2partial pressure at the site of Rubisco and hence photosynthetic efficiency. Electron transport chains in both cell types supply ATP and NADPH for C4photosynthesis. Since Cytochromeb6fis a key point of control of electron transport in C3plants, we constitutively overexpressed the Rieske FeS subunit inSetaria viridisto study the effects on C4photosynthesis. Rieske FeS overexpression resulted in a higher content of Cytochromeb6fin both mesophyll and bundle sheath cells without marked changes in abundances of other photosynthetic complexes and Rubisco. Plants with higher Cytochromeb6fabundance showed better light conversion efficiency in both Photosystems and could generate higher proton-motive force across the thylakoid membrane. Rieske FeS abundance correlated with CO2assimilation rate and plants with a 10% increase in Rieske FeS content showed a 10% increase in CO2assimilation rate at ambient and saturating CO2and high light. Our results demonstrate that Cytochromeb6fcontrols the rate of electron transport in C4plants and that removing electron transport limitations can increase the rate of C4photosynthesis.

scholarly journals PGR5-PGRL1-Dependent Cyclic Electron Transport Modulates Linear Electron Transport Rate in Arabidopsis thaliana

2016 ◽  
Vol 9 (2) ◽  
pp. 271-288 ◽  
Author(s):  
Marjaana Suorsa ◽  
Fabio Rossi ◽  
Luca Tadini ◽  
Mathias Labs ◽  
Monica Colombo ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Electron Transport ◽  
Electron Transport Rate ◽  
Transport Rate ◽  
Cyclic Electron Transport ◽  
Linear Electron
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