scholarly journals Photosynthetic Responses of Canola to Exogenous Application or Endogenous Overproduction of 5-Aminolevulinic Acid (ALA) under Various Nitrogen Levels

Plants ◽  
2020 ◽  
Vol 9 (11) ◽  
pp. 1419
Author(s):  
Xinxin Feng ◽  
Yuyan An ◽  
Jingjing Gao ◽  
Liangju Wang
Keyword(s):  
Chlorophyll Fluorescence ◽  
Aminolevulinic Acid ◽  
Oxygen Evolving Complex ◽  
Wild Type ◽  
Brassica Napus L ◽  
Ps Ii ◽  
Chlorophyll Contents ◽  
N Level ◽  
Photosynthetic Responses ◽  
Prompt Chlorophyll Fluorescence

Limited data are available on the effects of 5-aminolevulinic acid (ALA) on plant photosynthesis in relation to the nitrogen (N) level. In this study, we investigate photosynthetic responses to ALA in canola plants (Brassica napus L.). We used wild-type plants without ALA addition (controls), wild-type plants with exogenous ALA application, and transgenic plants that endogenously overproduced ALA. The plants were grown hydroponically in nutrient solutions with low, middle, and high concentrations of N. Our results indicate that plants in both treatment groups had higher chlorophyll contents and net photosynthetic rates and lower intracellular CO2 concentrations in the leaves, as compared to controls. Furthermore, simultaneous measurement of prompt chlorophyll fluorescence and modulated 820-nm reflections showed that the active photosystem II (PS II) reaction centers, electron transfer capacity, and photosystem I (PS I) activity were all higher in treated plants than controls at all N levels; however, the responses of some photochemical processes to ALA were significantly affected by the N level. For example, under low N conditions only, a negative ΔK peak appeared in the prompt chlorophyll fluorescence curve, indicating a protective effect of ALA on electron donation via activation of the oxygen-evolving complex. Taken together, our findings suggest that ALA contributes to the promotion of photosynthesis by regulating photosynthetic electron transport under various N levels. These findings may provide a new strategy for improving photosynthesis in crops grown in N-poor conditions or reduced N-fertilization requirements.

scholarly journals Photosystem II: Thermodynamics and Kinetics of Electron Transport from QA- to QB(QB- ) and Deleterious Effects of Copper(II)

1993 ◽  
Vol 48 (3-4) ◽  
pp. 234-240 ◽  
Author(s):  
G. Renger ◽  
H. M. Gleiter ◽  
E. Haag ◽  
F. Reifarth
Keyword(s):  
Oxygen Evolution ◽  
Manganese Content ◽  
Fluorescence Emission ◽  
Laser Flash ◽  
Fluorescence Induction ◽  
Oxygen Evolving Complex ◽  
Ps Ii ◽  
Thermodynamics And Kinetics ◽  
Redox Active ◽  
Kinetics Of

Studies on thermodynamics and kinetics of electron transfer from QA- to QB(QB-) were performed by monitoring laser flash induced changes of the relative fluorescence emission as a function of temperature (220 K < T < 310 K) in isolated thylakoids and PS II membrane fragments.In addition, effects of bivalent metal ions on PS II were investigated by measuring conventional fluorescence induction curves, oxygen evolution, manganese content and atrazine binding mostly in PS II membrane fragments. It was found: a) the normalized level of the fluorescence remaining 10 s after the actinic flash (Ft/F0) steeply increases at temperatures below -10 to - 20 °C, b) the fast phase of the transient fluorescence change becomes markedly retarded with decreasing temperatures, c) among different cations (Cu2+, Zn2+, Cd2+, Ni2+, Co2+) only Cu2+ exhibits marked effects in the concentration range below 100 μᴍ and d) Cu2+ decreases the normalized variable fluorescence, inhibits oxygen evolution and diminishes the affinity to atrazine binding without affecting the number of binding sites. The content of about four manganeses per functionally competent oxygen evolving complex is not changed by [Cu2+] < 70 μᴍ.Based on these findings it is concluded: i) a temperature dependent equilibrium between an inactive (I) and active (A) state of QA- reoxidation by QB(QB- ) is characterized by standard enthalpies ΔH° of 95 kJ mol-1 and 60 kJ mol-1 and standard entropies ΔS° of 370 kJ K-1 mol-1 and 240 kJ K-1 mol-1 in isolated thylakoids and PS II membrane fragments, respectively, ii) the activation energies of QA- reoxidation by plastoquinone bound to the QB site are about 30 kJ mol-1 (thylakoids) and 40 kJ mol-1 (PS II membrane fragments) in 220 K < T < 300 K, and iii) Cu2+ causes at least a two-fold effect on PS II by modifying the atrazine binding affinity at lower concentrations ( ~ 5 μᴍ) and interference with the redox active tyrosine Yz at slightly higher concentration ( ~ 10 μᴍ) leading to blockage of oxygen evolution.

Photoinactivation of Photosynthetic Electron Transport under Anaerobic and Aerobic Conditions in Isolated Thylakoids of Spinach

1992 ◽  
Vol 47 (1-2) ◽  
pp. 63-68 ◽  
Author(s):  
Rekha Chaturvedi ◽  
M. Singh ◽  
P. V. Sane
Keyword(s):  
Electron Transport ◽  
Photosynthetic Electron Transport ◽  
Oxygen Evolving Complex ◽  
Reaction Centre ◽  
Ps Ii ◽  
Ps I ◽  
S2 State ◽  
The Stability ◽  
Oxygen Evolving ◽  
Spinach Thylakoids

Abstract The effect of exposure to strong white light on photosynthetic electron transport reactions of PS I and PS II were investigated in spinach thylakoids in the absence or presence of oxygen. Irrespective of the conditions used for photoinactivation, the damage to PS II was always much more than to PS I. Photoinactivation was severe under anaerobic conditions compared to that in air for the same duration. This shows that the presence of oxygen is required for prevention of photoinactivation of thylakoids. The susceptibility of water-splitting complex in photoinactivation is indicated by our data from experiments with chloride-deficient chloroplast membranes wherein it was observed that the whole chain electron transport from DPC to MV was much less photoinhibited than that from water. The data from the photoinactivation experiments with the Tris-treated thylakoids indicate another photodam age site at or near reaction centre of PS II. DCMU-protected PS II and oxygen-evolving complex from photoinactivation. DCMU protection can also be interpreted in terms of the stability of the PS II complex when it is in S2 state.

scholarly journals Na2CO3-Responsive Photosynthetic and ROS Scavenging Mechanisms in Chloroplasts of Alkaligrass Revealed by Phosphoproteomics

2019 ◽  
Author(s):  
Jinwei Suo ◽  
Heng Zhang ◽  
Qi Zhao ◽  
Nan Zhang ◽  
Yongxue Zhang ◽  
...  
Keyword(s):  
Quantitative Proteomics ◽  
Energy Homeostasis ◽  
Thermal Dissipation ◽  
Wild Type ◽  
Ros Scavenging ◽  
Fructose Bisphosphate ◽  
Ps Ii ◽  
Ros Homeostasis ◽  
Fructose Bisphosphate Aldolase ◽  
Regulation Of Photosynthesis

Alkali-salinity exerts severe osmotic, ionic and high-pH stresses to plants. To understand the alkali-salinity responsive mechanisms underlying photosynthetic modulation and reactive oxygen species (ROS) homeostasis, physiological and diverse quantitative proteomics analyses of alkaligrass (Puccinellia tenuiflora) under Na2CO3 stress were conducted. In addition, Western blot, real-time PCR, and transgenic techniques were applied to validate the proteomic results and test the functions of the Na2CO3-responsive proteins. A total of 104 and 102 Na2CO3-responsive proteins were identified in leaves and chloroplasts, respectively. In addition, 84 Na2CO3-responsive phosphoproteins were identified, including 56 new phosphorylation sites in 56 phosphoproteins from chloroplasts, which are crucial for the regulation of photosynthesis, ion transport, signal transduction and energy homeostasis. A full-length PtFBA encoding an alkaligrass chloroplastic fructose-bisphosphate aldolase (FBA) was overexpressed in wild-type cells of cyanobacterium Synechocystis sp. Strain PCC 6803, leading to enhanced Na2CO3 tolerance. All these results indicate that thermal dissipation, state transition, cyclic electron transport, photorespiration, repair of photosystem (PS) II, PSI activity, and ROS homeostasis were altered in response to Na2CO3 stress, and they have improved our understanding of the Na2CO3-responsive mechanisms in halophytes.

scholarly journals Untangling the sequence of events during the S2→ S3transition in photosystem II and implications for the water oxidation mechanism

2020 ◽  
Vol 117 (23) ◽  
pp. 12624-12635 ◽  
Author(s):  
Mohamed Ibrahim ◽  
Thomas Fransson ◽  
Ruchira Chatterjee ◽  
Mun Hon Cheah ◽  
Rana Hussein ◽  
...  
Keyword(s):  
Photosystem Ii ◽  
Water Oxidation ◽  
Donor Site ◽  
Oxidation Mechanism ◽  
Oxygenic Photosynthesis ◽  
Acceptor Site ◽  
Oxygen Evolving Complex ◽  
Ps Ii ◽  
Sequence Of Events ◽  
Large Channel

In oxygenic photosynthesis, light-driven oxidation of water to molecular oxygen is carried out by the oxygen-evolving complex (OEC) in photosystem II (PS II). Recently, we reported the room-temperature structures of PS II in the four (semi)stable S-states, S1, S2, S3, and S0, showing that a water molecule is inserted during the S2→ S3transition, as a new bridging O(H)-ligand between Mn1 and Ca. To understand the sequence of events leading to the formation of this last stable intermediate state before O2formation, we recorded diffraction and Mn X-ray emission spectroscopy (XES) data at several time points during the S2→ S3transition. At the electron acceptor site, changes due to the two-electron redox chemistry at the quinones, QAand QB, are observed. At the donor site, tyrosine YZand His190 H-bonded to it move by 50 µs after the second flash, and Glu189 moves away from Ca. This is followed by Mn1 and Mn4 moving apart, and the insertion of OX(H) at the open coordination site of Mn1. This water, possibly a ligand of Ca, could be supplied via a “water wheel”-like arrangement of five waters next to the OEC that is connected by a large channel to the bulk solvent. XES spectra show that Mn oxidation (τ of ∼350 µs) during the S2→ S3transition mirrors the appearance of OXelectron density. This indicates that the oxidation state change and the insertion of water as a bridging atom between Mn1 and Ca are highly correlated.

scholarly journals Interaction Between Induced and Natural Variation at oil yellow1 Delays Reproductive Maturity in Maize

2019 ◽  
Vol 10 (2) ◽  
pp. 797-810
Author(s):  
Rajdeep S. Khangura ◽  
Bala P. Venkata ◽  
Sandeep R. Marla ◽  
Michael V. Mickelbart ◽  
Singha Dhungana ◽  
...  
Keyword(s):  
Flowering Time ◽  
Chlorophyll Content ◽  
Chlorophyll Biosynthesis ◽  
Wild Type ◽  
Reproductive Maturity ◽  
Magnesium Chelatase ◽  
Chlorophyll Contents ◽  
Delayed Flowering ◽  
Mapping Populations ◽  
Expression Polymorphism

We previously demonstrated that maize (Zea mays) locus very oil yellow1 (vey1) encodes a putative cis-regulatory expression polymorphism at the magnesium chelatase subunit I gene (aka oil yellow1) that strongly modifies the chlorophyll content of the semi-dominant Oy1-N1989 mutants. The vey1 allele of Mo17 inbred line reduces chlorophyll content in the mutants leading to reduced photosynthetic output. Oy1-N1989 mutants in B73 reached reproductive maturity four days later than wild-type siblings. Enhancement of Oy1-N1989 by the Mo17 allele at the vey1 QTL delayed maturity further, resulting in detection of a flowering time QTL in two bi-parental mapping populations crossed to Oy1-N1989. The near isogenic lines of B73 harboring the vey1 allele from Mo17 delayed flowering of Oy1-N1989 mutants by twelve days. Just as previously observed for chlorophyll content, vey1 had no effect on reproductive maturity in the absence of the Oy1-N1989 allele. Loss of chlorophyll biosynthesis in Oy1-N1989 mutants and enhancement by vey1 reduced CO2 assimilation. We attempted to separate the effects of photosynthesis on the induction of flowering from a possible impact of chlorophyll metabolites and retrograde signaling by manually reducing leaf area. Removal of leaves, independent of the Oy1-N1989 mutant, delayed flowering but surprisingly reduced chlorophyll contents of emerging leaves. Thus, defoliation did not completely separate the identity of the signal(s) that regulates flowering time from changes in chlorophyll content in the foliage. These findings illustrate the necessity to explore the linkage between metabolism and the mechanisms that connect it to flowering time regulation.

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