14 research outputs found
Role of Serine/Threonine Protein Kinase Stn7 in the Formation of Two Distinct Photosystem I Supercomplexes in Physcomitrium patens
No full textPhosphorylation-dependent formation of photosystem I supercomplexes provides both short- and long-term acclimation of moss photosynthetic apparatus to changing environmental cues.Reversible thylakoid protein phosphorylation provides most flowering plants with dynamic acclimation to short-term changes in environmental light conditions. Here, through generating Serine/Threonine protein kinase 7 (STN7)-depleted mutants in the moss Physcomitrella (Physcomitrium patens), we identified phosphorylation targets of STN7 kinase and their roles in short- and long-term acclimation of the moss to changing light conditions. Biochemical and mass spectrometry analyses revealed STN7-dependent phosphorylation of N-terminal Thr in specific Light-Harvesting Complex II (LHCII) trimer subunits (LHCBM2 and LHCBM4/8) and provided evidence that phospho-LHCBM accumulation is responsible for the assembly of two distinct Photosystem I (PSI) supercomplexes (SCs), both of which are largely absent in STN7-depleted mutants. Besides the canonical state transition complex (PSI-LHCI-LHCII), we isolated the larger moss-specific PSI-Large (PSI-LHCI-LHCB9-LHCII) from stroma-exposed thylakoids. Unlike PSI-LHCI-LHCII, PSI-Large did not demonstrate short-term dynamics for balancing the distribution of excitation energy between PSII and PSI. Instead, PSI-Large contributed to a more stable increase in PSI antenna size in Physcomitrella, except under prolonged high irradiance. Additionally, the STN7-depleted mutants revealed altered light-dependent phosphorylation of a monomeric antenna protein, LHCB6, whose phosphorylation displayed a complex regulation by multiple kinases. Collectively, the unique phosphorylation plasticity and dynamics of Physcomitrella monomeric LHCB6 and trimeric LHCBM isoforms, together with the presence of PSI SCs with different antenna sizes and responsiveness to light changes, reflect the evolutionary position of mosses between green algae and vascular plants, yet with clear moss-specific features emphasizing their adaptation to terrestrial low-light environments
Diversity in phosphorylation of thylakoid membrane proteins in chloroplasts
No full textPhotosynthesis is the most fundamental process for life on Earth. Sunlight is highly variable and fluctuates both in intensity and duration, which induces short and longterm responses in photosynthetic organisms. Photosynthetic organisms have evolved several processes to cope with environmental stresses, including light fluctuations. Many thylakoid properties and functions are regulated by diverse protein phosphorylations, ranging from thylakoid ultrastructural changes and the optimization of excitation energy between the two photosystems via Lightharvesting complexes (LHCs) to signaling mechanisms for long-term regulation, maintaining proteostasis, and thereby ultimately regulating photosynthesis via photoprotection mechanisms.
My PhD research is divided into three major projects. The first one gives evolutionary insights into the two main thylakoid kinases, STN7 and STN8 in Physcomitrium patens (previously Physcomitrella patens), and their target proteins. Physcomitrium patens differs from angiosperms in their photoprotection strategy via LHCII phosphorylations (LHCB6 and LHCBM) and in formation of a Photosystem (PS)I-supercomplex, PSI-large, depending on LHCBM phosphorylation.
The second project focuses on angiosperm model species Arabidopsis thaliana and deals with protein phosphorylation-related changes in thylakoid architecture. The study reveals that the phosphorylation dynamics of LHCII and CURT1B respond co-operatively to fluctuating light intensities. The findings also suggest that CURT1B phosphorylation contributes to the fine-tuning of thylakoid membrane structure and function in response to light conditions.
The third project delves into the potential association between calcium signaling and induction of photoprotective mechanisms, by providing a novel screening tool to identify calcium-dependent chloroplast proteins. Calcium-transient dependent phosphorylation of essential proteins involved in the repair of PSII, including THF1, HCF136, and FTSH protease were disclosed. Additionally, the study proposes a potential link of calcium in PSI-Fd-FNR interaction. Moreover, this study not only identifies the new phosphorylation targets but also presents opportunities for exploring the intricate interplay between calcium signaling and protein phosphorylation processes. Taken together, my PhD research helps in understanding the regulation of photosynthesis, provides new tools for photosynthesis research and will thereby contribute to engineering photosynthetically resilient organisms to cope with changing environmental conditions for improving the production of food, feed and renewable energy.----
Fotosynteesi ylläpitää elämää maapallolla muuttamalla auringon valoenergiaa kemialliseksi energiaksi. Auringonvalo vaihtelee sekä voimakkuudeltaan että kestoltaan, mikä saa aikaan lyhyt- ja pitkäaikaisia vasteita fotosynteettisissä organismeissa. Fotosynteettiset organismit ovat kehittäneet useita prosesseja selviytyäkseen ympäristönstresseistä, mukaan lukien voimakkaat valon vaihtelut. Kasvien fotosynteesi tapahtuu viherhiukkasten sisäisessä kalvosysteemissä, tylakoideissa, joiden ominaisuuksia ja toimintoja säätelevät erilaiset proteiinien fosforylaatiot. Valohaaviproteiinien (LHCII) fosforylaatio muuttaa tylakoidin hienorakennetta ja optimoi viritysenergian jakautumista kahden valoreaktion (PSII ja PSI) välillä, mutta vaikuttaa myös signaalimekanismien kautta proteostaasin ylläpitämiseen ja siten viime kädessä fotosynteesin pitkänajan säätelyyn.
Tohtoritutkimukseni on jaettu kolmeen osaprojektiin. Ensimmäinen pureutuu kahdessa tärkeimmässä tylakoidikinaasissa (STN7 ja STN8) ja niiden kohdeproteiineissa evoluution aikana tapahtuneisiin muutoksiin. Tutkimus osoitti sammalen, evolutiivisesti vanhimman maakasvin, eroavan valosuojausstrategiassaan siemenkasveista, ja muokkaavan LHCB6 ja LHCBM proteiinien fosforylaatioiden ja PSI-superkompleksien muodostumisen kautta viritysenergian jakautumista PSII:n ja PSI:n välillä.
Toinen osaprojekti käsittelee siemenkasvien malliorganismin, lituruohon (Arabidopsis thaliana), tylakoidiproteiinien fosforylaation aiheuttamia muutoksia tylakoidiverkoston hienorakenteessa, ja paljastaa LHCII:n ja CURT1B:n fosforylaatiodynamiikan yhteistyön vaikuttavan rakenteen ja toiminnan väliseen hienosäätöön, toimien vasteena valo-olosuhteiden muutoksille.
Kolmannessa osaprojektissa tarkastellaan mahdollista kalsium-signaloinnin ja kasvin proteiinifosforylaatioon perustuvan valosuojausmekanismin välistä yhteyttä, käyttämällä hyväksi seulontaan kehitettyä uutta työkalua. Tutkimuksessa kuvattiin PSII:n korjaamiseen välttämättä tarvittavien proteiinien (THF1, HCF136 ja FTSHproteaasi) kalsiumista riippuvainen fosforylaatio. Lisäksi tutkimustulokset viittaavat kalsiumin toimintaan PSI-Fd-FNR vuorovaikutuksessa sekä erittäin monimutkaiseen vuorovaikutukseen kalsium-signaloinnin ja proteiinien fosforylaatioprosessien välillä.
Yhteenvetona totean, että väitöskirjatutkimukseni auttaa ymmärtämään fotosynteesin säätelyä, tarjoaa uusia työkaluja fotosynteesin tutkimukseen ja myötävaikuttaa siten uusien, fotosynteettisesti kestävien ja tehokkaiden organismien suunnitteluun ja tuottamiseen. Tämä puolestaan edesauttaa selviytymistämme muuttuvissa ympäristöolosuhteissa ruoan, rehun ja uusiutuvan energian tuotannon parantamiseksi.ei tietoa saavutettavuudest
Higher order photoprotection mutants reveal the importance of ΔpH-dependent photosynthesis-control in preventing light induced damage to both photosystem II and photosystem I
No full textAlthough light is essential for photosynthesis, when in excess, it may damage the photosynthetic
apparatus, leading to a phenomenon known as photoinhibition. Photoinhibition was thought as a
light-induced damage to photosystem II; however, it is now clear that even photosystem I may become
very vulnerable to light. One main characteristic of light induced damage to photosystem II (PSII) is
the increased turnover of the reaction center protein, D1: when rate of degradation exceeds the rate of
synthesis, loss of PSII activity is observed. With respect to photosystem I (PSI), an excess of electrons,
instead of an excess of light, may be very dangerous. Plants possess a number of mechanisms able
to prevent, or limit, such damages by safe thermal dissipation of light energy (non-photochemical
quenching, NPQ), slowing-down of electron transfer through the intersystem transport chain
(photosynthesis-control, PSC) in co-operation with the Proton Gradient Regulation (PGR) proteins,
PGR5 and PGRL1, collectively called as short-term photoprotection mechanisms, and the redistribution
of light between photosystems, called state transitions (responsible of fluorescence quenching at PSII,
qT), is superimposed to these short term photoprotective mechanisms. In this manuscript we have
generated a number of higher order mutants by crossing genotypes carrying defects in each of the
short-term photoprotection mechanisms, with the final aim to obtain a direct comparison of their role
and efficiency in photoprotection. We found that mutants carrying a defect in the ΔpH-dependent
photosynthesis-control are characterized by photoinhibition of both photosystems, irrespectively of
whether PSBS-dependent NPQ or state transitions defects were present or not in the same individual,
demonstrating the primary role of PSC in photoprotection. Moreover, mutants with a limited capability
to develop a strong PSBS-dependent NPQ, were characterized by a high turnover of the D1 protein and
high values of Y(NO), which might reflect energy quenching processes occurring within the PSII reaction
center
Investigating the potential of multiwalled carbon nanotubes based zinc nanocomposite as a recognition interface towards plant pathogen detection
No full textThe emergence of nanotechnology has opened new horizons for constructing efficient recognition interfaces. This is the first report where the potential of a multiwalled carbon nanotube based zinc nanocomposite (MWCNTs-Zn NPs) investigated for the detection of an agricultural pathogen i.e. Chili leaf curl betasatellite (ChLCB). Atomic force microscope analyses revealed the presence of multiwalled carbon nanotubes (MWCNTs) having a diameter of 50-100 nm with zinc nanoparticles (Zn-NPs) of 25-500 nm. In this system, these bunches of Zn-NPs anchored along the whole lengths of MWCNTs were used for the immobilization of probe DNA strands. The electrochemical performance of DNA biosensor was assessed in the absence and presence of the complementary DNA during cyclic and differential pulse voltammetry scans. Target binding events occurring on the interface surface patterned with single-stranded DNA was quantitatively translated into electrochemical signals due to hybridization process. In the presence of complementary target DNA, as the result of duplex formation, there was a decrease in the peak current from 1.89 x 10(-04) to 5.84 x 10(-05) A. The specificity of this electrochemical DNA biosensor was found to be three times as compared to non-complementary DNA. This material structuring technique can be extended to design interfaces for the recognition of the other plant viruses and biomolecules.International Foundation for Science (IFS), Sweden; Organization of Islamic Cooperation's (OIC) Standing Committee on Scientific and Technological Cooperation (COMSTECH) [E-5659]SCI(E)ARTICLE130-13624
The Role of Phosphorylation Dynamics of CURVATURE THYLAKOID 1B in Plant Thylakoid Membranes
No full textThylakoid membranes in land plant chloroplasts are organized into appressed and nonappressed membranes, which contribute to the control of energy distribution between the two photosystems (PSI and PSII) from the associated light-harvesting complexes (LHCs). Under fluctuating light conditions, fast reversible phosphorylation of the N-terminal thylakoid protein domains and changes in electrostatic forces induce modifications in thylakoid organization. To gain insight into the role and dynamics of thylakoid protein phosphorylation, we used targeted proteomics to quantify amounts of the structural proteins CURVATURE THYLAKOID1 (CURT1), including the levels of CURT1B N terminus phosphorylation and acetylation, after short-term fluctuating light treatments of Arabidopsis (Arabidopsis thaliana). The CURT1B protein was localized to a specific curvature domain separated from the margin domain, and specifically depleted of chlorophyll-binding protein complexes. The acetylation and phosphorylation of the CURT1B N terminus were mutually exclusive. The level of CURT1B phosphorylation, but not of acetylation, increased upon light shifts that also led to an increase in PSII core protein phosphorylation. These dynamics were largely absent in the knockout mutant of PSII core protein kinase SER/THR PROTEIN KINASE8 (STN8). Moreover, in mutants impaired in interaction between phosphorylated LHCII and PSI, the phosphorylation dynamics of CURT1B and the amount of the other CURT1 proteins were misregulated, indicating a functional interaction between CURT1B and PSI-LHCII complexes in grana margins. The complex relationships between phosphorylation of PSII, LHCII, and CURT1B support the dynamics of thylakoid protein complexes that are crucial in the optimization of photosynthesis under fluctuating light intensities.</p
Optimizing the phosphorus use in cotton by using CSM-CROPGRO-cotton model for semi-arid climate of Vehari-Punjab, Pakistan
No full textRahman, Muhammad Habib ur/0000-0002-2823-9959; Jabran, Khawar/0000-0001-8512-3330; Hakeem, Khalid Rehman/0000-0001-7824-4695; Amin, Asad/0000-0003-2242-8377; Ata-Ul-Karim, Syed Tahir/0000-0001-5233-4502; Jatoi, Ghulam Hussain/0000-0002-7266-1567; Rehmani, M.I.A./0000-0001-7922-1233; Bajwa, Ali/0000-0002-7171-3118; Nadeem, Muhammad/0000-0002-7426-1196; Ata-Ul-Karim, Syed Tahir/0000-0001-5233-4502; Ameen, Asif/0000-0002-3982-7000; Islam, Faisal/0000-0002-1471-1570WOS: 000397013000067PubMed: 28054268Crop nutrient management is an essential component of any cropping system. With increasing concerns over environmental protection, improvement in fertilizer use efficiencies has become a prime goal in global agriculture system. Phosphorus (P) is one of the most important nutrients, and strategies are required to optimize its use in important arable crops like cotton (Gossypium hirsutum L.) that has great significance. Sustainable P use in crop production could significantly avoid environmental hazards resulting from over-P fertilization. Crop growth modeling has emerged as an effective tool to assess and predict the optimal nutrient requirements for different crops. In present study, Decision Support System for Agro-technology Transfer (DSSAT) sub-model CSM-CROPGRO- Cotton-P was evaluated to estimate the observed and simulated P use in two cotton cultivars grown at three P application rates under the semi-arid climate of southern Punjab, Pakistan. The results revealed that both the cultivars performed best at medium rate of P application (57 kg ha(-1)) in terms of days to anthesis, days to maturity, seed cotton yield, total dry matter production, and harvest index during 2013 and 2014. Cultivar FH-142 performed better than MNH-886 in terms of different yield components. There was a good agreement between observed and simulated days to anthesis (0 to 1 day), days to maturity (0 to 2 days), seed cotton yield, total dry matter, and harvest index with an error of -4.4 to 15%, 12-7.5%, and 13-9.5% in MNH-886 and for FH-142, 4-16%, 19-11%, and 16-8.3% for growing years 2013 and 2014, respectively. CROPGRO-Cotton-P would be a useful tool to forecast cotton yield under different levels of P in cotton production system of the semi-arid climate of Southern Punjab.Government of Australia [4915_2015]; Higher Education Commission (HEC) of PakistanHigher Education Commission of PakistanThe first author is grateful to the International Global Change Institute (IGCI) Hamilton, New Zealand, for providing the software (SimCLIM2013) and the required climatic dataset for future projections with for southern Punjab, Pakistan. The first author is thankful to Prof. Dr. Gerrit Hoogenboom (Ex-Director, AgWeatherNet, Washington State University, USA; Currently: University of Florida-USA), for his technical guidance and support during the entire period of study and modeling work. Furthermore, first author is highly thankful from NASA for weather data of respective years (which was obtained from website http://power.larc.nasa.gov/cgi-bin/cgiwrap). The corresponding author (Wajid NASIM) is highly thankful to Government of Australia, for Endeavor Research Award/Fellowship (No. 4915_2015) to The Commonwealth Scientific and Industrial Research Organization (CSIRO), Sustainable Agriculture, National Research Flagship, Toowoomba-QLD 4350, Australia. Furthermore, co-authors (Wajid NASIM and Shakeel AHMAD) are highly thankful for Higher Education Commission (HEC) of Pakistan for partial funding
Specific thylakoid protein phosphorylations are prerequisites for overwintering of Norway spruce (Picea abies) photosynthesis
No full textCoping of evergreen conifers in boreal forests with freezing temperatures on bright winter days puts the photosynthetic machinery in great risk of oxidative damage. To survive harsh winter conditions, conifers have evolved a unique but poorly characterized photoprotection mechanism, a sustained form of nonphotochemical quenching (sustained NPQ). Here we focused on functional properties and underlying molecular mechanisms related to the development of sustained NPQ in Norway spruce (Picea abies). Data were collected during 4 consecutive years (2016 to 2019) from trees growing in sun and shade habitats. When day temperatures dropped below -4 degrees C, the specific N-terminally triply phosphorylated LHCB1 isoform (3p-LHCII) and phosphorylated PSBS (p-PSBS) could be detected in the thylakoid membrane. Development of sustained NPQ coincided with the highest level of 3p-LHCII and p-PSBS, occurring after prolonged coincidence of bright winter days and temperatures close to -10 degrees C. Artificial induction of both the sustained NPQ and recovery from naturally induced sustained NPQ provided information on differential dynamics and light-dependence of 3p-LHCII and p-PSBS accumulation as prerequisites for sustained NPQ. Data obtained collectively suggest three components related to sustained NPQ in spruce: 1) Freezing temperatures induce 3p-LHCII accumulation independently of light, which is suggested to initiate destacking of appressed thylakoid membranes due to increased electrostatic repulsion of adjacent membranes; 2) p-PSBS accumulation is both light -and temperature-dependent and closely linked to the initiation of sustained NPQ, which 3) in concert with PSII photoinhibition, is suggested to trigger sustained NPQ in spruce
Higher order photoprotection mutants reveal the importance of ΔpH-dependent photosynthesis-control in preventing light induced damage to both photosystem II and photosystem I
No full textAlthough light is essential for photosynthesis, when in excess, it may
damage the photosynthetic apparatus, leading to a phenomenon known as
photoinhibition. Photoinhibition was thought as a light-induced damage
to photosystem II; however, it is now clear that even photosystem I may
become very vulnerable to light. One main characteristic of light
induced damage to photosystem II (PSII) is the increased turnover of the
reaction center protein, D1: when rate of degradation exceeds the rate
of synthesis, loss of PSII activity is observed. With respect to
photosystem I (PSI), an excess of electrons, instead of an excess of
light, may be very dangerous. Plants possess a number of mechanisms able
to prevent, or limit, such damages by safe thermal dissipation of light
energy (non-photochemical quenching, NPQ), slowing-down of electron
transfer through the intersystem transport chain
(photosynthesis-control, PSC) in co-operation with the Proton Gradient
Regulation (PGR) proteins, PGR5 and PGRL1, collectively called as
short-term photoprotection mechanisms, and the redistribution of light
between photosystems, called state transitions (responsible of
fluorescence quenching at PSII, qT), is superimposed to these short term
photoprotective mechanisms. In this manuscript we have generated a
number of higher order mutants by crossing genotypes carrying defects in
each of the short-term photoprotection mechanisms, with the final aim
to obtain a direct comparison of their role and efficiency in
photoprotection. We found that mutants carrying a defect in the
ΔpH-dependent photosynthesis-control are characterized by
photoinhibition of both photosystems, irrespectively of whether
PSBS-dependent NPQ or state transitions defects were present or not in
the same individual, demonstrating the primary role of PSC in
photoprotection. Moreover, mutants with a limited capability to develop a
strong PSBS-dependent NPQ, were characterized by a high turnover of the
D1 protein and high values of Y(NO), which might reflect energy
quenching processes occurring within the PSII reaction center.</p
Author Correction: Diagnosis, grading and management of toxicities from immunotherapies in children, adolescents and young adults with cancer
No full textCorrection to: Nature Reviews Clinical Oncology https://doi.org/10.1038/s41571-021-00474-4, published online 19 February 2021.
In the original version of this Consensus Statement, the name of the author Christine N. Duncan was incorrectly written as Christine N. Duncun. In addition, Fig. 1 contained errors regarding the criteria to grade cytokine-release syndrome (CRS). “Hypotension not requiring vasopressors” has now been corrected to “hypotension requiring one vasopressor ± vasopressin” for grade 3 CRS and “hypotension requiring multiple vasopressors, not including vasopressin” for grade 4 CRS. The affiliations and Fig. 1 have been corrected in the HTML and PDF versions of the manuscript
Correction: Zaman et al. Synthesis and Evaluation of Thiol-Conjugated Poloxamer and Its Pharmaceutical Applications. <em>Pharmaceutics</em> 2021, <em>13</em>, 693
No full textIn the original publication, there was a mistake in one author name, Mohammed Alasmari should be Mohammed S [...
