Role In Regulation Of Photosynthesis Research Articles

Genome-wide identification of the geranylgeranyl pyrophosphate synthase (GGPS) gene family involved in chlorophyll synthesis in cotton

BackgroundGeranylgeranyl pyrophosphate synthase (GGPS) is a structural enzyme of the terpene biosynthesis pathway that is involved in regulating plant photosynthesis, growth and development, but this gene family has not been systematically studied in cotton.ResultsIn the current research, genome-wide identification was performed, and a total of 75 GGPS family members were found in four cotton species, Gossypium hirsutum, Gossypium barbadense, Gossypium arboreum and Gossypium raimondii. The GGPS genes were divided into three subgroups by evolutionary analysis. Subcellular localization prediction showed that they were mainly located in chloroplasts and plastids. The closely related GGPS contains a similar gene structure and conserved motif, but some genes are quite different, resulting in functional differentiation. Chromosome location analysis, collinearity and selection pressure analysis showed that many fragment duplication events occurred in GGPS genes. Three-dimensional structure analysis and conservative sequence analysis showed that the members of the GGPS family contained a large number of α-helices and random crimps, and all contained two aspartic acid-rich domains, DDxxxxD and DDxxD (x is an arbitrary amino acid), suggesting its key role in function. Cis-regulatory element analysis showed that cotton GGPS may be involved in light response, abiotic stress and other processes. A GGPS gene was silenced successfully by virus-induced gene silencing (VIGS), and it was found that the chlorophyll content in cotton leaves decreased significantly, suggesting that the gene plays an important role in plant photosynthesis.ConclusionsIn total, 75 genes were identified in four Gossypium species by a series of bioinformatics analysis. Gene silencing from GGPS members of G. hirsutum revealed that GGPS plays an important regulatory role in photosynthesis. This study provides a theoretical basis for the biological function of GGPS in cotton growth and development.

Disequilibrium evolution of the Fructose-1,6-bisphosphatase gene family leads to their functional biodiversity in Gossypium species

BackgroundFructose-1,6-bisphosphatase (FBP) is a key enzyme in the plant sucrose synthesis pathway, in the Calvin cycle, and plays an important role in photosynthesis regulation in green plants. However, no systemic analysis of FBPs has been reported in Gossypium species.ResultsA total of 41 FBP genes from four Gossypium species were identified and analyzed. These FBP genes were sorted into two groups and seven subgroups. Results revealed that FBP family genes were under purifying selection pressure that rendered FBP family members as being conserved evolutionarily, and there was no tandem or fragmental DNA duplication in FBP family genes. Collinearity analysis revealed that a FBP gene was located in a translocated DNA fragment and the whole FBP gene family was under disequilibrium evolution that led to a faster evolutionary progress of the members in G. barbadense and in At subgenome than those in other Gossypium species and in the Dt subgenome, respectively, in this study. Through RNA-seq analyses and qRT-PCR verification, different FBP genes had diversified biological functions in cotton fiber development (two genes in 0 DPA and 1DPA ovules and four genes in 20–25 DPA fibers), in plant responses to Verticillium wilt onset (two genes) and to salt stress (eight genes).ConclusionThe FBP gene family displayed a disequilibrium evolution pattern in Gossypium species, which led to diversified functions affecting not only fiber development, but also responses to Verticillium wilt and salt stress. All of these findings provide the foundation for further study of the function of FBP genes in cotton fiber development and in environmental adaptability.

In vivo evidence for a regulatory role of phosphorylation of Arabidopsis Rubisco activase at the Thr78 site

Arabidopsis Rubisco activase (Rca) is phosphorylated at threonine-78 (Thr78) in low light and in the dark, suggesting a potential regulatory role in photosynthesis, but this has not been directly tested. To do so, we transformed an rca-knockdown mutant largely lacking redox regulation with wild-type Rca-β or Rca-β with Thr78-to-Ala (T78A) or Thr78-to-Ser (T78S) site-directed mutations. Interestingly, the T78S mutant was hyperphosphorylated at the Ser78 site relative to Thr78 of the Rca-β wild-type control, as evidenced by immunoblotting with custom antibodies and quantitative mass spectrometry. Moreover, plants expressing the T78S mutation had reduced photosynthesis and quantum efficiency of photosystem II (ϕPSII) and reduced growth relative to control plants expressing wild-type Rca-β under all conditions tested. Gene expression was also altered in a manner consistent with reduced growth. In contrast, plants expressing Rca-β with the phospho-null T78A mutation had faster photosynthetic induction kinetics and increased ϕPSII relative to Rca-β controls. While expression of the wild-type Rca-β or the T78A mutant fully rescued the slow-growth phenotype of the rca-knockdown mutant grown in a square-wave light regime, the T78A mutants grew faster than the Rca-β control plants at low light (30 µmol photons m-2 s-1) and in a fluctuating low-light/high-light environment. Collectively, these results suggest that phosphorylation of Thr78 (or Ser78 in the T78S mutant) plays a negative regulatory role in vivo and provides an explanation for the absence of Ser at position 78 in terrestrial plant species.

A novel ethylene responsive factor CitERF13 plays a role in photosynthesis regulation

Ethylene responsive factors (ERFs) act as critical downstream components of the ethylene signalling pathway in regulating plant development and stress responses. However little is known about its role in regulation of photosynthesis. Here, we identified an ethylene-inducible ERF gene in citrus, CitERF13. Transient over-expression of CitERF13 in N. tabacum leaves, resulted in a significant decrease in net photosynthetic rate. Closer examination of photosynthetic activity of PSII and PSI indicated that CitERF13 overexpression led to declines of Fv/Fm, Y(II) and Y(I). However, change in NPQ was less pronounced. CitERF13 overexpression also significantly reduced Vc,max, Jmax and AQY, indicating inhibition of the Calvin cycle. The expression of photosynthesis-related genes was suppressed to a variable extent in leaf blades transiently over-expressing CitERF13. CitERF13 transient overexpression in tobacco or citrus both resulted in a decline of Chlorophyll content and CitERF13 overexpressing tobacco leaf disc was more susceptible to chlorosis in response to MV-mediated oxidative stress. The results suggest that CitERF13 is potentially involved in suppressing photosynthesis through multiple pathways, for instance, inhibiting photochemical activity of photosynthesis, CO2 carboxylation capacity and chlorophyll metabolism.

Leaf nitrogen spectral reflectance model of winter wheat (Triticum aestivum) based on PROSPECT: simulation and inversion

Through its association with proteins and plant pigments, leaf nitrogen (N) plays an important regulatory role in photosynthesis, leaf respiration, and net primary production. However, the traditional methods of measurement leaf N are rooted in sample-based spectroscopy in laboratory. There is a big challenge of deriving leaf N from the nondestructive field-measured leaf spectra. In this study, the original PROSPECT model was extended by replacing the absorption coefficient of chlorophyll in the original PROSPECT model with an equivalent N absorption coefficient to develop a nitrogen-based PROSPECT model (N-PROSPECT). N-PROSPECT was evaluated by comparing the model-simulated reflectance values with the measured leaf reflectance values. The validated results show that the correlation coefficient (R) was 0.98 for the wavelengths of 400 to 2500 nm. Finally, N-PROSPECT was used to simulate leaf reflectance using different combinations of input parameters, and partial least squares regression (PLSR) was used to establish the relationship between the N-PROSPECT simulated reflectance and the corresponding leaf nitrogen density (LND). The inverse of the PLSR-based N-PROSPECT model was used to retrieve LND from the measured reflectance with a relatively high accuracy (R2=0.77, RMSE=22.15 μg cm−2). This result demonstrates that the N-PROSPECT model established in this study can accurately simulate nitrogen spectral contributions and retrieve LND.

Conserved Epigenetic Mechanisms Could Play a Key Role in Regulation of Photosynthesis and Development-Related Genes during Needle Development of Pinus radiata.

Needle maturation is a complex process that involves cell growth, differentiation and tissue remodelling towards the acquisition of full physiological competence. Leaf induction mechanisms are well known; however, those underlying the acquisition of physiological competence are still poorly understood, especially in conifers. We studied the specific epigenetic regulation of genes defining organ function (PrRBCS and PrRBCA) and competence and stress response (PrCSDP2 and PrSHMT4) during three stages of needle development and one de-differentiated control. Gene-specific changes in DNA methylation and histone were analysed by bisulfite sequencing and chromatin immunoprecipitation (ChIP). The expression of PrRBCA and PrRBCS increased during needle maturation and was associated with the progressive loss of H3K9me3, H3K27me3 and the increase in AcH4. The maturation-related silencing of PrSHMT4 was correlated with increased H3K9me3 levels, and the repression of PrCSDP2, to the interplay between AcH4, H3K27me3, H3K9me3 and specific DNA methylation. The employ of HAT and HDAC inhibitors led to a further determination of the role of histone acetylation in the regulation of our target genes. The integration of these results with high-throughput analyses in Arabidopsis thaliana and Populus trichocarpa suggests that the specific epigenetic mechanisms that regulate photosynthetic genes are conserved between the analysed species.

Carotenoid-chlorophyll coupling and fluorescence quenching in aggregated minor PSII proteins CP24 and CP29.

It is known that aggregation of isolated light-harvesting complex II (LHCII) in solution results in high fluorescence quenching, reduced chlorophyll fluorescence lifetime, and increased electronic coupling of carotenoid (Car) S1 and chlorophyll (Chl) Qy states, as determined by two-photon studies. It has been suggested that this behavior of aggregated LHCII mimics aspects of non-photochemical quenching processes of higher plants and algae. However, several studies proposed that the minor photosystem II proteins CP24 and CP29 also play a significant role in regulation of photosynthesis. Therefore, we use a simple protocol that allows gradual aggregation also of CP24 and CP29. Similarly, as observed for LHCII, aggregation of CP24 and CP29 also leads to increasing fluorescence quenching and increasing electronic Car S1-Chl Qy coupling. Furthermore, a direct comparison of the three proteins revealed a significant higher electronic coupling in the two minor proteins already in the absence of any aggregation. These differences become even more prominent upon aggregation. A red-shift of the Qy absorption band known from LHCII aggregation was also observed for CP29 but not for CP24. We discuss possible implications of these results for the role of CP24 and CP29 as potential valves for excess excitation energy in the regulation of photosynthetic light harvesting.

Global analysis of photosynthesis transcriptional regulatory networks.

Photosynthesis is a crucial biological process that depends on the interplay of many components. This work analyzed the gene targets for 4 transcription factors: FnrL, PrrA, CrpK and MppG (RSP_2888), which are known or predicted to control photosynthesis in Rhodobacter sphaeroides. Chromatin immunoprecipitation followed by high-throughput sequencing (ChIP-seq) identified 52 operons under direct control of FnrL, illustrating its regulatory role in photosynthesis, iron homeostasis, nitrogen metabolism and regulation of sRNA synthesis. Using global gene expression analysis combined with ChIP-seq, we mapped the regulons of PrrA, CrpK and MppG. PrrA regulates ∼34 operons encoding mainly photosynthesis and electron transport functions, while CrpK, a previously uncharacterized Crp-family protein, regulates genes involved in photosynthesis and maintenance of iron homeostasis. Furthermore, CrpK and FnrL share similar DNA binding determinants, possibly explaining our observation of the ability of CrpK to partially compensate for the growth defects of a ΔFnrL mutant. We show that the Rrf2 family protein, MppG, plays an important role in photopigment biosynthesis, as part of an incoherent feed-forward loop with PrrA. Our results reveal a previously unrealized, high degree of combinatorial regulation of photosynthetic genes and significant cross-talk between their transcriptional regulators, while illustrating previously unidentified links between photosynthesis and the maintenance of iron homeostasis.

Comparative roles of brassinosteroids and polyamines in salt stress tolerance

Salt stress is among the major abiotic stresses that adversely affect the global crop production and its adverse impacts are getting more serious in the regions where saline water is used for irrigation. It induces reactive oxygen species, alters the activity of antioxidant system and adversely affects the process of photosynthesis. Various strategies have been employed to mitigate the deleterious effects of salt stress. Presently, the recommended strategies to overcome the adverse effects of salt stress include the use of tolerant cultivars, ameliorative water management and diverse cultural practices. However, none of these approaches have been found to be fully effective under salt stress conditions. An alternative and technically simpler approach to induce salt stress tolerance is the exogenous application of plant growth regulators (PGRs). This technique has gained significant importance during the past decade. PGRs have been implicated to regulate a wide range of metabolic and physiological activities in plants, ranging from cell division and organogenesis to protection against biotic and abiotic stresses. One of the important factors for enhanced plant productivity by PGRs is their efficiency to overcome the salt-induced stress conditions. Recent findings on the effects of brassinosteroids and polyamines on the salt stress tolerance of crops open new avenues to address the salinity problems. This review enlightens the role of brassinosteroids and polyamines in different plant processes like their role in regulation of photosynthesis, antioxidant systems and other related aspects, thereby improving overall performance of plants.

Accumulation of End Products in Source Leaves Affects Photosynthetic Rate in Peach via Alteration of Stomatal Conductance and Photosynthetic Efficiency

In ‘Beijing 24’ peach [Prunus persica (L.) Batch] trees, a series of source leaves with differing levels of end products were created by retaining fruit (“+fruit”), removing fruit (“−fruit”), or reducing the light period. To alter the light period, leaves were covered with a bag made of brown inner paper and outer silver paper, which was then removed at different times the next day. The highest level of end products were obtained by fruit removal, while reducing the light period resulted in a lower level than “+fruit.” Net photosynthetic rate (Pn) and stomatal conductance (gs) decreased, but leaf temperatures (Tleaf) increased, following an increase in end product levels in leaves. After the “−fruit” treatment, reduced Pn was correlated with lower gs, and Tleaf increase was concomitant with decreases in maximal quantum yield of photosystem II (Fv/Fm), actual photochemical efficiency of photosystem II (ΦPSII), and photochemical quenching, and with an increase in nonphotochemical quenching. However, there were no significant differences in chlorophyll fluorescence between “+fruit” and the two treatments reducing the light period. The ΦPSII decreased following an increase in foliar sorbitol level, and it linearly decreased as sucrose and starch increased. Although fruit removal resulted in a significant accumulation of sucrose, sorbitol, and starch in leaves throughout the day, the extractable activities of several important enzymes involved in carbohydrate leaf storage and translocation did not decrease. Therefore, instead of feedback regulation by the accumulation of end products in source leaves, a high Tleaf induced by decreased stomatal aperture may play a key role in regulation of photosynthesis by limiting the photochemical efficiency of the PSII reaction centers under high levels of the end products in peach leaves.

α-Tocopherol Plays a Role in Photosynthesis and Macronutrient Homeostasis of the Cyanobacterium Synechocystis sp. PCC 6803 That Is Independent of Its Antioxidant Function

alpha-Tocopherol is synthesized exclusively in oxygenic phototrophs and is known to function as a lipid-soluble antioxidant. Here, we report that alpha-tocopherol also has a novel function independent of its antioxidant properties in the cyanobacterium Synechocystis sp. PCC 6803. The photoautotrophic growth rates of wild type and mutants impaired in alpha-tocopherol biosynthesis are identical, but the mutants exhibit elevated photosynthetic activities and glycogen levels. When grown photomixotrophically with glucose (Glc), however, these mutants cease growth within 24 h and exhibit a global macronutrient starvation response associated with nitrogen, sulfur, and carbon, as shown by decreased phycobiliprotein content (35% of the wild-type level) and accumulation of the nblA1-nblA2, sbpA, sigB, sigE, and sigH transcripts. Photosystem II activity and carboxysome synthesis are lost in the tocopherol mutants within 24 h of photomixotrophic growth, and the abundance of carboxysome gene (rbcL, ccmK1, ccmL) and ndhF4 transcripts decreases to undetectable levels. These results suggest that alpha-tocopherol plays an important role in optimizing photosynthetic activity and macronutrient homeostasis in Synechocystis sp. PCC 6803. Several lines of evidence indicate that increased oxidative stress in the tocopherol mutants is unlikely to be the underlying cause of photosystem II inactivation and Glc-induced lethality. Interestingly, insertional inactivation of the pmgA gene, which encodes a putative serine-threonine kinase similar to RsbW and RsbT in Bacillus subtilis, results in a similar increase in glycogen and Glc-induced lethality. Based on these results, we propose that alpha-tocopherol plays a nonantioxidant regulatory role in photosynthesis and macronutrient homeostasis through a signal transduction pathway that also involves PmgA.

Consequences of LHC II deficiency for photosynthetic regulation in chlorina mutants of barley

The light-harvesting chlorophyll a/b proteins associated with PS II (LHC II) are often considered to have a regulatory role in photosynthesis. The photosynthetic responses of four chlorina mutants of barley, which are deficient in LHC II to varying degrees, are examined to evaluate whether LHC II plays a regulatory role in photosynthesis. The efficiencies of light use for PS I and PS II photochemistry and for CO2 assimilation in leaves of the mutants were monitored simultaneously over a wide range of photon flux densities of white light in the presence and absence of supplementary red light. It is demonstrated that the depletions of LHC II in these mutants results in a severe imbalance in the relative rates of excitation of PS I and PS II in favour of PS I, which cannot be alleviated by preferential excitation of PS II. Analyses of xanthophyll cycle pigments and fluorescence quenching in leaves of the mutants indicated that the major LHC II components are not required to facilitate the light-induced quenching associated with zeaxanthin formation. It is concluded that LHC II is important to balance the distribution of excitation energy between PS I and PS II populations over a wide range of photon flux densities. It appears that LHC II may also be important in determining the quantum efficiency of PS II photochemistry by reducing the rate of quenching of excitation energy in the PS II primary antennae.

The Ferredoxin/Thioredoxin System: A Key Element in the Regulatory Function of Light in Photosynthesis

In addition to its well-established function in supplying the energy for carbon dioxide assimilation, light plays a regulatory role in photosynthesis. The ferredoxin/thioredoxin system is a major mechanism whereby light functions in this capacity. Here, light absorbed by chlorophyll is converted via ferredoxin into a reductant messenger, reduced thioredoxin, that interacts with key target enzymes, thereby changing their catalytic activities. In this way, the green plant achieves maximum efficiency of its photosynthetic (light) and heterotrophic (dark) capabilities.

Evidence that calmodulin is in the chloroplast of peas and serves a regulatory role in photosynthesis.

phenothiazine drugs in a Ca2+-dependent manner, is inhibited by phenothiazine drugs, is heat stable, and has other molecular properties similar to calmodulin. To test the hypothesis that the Ca”-calmodulin-activated NAD kinase catalyzes the light-induced conversion of NAD to NADP in chloroplasts, calmodulin-binding drugs were used. These drugs inhibited the lightinduced NAD to NADP conversion at concentrations near those required to inhibit calmodulin, and these results were thus consistent with the hypothesis. These same drugs inhibit photosynthetic oxygen evolution while chlorpromazine sulfoxide, which is ineffective toward calmodulin, does not. These results were consistent with a role for calmodulin in the regulation of NAD kinase and photosynthesis.

Photosynthetic electron transport by Zwittergent-extracted chloroplasts requires solubilized plastocyanin

Evidence from numerous laboratories had demonstrated that light plays a regulatory role in photosynthesis through the modulation of key enzymes [1-3]. One system that has been proposed to account for light-dependent enzyme modulation involves membrane-bound cyst(e)ine-containing proteins, designated 'light effect mediators' or 'LEMs'-components proposed to occur in the oxidized (disulfide) state in the dark and in the reduced (sulfhydryl) state in the light [2,4]. It is visualized that chloroplasts contain two LEMs (both on the acceptor side of photosystem I) that, following reduction by non-cyclic electron transport, modulate enzymes of the stroma. One of the proposed LEM components can be solubilized from peas by extracting chloroplast membranes with a Zwittergent detergent [5,6]. In the presence of an artificial electron donor, ascorbate/ 2,6-dichlorophenolindophenol (DCPIP), the Zwittergent-treated chloroplast membranes promoted the photoregulation of NADP-malate dehydrogenase of the stroma. Photoregulation in this system was dependent on the solubilized protein fraction that, based on SDS gel electrophoresis, contained several protein components. In experiments designed to determine the effect of Zwittergent extraction on enzyme photoregulation by systems under investigation in our laboratory (i.e., the ferredoxin/thioredoxin and ferralterin systems

Purothionin: a seed protein with thioredoxin activity

Purothionins are basic proteins of -SOOOM, [l-3] that have 8 half-cystine residues bonded to form disulfide bridges [4-71. Purothionins occur in the seed endosperm of cereals such as wheat, barley and rye [8,9], and show the curious property of being toxic to animals, when injected intraperitoneally or intravenously [lo], and to certain yeasts [ 1 l] and cultured mammalian cells [ 121 when present in their growth media. T’he physiological function of purothionins has not been established. Purothionins show a chemical resemblance to thioredoxins a group of widely distributed multifunctional proteins oflowM,that undergo oxidation/reduction through the interconconversion of S-S/SH groups. Thioredoxins have been shown to function as regulatory proteins that alter enzyme activity through thiol redox changes [ 131. Thioredoxins appear to play a particularly important regulatory role in photosynthesis through their ability to link light to the activity of several key chloroplast enzymes [ 141. Because of the chemical similarity to thioredoxins, we considered it worthwhile to examine purothionin for thioredoxin activity. We now report that purothionin obtained from wheat endosperm (flour) can substitute for a specific thioredoxin from spinach chloroplasts in the activation of a photosynthetic enzyme. These findings provide a new in vitro assay for conveniently measuring purothionin activity and, in addition, constitute evidence that purothionins inay function as regulatory proteins.

Carbon Dioxide and the Regulation of Photosynthesis: Activities of Photosynthetic Enzymes and Carbonate Dehydratase (Carbonic Anhydrase) in Chlorella after Growth or Adaption in Different Carbon Dioxide Concentrations

The unicellular green alga Chlorella pyrenoidosa, after growth in air or 5 % (v/v) CO*2, has markedly differing rates of photosynthesis in the presence of very low concentrations of CO*2. It was proposed that the differences could be accounted for by differences in the activities of ribulosebisphosphate carboxylase or other enzymes of the reductive pentose phosphate pathway. This hypothesis was tested and it was shown that between the two types of cells there were no significant differences in the activities of ribulosebisphosphate carboxylase (EC 4.1.1.39), phosphoenolpyruvate carboxylase (EC 4.1.1.31), phosphoenolpyruvate carboxykinase (ATP) (EC 4.1.1.49), glyceraldehyde-phosphate dehydrogenase (NADP) (EC 1.2.1.9), hexosebisphosphatase (EC 3.1.3.11), fructose-bisphosphate aldolase (EC 4.1.2.13), ribosephosphate isomerase (EC 5.3.1.6) and phosphoribulokinase (EC 2.7.1.19). There was also no difference between air-grown and 5% CO*2-grown cells in the content of fraction I protein isolated by disc gel electrophoresis and measured by a colorimetric procedure. A fivefold or sixfold increase in rate of photosynthesis occurs during about 90 min when 5% CO*2-grown Chlorella is illuminated in the presence of a very low CO*2 concentration (approximately 1 �M free CO*2, which is about one-tenth the concentration of CO*2 in distilled water in equilibrium with air). During this increase, the only photosynthetic enzyme to change in activity was carbonate dehydratase (carbonic anhydrase, EC 4.2.1.1). This enzyme was absent from cells grown with 5% CO*2 but was present in air-grown cells. The enzyme appears to be induced by low CO*2 concentrations and repressed by high concentrations. It was concluded that carbonate dehydratase plays a major regulatory role in photosynthesis in Chlorella at low CO*2 concentrations.

Wavelength dependence of electron flow and oxygen evolution in isolated chloroplasts: A possible role for carotenoids

A previously unreported stimulation of Hill activity in isolated spinach chloroplasts by long wave (> 570 nm) light and an inhibition by short wave (> 360 < 550 nm) light has been demonstrated.The effect is particularly pronounced in the presence of the uncoupling agents, methylamine, NH 4Cl and qiuinacrine. Both electron transfer, and oxygen liberation, respond similarly to wavelength. It is suggested that both the stimulatory and inhibitory effects can be explained by the relative state of photoxidation of the blue-absorbing component, possibly a carotenoid. A potential regulatory role in photosynthesis is postulated for this unidentified constituent of chloroplast membranes.