psbA Gene Research Articles

Molecular signatures of environmental adaptation mechanisms of Rhizocarpon geographicum in Horseshoe Island (west of the Antarctic Peninsula) and Türkiye

The adaptation of lichen species to different habitats and extreme conditions is due to rapid changes in expressions of the genes in their genetic backgrounds. In this study, lichen samples were collected from two different regions: from Horseshoe Island, located to the west of the Antarctic Peninsula and from the west coast of Türkiye. The nrITS gene regions of the samples were studied and the phylogenetic positions of the samples were confirmed as Rhizocarpon geographicum (L.) DC. After DNA barcoding of R. geographicum, expression differences of three below-specified stress genes were revealed. Comparative determinations of the changes in the expressions of the multiprotein binding factor-1 (MBF-1), polyketide synthase (PKS), and photosystem II D1 protein (psbA) genes due to temperature or other environmental stress change stress were performed by a real-time PCR. Specifically, under cold stress conditions such as those found on Horseshoe Island, the MBF-1 gene was highly expressed, while PKS and psbA gene expression levels were lower compared to the west coast of Türkiye. The results of this study, which is the first in its field, highlight the adaptation of Rhizocarpon geographicum specimens to those habitats and regional climate. Specimen collected from different geographical regions exhibited gene expression differences.

Herbicide-resistant plants produced by precision adenine base editing in plastid DNA.

CRISPR-free, protein-only cytosine base editors (CBEs) or adenine base editors, composed of DNA-binding proteins such as zinc finger proteins or transcription activator-like effectors (TALEs) and nucleobase cytosine or adenine deaminases, respectively, enable organellar DNA editing in cultured cells, animals and plants1-4. TALE-linked double-stranded DNA deaminase toxin A (DddAtox)-derived CBEs (DdCBEs) and TALE-linked adenine deaminases (TALEDs) install C-to-T and A-to-G single-nucleotide conversions, respectively, in mitochondria and chloroplasts5-9. Interestingly, whereas TALEDs exclusively induce A-to-G conversions without C-to-T conversions in mammalian mitochondrial DNA10, they often install unwanted C-to-T edits in addition to intended A-to-G edits in plastid DNA7,9,11,12. Here we show that uracil DNA glycosylase (UDG)-fused TALEDs (UDG-TALEDs) minimize C-to-T conversions without reducing the A-to-G editing efficiency and install a mutation in the chloroplast psbA gene that encodes a single-amino-acid substitution (S264G), which confers herbicide resistance in the resulting plants.

A novel AP2/ERF transcription factor, NtERF10, positively regulates plant height in tobacco

Ethylene response factors have been shown to be involved in the effects of plant developmental processes and to regulate stress tolerance. The aim of this study was to recognize the regulatory mechanisms of ethylene response factors on tobacco plant height. In this study, a gene-edited mutant (ERF10-KO) and wild type (WT) were utilized as experimental materials. Transcriptome and metabolome analyses were used to investigate the regulatory mechanism of NtERF10 gene editing on plant height in tobacco. Here, through the analysis of differentially expressed genes (DEGs), 2051 genes were upregulated and 1965 genes were downregulated. We characterized the different ERF10-KO and WT plant heights and identified key genes for photosynthesis, the plant hormone signal transduction pathway and the terpene biosynthesis pathway. NtERF10 was found to affect the growth and development of tobacco by regulating the expression levels of the PSAA, PSBA, GLY17 and GGP3 genes. Amino acid metabolism was analyzed by combining analyses of differentially expressed genes (DEGs) and differentially accumulated metabolites (DAMs). In addition, we found that members of the bHLH, NAC, MYB, and WRKY transcription factor families have vital roles in regulating plant height. This study not only provides important insights into the positive regulation of the ethylene response factor NtERF10 on plant height during plant growth and development but also provides new research ideas for tobacco molecular breeding.

The local phytoplankton community in Shizugawa Bay, Japan, from 2021 to 2022: analysis by DNA metabarcoding

ABSTRACT This study was conducted in Shizugawa Bay, located on the north-eastern coast of Japan, to determine phytoplankton assemblages. Metabarcoding with the PsbA gene and environmental surveys were conducted from May 2021 to January 2022. PCA results showed that phytoplankton assemblages changed with the environmental parameters, such as water temperature and salinity, indicating a clear seasonal pattern. The relative abundance was dominated by Chlorophyta (annual mean 34.9%) > Bacillariophyta (29.1%) > Haptophyta (17.8%) > Dinophyceae (11.7%). It is suggested that many species of Chlorophyta remain without being filtered by shellfish because the dominant representatives were pico-prasinophytes, which are of small size and are difficult for shellfish to capture. Bacillariophytes are thought to have been consumed preferentially since they are known to be a good food source for adult shellfish. Among Dinophyceae, Dinophysis spp. (causing diarrheal poisoning) were dominant throughout the period, while Alexandrium spp. (causing paralytic poisoning) showed relatively low abundance. Phaeocystis spp. (including some toxic species) were the dominant haptophytes. Cyanobacteria tended to appear particularly in summer although their mean relative abundance was less than 3%. Although the data are limited, they provide a useful snapshot of phytoplankton assemblages in Shizugawa Bay and the environmental factors that affect them.

Diversity and Abundance of Non-Geniculate Coralline Algae (NGCA) in Different Reef Conditions and Depth Zones

Non-g eniculate coralline red algae (NGCA) provide habitats for many epiphytic fauna and flora, and are considered reef engineers. The identification of NGCA is challenging due to cryptic speciation and their phenotypic plasticity that can be mediated by environmental conditions. Using DNA sequence data (psbA gene), a systematic examination was undertaken of the diversity and abundance of NGCA from two different reef conditions (fair and poor reef) and depth zones (shallow and deep zone) of a subtidal reef in the Gulf of Thailand at Koh Taen, Surat Thani Province, Thailand. Phylogentic analysis revealed 11 putative species: Chamberlainium sp., Dawsoniolithon sp., Hydrolithon boergesenii, Lithophyllum sp.1, Lithophyllum sp.2, Neogoniolithon sp.1, Neogoniolithon sp.2, Parvicellularium sp., Sporolithon ptychoides, Sporolithon sp.1 and Sporolithon sp.2. Specimens attributed to a newly recorded genus Parvicellularium, showed its highest abundance in the deep zone, while specimens attributed to Lithophyllum and Sporolithon were dominant in the shallow zone. The abundance of all NGCA genera showed no significant differences among reef conditions. Here, we present an updated overview of the diversity and abundance of NGCA in Thai waters.

Cloning and functional characterization of the peptide deformylase encoding gene EuPDF1B from Eucommia ulmoides Oliv

Peptide deformylase can catalyse the removal of formyl groups from the N-terminal formyl methionine of the primary polypeptide chain. The peptide deformylase genes of a few herbaceous plants have been studied to some extent, but the peptide deformylase genes of woody plants have not been studied. In this study, we isolated EuPDF1B from Eucommia ulmoides Oliv. The full-length sequence of EuPDF1B is 1176 bp long with a poly-A tail and contains an open reading frame of 831 bp that encodes a protein of 276 amino acids. EuPDF1B was localized to the chloroplast. qRT‒PCR analysis revealed that this gene was expressed in almost all tissues tested but mainly in mature leaves. Moreover, the expression of EuPDF1B was enhanced by ABA, MeJA and GA and inhibited by shading treatment. The expression pattern of EuPDF1B was further confirmed in EuPDF1Bp: GUS transgenic tobacco plants. Among all the transgenic tobacco plants, EuPDF1Bp-3 showed the highest GUS histochemical staining and activity in different tissues. This difference may be related to the presence of enhancer elements in the region from − 891 bp to − 236 bp of the EuPDF1B promoter. In addition, the expression of the chloroplast gene psbA and the net photosynthetic rate, fresh weight and height of tobacco plants overexpressing EuPDF1B were greater than those of the wild-type tobacco plants, suggesting that EuPDF1B may promote the growth of transgenic tobacco plants. This is the first time that PDF and its promoter have been cloned from woody plants, laying a foundation for further analysis of the function of PDF and the regulation of its expression.

Two new species of Dictyota (Dictyotales, Phaeophyceae), D. dimorphosa sp. nov. and D. recumbens sp. nov., based on morphological and molecular investigations

ABSTRACT The brown algal genus Dictyota (Dictyotales, Phaeophyceae) is widespread, particularly in warm temperate and tropical waters, and plays a vital role in coastal ecosystems. This study reassessed the taxonomy of Dictyota, focusing on specimens from Myanmar and Japan, using a combination of morphological and molecular analyses. Molecular phylogenetic analyses using concatenated DNA sequences of rbcL, psaA, psbA, cox1 and cox3 genes revealed that Dictyota specimens from Myanmar, Japan, and other regions, belong to nine different clades, each representing a different species. Based on morphological and molecular data, seven out of these nine clades are identified as known species, while the remaining two clades are described as new species D. recumbens sp. nov. (=D. sp. A) and D. dimorphosa sp. nov. (=D. sp. B). Dictyota recumbens is characterized by the recumbent thallus, with transverse yellowish-green iridescent lines, and the formation of solitary spores irregularly distributed over the thallus. Dictyota dimorphosa is characterized by two morphological forms: decumbent and erect thalli, with bluish iridescence mainly in the decumbent thallus, and the formation of spores in oval ring shapes distributed over both thallus surfaces. Dictyota recumbens was typically found in tropical regions, while D. dimorphosa appears to be a cool-warm temperate species, distributed from northeastern Hokkaido to southern Kyushu with an extension along South Korea. Our molecular phylogenetic analyses have revealed the existence of several species whose names appeared in multiple clades, suggesting the potential for future increases in species diversity and the presence of cryptic species within certain groups.

Phymatolithopsis acervata comb. nov., and P. roseola sp. nov. (Hapalidiales, Rhodophyta) from South Africa with a comment on infraordinal classification

Abstract Phymatolithon acervatum is an encrusting, non-geniculate coralline alga from South Africa. While morpho-anatomical details of the species are well documented, no genetic analyses have been performed on P. acervatum. Here, we analyzed rbcL and psbA gene sequences, and they showed that two species were passing under the name Phymatolithon acervatum in South Africa. A partial rbcL sequence from the lectotype of Lithothamnion acervatum, basionym of P. acervatum, showed to which species the specific epithet applies, and furthermore that both species belong in Phymatolithopsis. We transfer Phymatolithon acervatum to Phymatolithopsis, as Phymatolithopsis acervata comb. nov., and propose Phymatolithopsis roseola sp. nov. These species overlap in morpho-anatomy, habitat and distribution and can only be distinguished based on DNA sequences. Previous misinterpretations of conceptacle development are corrected for species of Phymatolithopsis. The main character used to define the family Mesophyllumaceae is shown to have arisen several times in independent lineages in the order Hapalidiales. At present, only one family, Hapalidiaceae, thus merits recognition in the Hapalidiales.

From cyanobacteria and cyanophages to chloroplasts: the fate of the genomes of oxyphototrophs and the genes encoding photosystem II proteins.

Chloroplasts are the result of endosymbiosis of cyanobacterial organisms with proto-eukaryotes. The psbA, psbD and psbO genes are present in all oxyphototrophs and encode the D1/D2 proteins of photosystem II (PSII) and PsbO, respectively. PsbO is a peripheral protein that stabilizes the O2-evolving complex in PSII. Of these genes, psbA and psbD remained in the chloroplastic genome, while psbO was transferred to the nucleus. The genomes of selected cyanobacteria, chloroplasts and cyanophages carrying psbA and psbD, respectively, were analysed. The highest density of genes and coding sequences (CDSs) was estimated for the genomes of cyanophages, cyanobacteria and chloroplasts. The synonymous mutation rate (rS) of psbA and psbD in chloroplasts remained almost unchanged and is lower than that of psbO. The results indicate that the decreasing genome size in chloroplasts is more similar to the genome reduction observed in contemporary endosymbiotic organisms than in streamlined genomes of free-living cyanobacteria. The rS of atpA, which encodes the α-subunit of ATP synthase in chloroplasts, suggests that psbA and psbD, and to a lesser extent psbO, are ancient and conservative and arose early in the evolution of oxygenic photosynthesis. The role of cyanophages in the evolution of oxyphototrophs and chloroplastic genomes is discussed.

Effect of Metal Nanoparticles on Photosynthetic and Antioxidant Enzyme Activities of Soybean

This study presents the effects of nanoscale zerovalent cobalt (NZVC) on the photosynthetic activity and expression of genes related to the photosynthetic apparatus as well as the activity of antioxidant enzymes in soybean (Glycine max L. Merr). Treatment of soybean seeds with NZVC solution (at concentrations of 0.17; 0.33 and 100 mg/kg seed) has increased the efficiency of light energy absorbed by photosystem II, improved photosynthetic efficiency, and maintained the function of photosynthetic apparatus when plant growth is reduced by enhancing the value of photosynthetic parameters (Fo, Fm, Fv/Fm, ETR, FPSII) compared with the control. The expression of genes involved in photosynthesis in soybean leaves was changed by growth time and NZVC treatment concentration. The psaA, Lhca, psbA, and psbB genes had increased expression levels at 17 and 32 days after sowing, then decreased at 70 days after sowing. The expression of the psbE, and Cyt b6f genes was greater than the control during the growth period. Treatment of soybean seeds with high concentrations of NZVC (0.33 and 100 mg/kg seed) did not negatively affect the photosynthetic function of soybean plants. The activity of nitrate and nitrite reductases and antioxidant enzymes including superoxide dismutase, catalase, peroxidase, and ascorbate peroxidase of cobalt-treated plants were better than those of the control. This is a defense mechanism of plants to minimize the harmful effects of these stresses. This result has elucidated the mechanism of increasing the yield of soybean when its seeds were treated with NZVC.

Effect of Acclimation to High Temperatures on the Mechanisms of Drought Tolerance in Species with Different Types of Photosynthesis: Sedobassia sedoides (C3–C4) and Bassia prostrata (C4-NADP)

The effect of drought on the morphophysiological, biochemical, and molecular genetic parameters of plants Sedobassia sedoides (Pall.) Freitag G. Kadereit with an intermediate C3–C4-type of photosynthesis and Bassia prostrata (L.) A.J. Scott with a C4-NADP type of photosynthesis grown at different temperatures (25 and 30°C) was studied. A decrease in the biomass, water content, and effective quantum yield (ΦPSII) of PSII, as well as an increase in the expression of the psbA gene encoding the PSII D1 protein under the action of drought, was observed in both species regardless of the growing temperature. Both species showed a decrease in the content of photosynthetic enzymes ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and phosphoenolpyruvate carboxylase (PEPC) under drought conditions at 25°С, which was accompanied by a significant increase in the expression of the rbcL and PPDK genes in S. sedoides. Acclimation of S. sedoides plants to elevated temperatures led to an increase in the activity of cyclic electron transport around PSI, to mitigation of the negative effect of drought on the light reactions of photosynthesis (reduction in NPQ) and the content of the PEPC enzyme, as well as to a shift in the ionic balance caused by a decrease in the potassium content. B. prostrata showed greater drought resistance and was characterized by greater thermolability of photosynthetic enzymes, changes in the content and ratio of which allowed this species to maintain growth in drought conditions at different temperatures.

Ethylene and spermine attenuate chromium-inhibited photosynthetic functions by improving nitrogen and sulfur assimilation and antioxidant system in mustard

Phytohormones signaling is known for the regulation of metabolites synthesis, photosynthetic performance and abiotic stress acclimation in plants. We investigated the influence of ethylene (sourced as ethephon; 2-chloroethyl phosohonic acid, ETH) and spermine (Spm; polyamine) in alleviating the chromium (Cr)-triggered oxidative stress in the mustard (Brassica juncea cv. Varuna). The individual additions of 200 µL L−1 ETH and 1 mM Spm improved photosynthetic and growth parameters in the absence of Cr, but the Cr presence increased oxidative stress and the formation of stress (excess) ethylene, inhibiting photosynthesis, and growth. The application of ETH and Spm together in the absence of Cr, improved photosynthesis conspicuously. In the presence of Cr, ETH and Spm application improved photosynthesis by upregulation of psbA and psbB genes expression, and reducing oxidative stress, stress ethylene formation, and increase in activity of antioxidant enzymes, upregulation of ascorbate peroxidase (APX) and glutathione reductase (GR) genes, and nitrogen (N) and sulfur (S) assimilation. The possible ways in which ethylene and Spm interact in the mitigation of Cr-triggered oxidative damage are discussed. The study will provide insight into the mechanisms of N and S assimilation, antioxidant system, and regulation of ethylene production under the influence of ETH and Spm, and the strategy may be adopted for the sustainability of mustard plants under Cr stress.

Expression of the far-red D1 protein or introduction of conserved far-red D1 residues into Synechocystis sp. PCC 6803 impairs Photosystem II.

The wavelengths of light harvested in oxygenic photosynthesis are ~400-700 nm. Some cyanobacteria respond to far-red light exposure via a process called far-red light photoacclimation which enables absorption of light at wavelengths >700 nm and its use to support photosynthesis. Far-red-light-induced changes include up-regulation of alternative copies of multiple proteins of Photosystem II (PS II). This includes an alternative copy of the D1 protein, D1FR . Here, we show that D1FR introduced into Synechocystis sp. PCC 6803 (hereafter Synechocystis 6803) can be incorporated into PS II centres that evolve oxygen at low rates but cannot support photoautotrophic growth. Using mutagenesis to modify the psbA2 gene of Synechocystis 6803, we modified residues in helices A, B, and C to be characteristic of D1FR residues. Modification of the Synechocystis 6803 helix A to resemble the D1FR helix A, with modifications in the region of the bound ß-carotene (CarD1 ) and the accessory chlorophyll, ChlZD1 , produced a strain with a similar phenotype to the D1FR strain. In contrast, the D1FR changes in helices B and C had minor impacts on photoautotrophy but impacted the function of PS II, possibly through a change in the equilibrium for electron sharing between the primary and secondary plastoquinone electron acceptors QA and QB in favour of QA - . The addition of combinations of residue changes in helix C indicates compensating effects may occur and highlight the need to experimentally determine the impact of multiple residue changes.

Confirmation of a five‐way herbicide‐resistant Amaranthus tuberculatus population in North Carolina

AbstractAmaranthus tuberculatus (waterhemp) is a pervasive weed of the Mid‐west and ‐south United States and is not native to North Carolina but infestations in crop fields have been reported recently. Amaranthus tuberculatus has evolved resistance to seven herbicide groups and multiple herbicide‐resistant populations are common where the species is native. The reported A. tuberculatus infestations in North Carolina have not been controlled with herbicides but no formal herbicide resistance characterisation has been conducted to date. Glasshouse dose–response experiments were conducted to determine the susceptibility of a population collected from Surry County, North Carolina to commonly applied postemergence herbicides compared to a herbicide‐susceptible population collected from Story County, Iowa. The Surry County population survived labelled rates of imazethapyr, atrazine, glyphosate, fomesafen, and mesotrione; the Story County population was controlled with these herbicides. Further, 2,4‐D, dicamba, and glufosinate effectively controlled the Surry and Story County populations. Molecular sequencing assays were subsequently conducted to determine if altered target sites facilitated resistance in the acetolactate synthase (ALS), 5‐enolpyruvylshikimate‐3‐phosphate synthase (EPSPS), photosystem II (psbA), and protoporphyrinogen oxidase (PPX2) genes. The Surry County population carried a Trp574Leu and ∆Gly210 mutations in the ALS and PPX2 gene, respectively. No mutations that would confer resistance were found in the EPSPS or psbA gene for either population. The results of both experiments provide evidence that a five‐way herbicide‐resistant A. tuberculatus population has encroached North Carolina. More research is needed to determine the mechanisms of resistance to atrazine, glyphosate, and mesotrione.

Asia Pacific Sporolithon (Corallinophycidae, Rhodophyta) species revised based on DNA sequencing of type specimens and including S. crypticum sp. nov., S. immotum sp. nov. and S. nodosum sp. nov.

ABSTRACTTo address the taxonomic uncertainty of Sporolithon species named in the early to mid-20th century, targeted PCR sequencing was performed on eight historical type specimens and on recently collected specimens. Six type specimens amplified for the rbcL gene and were Sanger sequenced yielding sequences ranging in length from 118 to 280 base pairs (bp). One, S. australasicum, failed to amplify and another, S. howei, was amplified for the psbA gene yielding a sequence 544 bp in length. The 118 bp long rbcL sequence of the lectotype of S. crassiramosum showed that it is a later, heterotypic synonym of S. molle. The rbcL sequences of type specimens of S. episoredion, S. schmidtii, S. sibogae and S. timorense ranged from 118 to 228 bp, and each is a distinct species. The 544 bp long psbA sequence of S. howei is also unique. The 280 bp long rbcL sequence of the lectotype of S. durum did not match any sequence with that name in any public repository, including the previously published complete plastome and mitogenome sequences. However, it was identical in sequence to a specimen in GenBank from the southern coast of Western Australia as well as several other sequences generated from field-collected specimens from the states of South Australia and Western Australia. The rhodolith specimens from New Zealand previously called S. durum are S. nodosum sp. nov. The species is endemic to New Zealand. The epilithic specimens from New Zealand previously called S. durum are S. immotum sp. nov., which is also found along the southeastern coast of Australia. Sporolithon crypticum sp. nov. is described from the southern coast of Western Australia. RAxML and Bayesian phylogenetic analyses of Sporolithon psbA and rbcL sequences are congruent between the two plastid encoded genes. DNA sequencing of type specimens of species of corallines is demonstrated to be the only reliable method to correctly apply names.

Taxonomic contributions to Hapalidiales (Corallinophycidae, Rhodophyta): Boreolithothamnion gen. nov., Lithothamnion redefined and with three new species and Roseolithon with new combinations.

Phylogenetic analyses of rbcL gene sequences and of concatenated rbcL, psbA, and nuclear SSU rRNA gene sequences resolved the generitype of Lithothamnion, L. muelleri, in a clade with three other southern Australian species, L. kraftii sp. nov., L. saundersii sp. nov., and L. woelkerlingii sp. nov. Cold water boreal species currently classified in Lithothamnion and whose type specimens have been sequenced are transferred to Boreolithothamnion gen. nov., with B. glaciale comb. nov. as the generitype. The other species are B. giganteum comb. nov., B. phymatodeum comb. nov., and B. sonderi comb. nov., whose type specimens are newly sequenced, and B. lemoineae comb. nov., B. soriferum comb. nov., and B. tophiforme comb. nov., whose type specimens were already sequenced. Based on rbcL sequences from the type specimens of Lithothamnion crispatum, L. indicum, and L. superpositum, each is recognized as a distinct species and transferred to the recently described Roseolithon as R. crispatum comb. nov., R. indicum comb. nov., and R. superpositum com. nov., respectively. To correctly assign species to these three genera based only on morpho-anatomy, specimens must have multiporate conceptacles and some epithallial cells with flared walls. The discussion provides examples demonstrating that only with phylogenetic analyses of DNA sequences can the evolution of morpho-anatomical characters of non-geniculate corallines be understood and applied at the correct taxonomic rank. Finally, phylogenetic analyses of DNA sequences support recognition of the Hapalidiales as a distinct order characterized by having multiporate tetra/bisporangial conceptacles, and not as a suborder of Corallinales whose tetra/bisporangial conceptacles are uniporate.

Impact of Salinity, Elevated Temperature, and Their Interaction with the Photosynthetic Efficiency of Halophyte Crop Chenopodium quinoa Willd

Chenopodium quinoa is a genetically diverse crop that can adapt to a wide range of environments, including temperatures and salinities. However, only a few studies have assessed the combined effects of two or more environmental factors on C. quinoa. Here, we investigated the effects of salinity (300 mM NaCl), elevated temperature (35 °C), and their interaction with growth, water–salt balance, the efficiency of photosystem II (PSII), the activity of cyclic electron transport (CET) around photosystem I (PSI), Rubisco and PEPC enzyme content, and the expression of photosynthetic genes. We found that elevated temperature did not decrease the biomass but caused a significant increase in the water and potassium content of C. quinoa leaves. The decrease in PSII efficiency under elevated temperature was accompanied by an increase in the expression of genes encoding the components of PSII (psbA) and linear electron transport (FDI), as well as the main photosynthetic protein Rubisco (rbcL). Moreover, the strongest effect was induced by the combined effect of elevated temperature and salinity, which induced high oxidative stress (a threefold increase in MDA), a threefold decrease in the biomass, a twofold decrease in PSII efficiency, and a two- to eightfold decrease in the expression of the photosynthetic genes psbA, FDI, and rbcL. PSI was more tolerant to all forms of stress; however, the combined effect of elevated temperature and salinity downregulated the expression of PGR5 and FNR1, which may diminish the role of PGR5/PGRL1-dependent CET in favor of the NDH-dependent CET of PSI. The obtained data on the functioning of photosystems and the expression of photosynthetic genes under combined stress (elevated temperature and salinity) can make a significant contribution to understanding the mechanisms of tolerance of C. quinoa to multiple stresses under climate change conditions.

Evaluation of the Effects of Different Phosphorus Sources on Microcystis aeruginosa Growth and Microcystin Production via Transcriptomic Surveys

Microcystis aeruginosa (M. aeruginosa) is a dominant species among frequent cyanobacterial blooms and is well known for its toxin-producing ability. Phosphorus (P) is a typical growth-limiting element for M. aeruginosa. Although alterations in physiological reactions have been documented in response to various P sources, the underlying molecular processes and transcriptional patterns remain poorly understood. This study evaluated the physiological and molecular responses of M. aeruginosa to different P sources. The growth of M. aeruginosa was promoted by both dissolved inorganic phosphorus (DIP) and dissolved organic phosphorus (DOP) at a concentration of 0.4 mg/L with an initial cell density of 1.50 (±0.05) × 106 cells/mL. The cell density reached 1.38 (±0.05) × 107 cells/mL in the DIP group on day 14, a value which was higher than that in the DOP group. Most photosynthesis genes had higher levels of upregulated expression in the DIP group. For instance, gene psbA was upregulated by 0.45 Log2Fold Change (Log2FC). In the DOP group, it is interesting that the Pi (PO4-P) concentration increased to 0.09 mg/L on day 14. Meanwhile, the expression of the gene encoding alkaline phosphatase-like protein was significantly upregulated, with a value of 1.56 Log2FC, and the alkaline phosphatase concentration increased in the DOP group. The intracellular microcystin (IMC) concentration decreased with time in both groups. However, the concentration of extracellular microcystins (EMCs) increased with incubation time in both groups. Phosphorus participates in the regulation of microcystin synthesis, mainly by regulating ATP synthesis. Based on the physiological and molecular investigations in this study, the results provide crucial insights into the physiological adaptations and the role of P in modulating harmful algal bloom formation, microcystin synthesis, and potential molecular responses of M. aeruginosa.

Effect of nano-calcium carbonate on morphology, antioxidant enzyme activity and photosynthetic parameters of wheat (Triticum aestivum L.) seedlings

To meet the human demand for crop productivity, there are several challenges that researchers are involved in the photosynthetic efficiency of plants may be one of them. Nanotechnology can improve agricultural productivity by affecting the photosynthetic activity of plants. However, no studies have yet shown that nano-calcium carbonate (NCC) can play a role in improving photosynthetic performance of plants. In order to explore the effects of NCC on wheat seedling morphology, antioxidant enzyme activities and photosynthetic parameters, wheat roots were exposed to different concentrations of NCC (0, 25, 50, 100, 200, 400 mg L−1) through hydroponic experiments. Different concentrations affected root length, root surface area, root diameter, root volume and plant dry biomass. Compared to the control (0 mg L−1 of NCC) application (CK), wheat with 200 mg L−1 of NCC application showed 54% and 58% increase in superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities, respectively. As for photosynthesis-related physiological indicators, compared with CK, 200 mg L−1 of NCC significantly enhanced chlorophyll a (38%), chlorophyll b (20%), carotenoid content (19%), Rubisco activity (3.02-fold), net photosynthetic rate (Pn, 56%), transpiration rate (Tr, 40%), and stomatal conductance (Gs, 71%). The PCR results showed that compared with CK, the psbA gene encoding the photosystem PSII reaction center D1 protein and the rbcL gene encoding the large subunit of Rubisco were up-regulated by 2.56- and 2.58-fold at 200 mg L−1 NCC treatment, and by 3.22- and 3.57-fold at 400 mg L−1 NCC treatment, respectively. Specifically, NCC has significant benefits on wheat seedling growth, and 200 mg L−1 is the optimal concentration. NCC enhanced photosynthetic performance of wheat by increasing antioxidant enzyme activity, photosynthetic pigment content, Rubisco activity, stomatal conductance and PSII reaction center activity.Graphical

Viruses of sulfur oxidizing phototrophs encode genes for pigment, carbon, and sulfur metabolisms

Viral infections modulate bacterial metabolism and ecology. Here, we investigated the hypothesis that viruses influence the ecology of purple and green sulfur bacteria in anoxic and sulfidic lakes, analogs of euxinic oceans in the geologic past. By screening metagenomes from lake sediments and water column, in addition to publicly-available genomes of cultured purple and green sulfur bacteria, we identified almost 300 high and medium-quality viral genomes. Viruses carrying the gene psbA, encoding the small subunit of photosystem II protein D1, were ubiquitous, suggesting viral interference with the light reactions of sulfur oxidizing autotrophs. Viruses predicted to infect these autotrophs also encoded auxiliary metabolic genes for reductive sulfur assimilation as cysteine, pigment production, and carbon fixation. These observations show that viruses have the genomic potential to modulate the production of metabolic markers of phototrophic sulfur bacteria that are used to identify photic zone euxinia in the geologic past.