Photodynamically Tumor Vessel Destruction Amplified Tumor Targeting of Nanoparticles for Efficient Chemotherapy

Efficient tumor-targeted drug delivery is still a challenging and currently unbreakable bottleneck in chemotherapy for tumors. Nanomedicines based on passive or active targeting strategy have not yet achieved convincing chemotherapeutic benefits in the clinic due to the tumor heterogeneity. Inspired by the efficient inflammatory-cell recruitment to acute clots, we constructed a two-component nanosystem, which is composed of an RGD-modified pyropheophorbide-a (Ppa) micelle (PPRM) that mediates the tumor vascular-targeted photodynamic reaction to activate local coagulation and subsequently transmits the coagulation signals to the circulating clot-targeted CREKA peptide-modified camptothecin (CPT)-loaded nanodiscs (CCNDs) for amplifying tumor targeting. PPRM could effectively bind with the tumor vasculature and induce sufficient local thrombus by a photodynamic reaction. Local photodynamic reaction-induced tumor target amplification greatly increased the tumor accumulation of CCND by 4.2 times, thus significantly enhancing the chemotherapeutic efficacy in the 4T1 breast tumor model. In other words, this study provides a powerful platform to amplify tumor-specific drug delivery by taking advantage of the efficient crosstalk between the PPRM-activated coagulation cascade and clot-targeted CCND.

Photosensitizer-thioglycosides enhance photodynamic therapy by augmenting cellular uptake

Photodynamic therapy (PDT) uses photosensitizing agents along with light to ablate tissue, including cancers. Such light-driven localized delivery of free-radical oxygen to kill target tissue depends on photosensitizer cell penetration efficacy. While the attachment of monosaccharides and disaccharides to photosensitizers has been shown to potentially provide improved photosensitizer delivery, the range of glycan entities tested thus far is limited. We sought to expand such knowledge by coupling N-acetylglucosamine (GlcNAc) to pyropheophorbides as thioglycosides, and then testing photosensitizer efficacy. To this end, GlcNAc was conjugated to both pyropheophorbide-a and methyl pyropheophorbide-a. Among the entities tested, the conjugation of N-acetylglucosamine to methyl pyropheophorbide-a ('PSe') as thioglycoside enhanced cell uptake both in the presence and absence of human serum proteins, relative to other compounds tested. The enhanced PSe penetrance into cells resulted in higher cell death upon illumination with 665 nm light. While acting as a potent photosensitizer, PSe did not affect cellular carbohydrate profiles. Overall, the study presents a new pyropheophorbide glycoconjugate with strong in vitro PDT efficacy.

Exploring the potential of pheophorbide A, a chlorophyll-derived compound in modulating GLUT for maintaining glucose homeostasis

Introduction

Pheophorbide A, a chlorophyll-breakdown product, is primarily investigated for its anti-oxidant and anti-inflammatory activity. Recent reports on pheophorbide A have shown its potential in lowering blood glucose levels, thus leading to the exploration of its use in diabetes management. Literature has also shown its effect on enhanced insulin secretion, whereas its mechanism on glucose stimulated insulin secretion (GSIS) in pancreatic β cells remains unexplored.

Methods

In-silico and in-vitro investigations were used to explore the effect of pheophorbide A on class I glucose transporters (GLUTs). In-silico studies include - Molecular docking studies and stability assessment using GROMACS. In-vitro studies include - MTT assay, Glucose uptake assay, Live-cell imaging and tracking of GLUTs in presence of Pheophorbide A compared to control.

Results

Molecular docking studies revealed better binding affinity of pheophorbide A with GLUT4 (-11.2 Kcal/mol) and GLUT1 (-10.7 Kcal/mol) when compared with metformin (-5.0 Kcal/mol and -4.9 Kcal/mol, respectively). Glucose levels are largely regulated by GLUTs where GLUT1 is one of the transporters that is ubiquitously present in human β cells. Thus, we confirmed the stability of the complex, that is, pheophorbide A-GLUT1 using GROMACS for 100 ns. We further assessed its effect on a pancreatic β cell line (INS-1) for its viability using an MTT assay. Pheophorbide A (0.1-1 µM) showed a dose-dependent response on cell viability and was comparable to standard metformin. To assess how pheophorbide A mechanistically acts on GLUT1 in pancreatic β cell, we transfected INS-1 cells with GLUT1-enhanced green fluorescent protein and checked how the treatment of pheophorbide A (0.50 µM) modulates GLUT1 trafficking using live-cell imaging. We observed a significant increase in GLUT1 density when treated with pheophorbide A (0.442 ± 0.01 µm-2) at 20 mM glucose concentration when compared to GLUT1 control (0.234 ± 0.01 µm-2) and metformin (0.296 ± 0.02 µm-2). The average speed and distance travelled by GLUT1 puncta were observed to decrease when treated with pheophorbide A. The present study also demonstrated the potential of pheophorbide A to enhance glucose uptake in β cells.

Conclusion

The current study's findings were validated by in-silico and cellular analyses, suggesting that pheophorbide A may regulate GLUT1 and might be regarded as a potential lead for boosting the GSIS pathway, thus maintaining glucose homeostasis.

Anti-adipogenic activities of pheophorbide a and pyropheophorbide a isolated from wild bitter gourd (Momordica charantia L. var. abbreviata Seringe) in vitro

BACKGROUND

The wild bitter gourd (WBG) is a commonly consumed vegetable in Asia that has antioxidant and hypoglycemic properties. The present study aimed to investigate the anti-adipogenic activities of isolated compounds from WBG on 8-day differentiated cultures of 3 T3-L1 adipocytes that were then stained with Oil Red O (ORO) or diamidino-2-phenylindole (DAPI).

RESULTS

ORO stains of the methanol extracts of de-seeded HM86 cultivar of WBG (WBG-M) and the ethyl acetate fractions (WBG-M-EA) showed anti-adipogenic activities against differentiated adipocytes. Two chlorophyll-degraded compounds, pheophorbide a (1) and pyropheophorbide a (2), were isolated from WBG-M-EA. Treatments with 1 (5, 10, and 20 μmol L^-1 ) and 2 (2.5, 5, and 10 μmol L^-1 ) showed dose-dependent reductions in lipid accumulations and reduced nuclear DAPI stains in differentiated 3 T3-L1 adipocytes. The concentrations for 50% inhibition against lipid accumulations of 1 and 2, respectively, were 16.05 and 7.04 μmol L^-1 . Treatments with 1 and 2 showed enhanced lactate dehydrogenase release in the first 4-day cell mitotic clonal expansions during the differentiating cultural processes, although the effect was less on the non-differentiating cultural processes. Thus, 1 and 2 were more toxic to differentiating adipocytes than to non-differentiated pre-adipocytes, which partly resulted in anti-adipogenic activities with lowered lipid accumulations.

CONCLUSION

Both 1 and 2 showed anti-adipogenic activities in cell models. These chlorophyll-degraded compounds commonly exist in several vegetables during storage or edible seaweeds, which will provide resources for further investigations aiming to test anti-obesity in animal studies. © 2022 Society of Chemical Industry.

Kovacikia minuta sp. nov. (Leptolyngbyaceae, Cyanobacteria), a new freshwater chlorophyll f-producing cyanobacterium

A few groups of cyanobacteria have been characterized as having far-red light photoacclimation (FaRLiP) that results from chlorophyll f (Chl f) production. In this study, using a polyphasic approach, we taxonomically transferred the Cf. Leptolyngbya sp. CCNUW1 isolated from a shaded freshwater pond, which produces Chl f under far-red light, to the genus Kovacikia and named this taxon Kovacikia minuta sp. nov. This strain was morphologically similar to Leptolyngbya-like strains. The thin filaments were purplish-brown under white light but became grass green under far-red light. The 31-gene phylogeny grouped K. minuta CCNU0001 into order Synechococcales and family Leptolyngbyaceae. Phylogenetic analysis based on 16S rRNA gene sequences further showed that K. minuta CCNU0001 was clustered into Kovacikia with similarities of 97.2-97.4% to the recently reported type species of Kovacikia muscicola HA7619-LM3. Additionally, the internal transcribed spacer region between 16S-23S rRNA genes had a unique sequence and secondary structure compared with other Kovacikia strains and phylogenetically related taxa. Draft genome sequences of K. minuta CCNU0001 (8,564,336 bp) were assembled into one circular chromosome and two circular plasmids. A FaRLiP 20-gene cluster comprised two operons with the unique organization. In sum, K. minuta was established as a new species, and it is the first species reported to produce Chl f and for which a draft genome was produced in genus Kovacikia. This study expanded our knowledge regarding the diversity of Chl f-producing cyanobacteria in far-red light-enriched environments and provides important foundational information for future investigations of FaRLiP evolution in cyanobacteria.

Protochlorophylls in Cucurbitaceae - Distribution, biosynthesis and phylogeny

Using high-resolution chromatography we resolved monovinyl (MV)- and divinyl (DV)-protochlorophylls (Pchls) and detected all of their side-chain homologues in the inner seed coat of Cucurbita maxima, C. pepo and their varieties. Furthermore, we analyzed other less common representatives of the Cucurbitaceae family that were found to accumulate mostly MV-Pchls. All these species and varieties showed the characteristic composition of individual Pchls. Additionally, we also detected all of the corresponding protopheophytins, which accounted for between 1.1 and 35.5% of Pchls and are supposed to be degradation products of Pchls, formed during seed storage. A pigment composition analysis of C. maxima seedlings performed during deetiolation revealed that chlorophyll (Chl) a content increased gradually, while the levels of Pchl-GG and Chl-GG, a precursor of Chl a, were low and did not change significantly. However, when the seedlings were incubated with the precursor of tetrapyrrole biosynthesis (δ-aminolevulinic acid) before illumination, the Chl-GG content increased dramatically, while synthesis of Chl a was inhibited. These data indicate that in C. maxima seedlings, Chl a is not synthesized from geranylgeranyl-pyrophoshate via Chl-GG, but rather directly from phytyl-pyrophosphate. Phylogenetic analysis of Chl synthase genes revealed that many species, including those of the Cucurbitaceae family, have two or more Chl synthase genes. This suggests that these additional genes, at least in some species, might encode isoforms involved in Pchl synthesis.

Chlorophyll f can replace chlorophyll a in the soluble antenna of dinoflagellates

Chlorophyll f is a new type of chlorophyll isolated from cyanobacteria. The absorption and fluorescence characteristics of chlorophyll f permit these oxygenic-photosynthetic organisms to thrive in environments where white light is scarce but far-red light is abundant. To explore the ligand properties of chlorophyll f and its energy transfer profiles we established two different in vitro reconstitution systems. The reconstituted peridinin-chlorophyll f protein complex (chlorophyll f-PCP) showed a stoichiometry ratio of 4:1 between peridinin and chlorophyll f, consistent with the peridinin:chlorophyll a ratio from native PCP complexes. Using emission wavelength at 712 nm, the excitation fluorescence featured a broad peak at 453 nm and a shoulder at 511 nm confirming energy transfer from peridinin to chlorophyll f. In addition, by using a synthetic peptide mimicking the first transmembrane helix of light-harvesting chlorophyll proteins of plants, we report that chlorophyll f, similarly to chlorophyll b, did not interact with the peptide contrarily to chlorophyll a, confirming the accessory role of chlorophyll f in photosystems. The binding of chlorophyll f, even in the presence of chlorophylls a and b, by PCP complexes shows the flexibility of chlorophyll-protein complexes and provides an opportunity for the introduction of new chlorophyll species to extend the photosynthetic spectral range.

The specificity of the bilin lyase CpcS for chromophore attachment to allophycocyanin in the chlorophyll f-containing cyanobacterium Halomicronima hongdechloris

Phycobilisomes are light-harvesting antenna complexes of cyanobacteria and red algae that are comprised of chromoproteins called phycobiliproteins. PBS core structures are made up of allophycocyanin subunits. Halomicronema hongdechloris (H. hongdechloris) is one of the cyanobacteria that produce chlorophyll f (Chl f) under far-red light and is regulated by the Far-Red Light Photoacclimation gene cluster. There are five genes encoding APC in this specific gene cluster, and they are responsible for assembling the red-shifted PBS in H. hongdechloris grown under far-red light. In this study, the five apc genes located in the FaRLiP gene cluster were heterologously expressed in an Escherichia coli reconstitution system. The canonical APC-encoding genes were also constructed in the same system for comparison. Additionally, five annotated phycobiliprotein lyase-encoding genes (cpcS) from the H. hongdechloris genome were phylogenetically classified and experimentally tested for their catalytic properties including their contribution to the shifted absorption of PBS. Through analysis of recombinant proteins, we determined that the heterodimer of CpcS-I and CpcU are able to ligate a chromophore to the APC-α/APC-β subunits. We discuss some hypotheses towards understanding the roles of the specialised APC and contributions of PBP lyases.

Self-Stabilized Supramolecular Assemblies Constructed from PEGylated Dendritic Peptide Conjugate for Augmenting Tumor Retention and Therapy

Supramolecular self-assemblies of dendritic peptides with well-organized nanostructures have great potential as multifunctional biomaterials, yet the complex self-assembly mechanism hampers their wide exploration. Herein, a self-stabilized supramolecular assembly (SSA) constructed from a PEGylated dendritic peptide conjugate (PEG-dendritic peptide-pyropheophorbide a, PDPP), for augmenting tumor retention and therapy, is reported. The supramolecular self-assembly process of PDPP is concentration-dependent with multiple morphologies. By tailoring the concentration of PDPP, the supramolecular self-assembly is driven by noncovalent interactions to form a variety of SSAs (unimolecular micelles, oligomeric aggregates, and multi-aggregates) with different sizes from nanometer to micrometer. SSAs at 100 nm with a spherical shape possess extremely high stability to prolong blood circulation about 4.8-fold higher than pyropheophorbide a (Ppa), and enhance tumor retention about eight-fold higher than Ppa on day 5 after injection, which leads to greatly boosting the in vivo photodynamic therapeutic efficiency. RNA-seq demonstrates that these effects of SSAs are related to the inhibition of MET-PI3K-Akt pathway. Overall, the supramolecular self-assembly mechanism for the synthetic PEGylated dendritic peptide conjugate sheds new light on the development of supramolecular assemblies for tumor therapy.

Journey of Poly(ethylene Glycol) in Living Cells

As the gold standard for stealth polymer materials, poly(ethylene glycol) (PEG) has been widely used in drug delivery with excellent properties such as low toxicity, reduced immunogenicity, good water solubility, and so forth. However, lack of understanding for the fate of PEG and PEGylated delivery systems at the cellular level has limited the application of PEGylated molecules in diagnosis and therapy. Here, we chose linear PEG 5k as a representative model and focused on the internalization behavior and mechanism, intracellular trafficking, sub-cellular localization, and cellular exocytosis of PEG and PEGylated molecules in living cells. Our investigation showed that PEG could be internalized into cells in 1 h. The internalized PEG was localized to lysosome, cytosol, endoplasmic reticulum (ER) and mitochondria. Importantly, the fate of PEG in cells could be regulated by conjugating different small molecules. PEGylated rhodamine B (PEG-RB) as the positively charged macromolecule was internalized into cells by micropinocytosis and then transported in lysosomes, ER, and mitochondria via vesicles sequentially. In contrast, PEGylated pyropheophorbide-a (PEG-PPa) as the negatively charged macromolecule was internalized into cells and transported to lysosomes ultimately. PEGylation slowed down the exocytosis process of RB and PPa and significantly prolonged their residence time inside the cells. These findings improve the understanding of how PEG and PEGylated molecules interact with the biological system at cellular and sub-cellular levels, which is of significance to rational PEGylation design for drug delivery.

Chlorophyllides: Preparation, Purification, and Application

Chlorophyllides can be found in photosynthetic organisms. Generally, chlorophyllides have a-, b-, c-, d-, and f-type derivatives, and all chlorophyllides have a tetrapyrrole structure with a Mg ion at the center and a fifth isocyclic pentanone. Chlorophyllide a can be synthesized from protochlorophyllide a, divinyl chlorophyllide a, or chlorophyll. In addition, chlorophyllide a can be transformed into chlorophyllide b, chlorophyllide d, or chlorophyllide f. Chlorophyllide c can be synthesized from protochlorophyllide a or divinyl protochlorophyllide a. Chlorophyllides have been extensively used in food, medicine, and pharmaceutical applications. Furthermore, chlorophyllides exhibit many biological activities, such as anti-growth, antimicrobial, antiviral, antipathogenic, and antiproliferative activity. The photosensitivity of chlorophyllides that is applied in mercury electrodes and sensors were discussed. This article is the first detailed review dedicated specifically to chlorophyllides. Thus, this review aims to describe the definition of chlorophyllides, biosynthetic routes of chlorophyllides, purification of chlorophyllides, and applications of chlorophyllides.

A Novel Allele Encoding 7-Hydroxymethyl Chlorophyll a Reductase Confers Bacterial Blight Resistance in Rice

Rice spotted leaf mutants are helpful to investigate programmed cell death (PCD) and defense response pathways in plants. Using a map-based cloning strategy, we characterized novel rice spotted leaf mutation spl^HM143 that encodes a 7-hydroxymethyl chlorophyll a reductase (OsHCAR). The wild-type (WT) allele could rescue the mutant phenotype, as evidenced by complementation analysis. OsHCAR was constitutively expressed at all rice tissues tested and its expression products localized to chloroplasts. The mutant exhibited PCD and leaf senescence with increased H₂O₂ (hydrogen peroxide) accumulation, increased of ROS (reactive oxygen species) scavenging enzymes activities and TUNEL (terminal deoxyribonucleotidyl transferase-mediated dUTP nick-end labeling) -positive nuclei, upregulation of PCD related genes, decreased chlorophyll (Chl) contents, downregulation of photosynthesis-related genes, and upregulation of senescence-associated genes. Besides, the mutant exhibited enhanced bacterial blight resistance with significant upregulation of defense response genes. Knockout lines of OsHCAR exhibited spotted leaf phenotype, cell death, leaf senescence, and showed increased resistance to the bacterial pathogen Xanthomonas oryzae pv. oryzae (Xoo) coupled with upregulation of five pathogenesis-related marker genes. The overexpression of OsHCAR resulted in increased susceptibility to Xoo with decreased expression of pathogenesis-related marker genes. Altogether, our findings revealed that OsHCAR is involved in regulating cell death and defense response against bacterial blight pathogen in rice.

Light-adapted charge-separated state of photosystem II: structural and functional dynamics of the closed reaction center

Photosystem II (PSII) uses solar energy to oxidize water and delivers electrons for life on Earth. The photochemical reaction center of PSII is known to possess two stationary states. In the open state (PSIIO), the absorption of a single photon triggers electron-transfer steps, which convert PSII into the charge-separated closed state (PSIIC). Here, by using steady-state and time-resolved spectroscopic techniques on Spinacia oleracea and Thermosynechococcus vulcanus preparations, we show that additional illumination gradually transforms PSIIC into a light-adapted charge-separated state (PSIIL). The PSIIC-to-PSIIL transition, observed at all temperatures between 80 and 308 K, is responsible for a large part of the variable chlorophyll-a fluorescence (Fv) and is associated with subtle, dark-reversible reorganizations in the core complexes, protein conformational changes at noncryogenic temperatures, and marked variations in the rates of photochemical and photophysical reactions. The build-up of PSIIL requires a series of light-induced events generating rapidly recombining primary radical pairs, spaced by sufficient waiting times between these events-pointing to the roles of local electric-field transients and dielectric relaxation processes. We show that the maximum fluorescence level, Fm, is associated with PSIIL rather than with PSIIC, and thus the Fv/Fm parameter cannot be equated with the quantum efficiency of PSII photochemistry. Our findings resolve the controversies and explain the peculiar features of chlorophyll-a fluorescence kinetics, a tool to monitor the functional activity and the structural-functional plasticity of PSII in different wild-types and mutant organisms and under stress conditions.

Comparative transcriptome analysis identifies genes associated with chlorophyll levels and reveals photosynthesis in green flesh of radish taproot

The flesh of the taproot of Raphanus sativus L. is rich in chlorophyll (Chl) throughout the developmental process, which is why the flesh is green. However, little is known about which genes are associated with Chl accumulation in this non-foliar, internal green tissue and whether the green flesh can perform photosynthesis. To determine these aspects, we measured the Chl content, examined Chl fluorescence, and carried out comparative transcriptome analyses of taproot flesh between green-fleshed "Cuishuai" and white-fleshed "Zhedachang" across five developmental stages. Numerous genes involved in the Chl metabolic pathway were identified. It was found that Chl accumulation in radish green flesh may be due to the low expression of Chl degradation genes and high expression of Chl biosynthesis genes, especially those associated with Part Ⅳ (from Protoporphyrin Ⅸ to Chl a). Bioinformatics analysis revealed that differentially expressed genes between "Cuishuai" and "Zhedachang" were significantly enriched in photosynthesis-related pathways, such as photosynthesis, antenna proteins, porphyrin and Chl metabolism, carbon fixation, and photorespiration. Twenty-five genes involved in the Calvin cycle were highly expressed in "Cuishuai". These findings suggested that photosynthesis occurred in the radish green flesh, which was also supported by the results of Chl fluorescence. Our study provides transcriptome data on radish taproots and provides new information on the formation and function of radish green flesh.

Estimating leaf photosynthesis of C3 plants grown under different environments from pigment index, photochemical reflectance index, and chlorophyll fluorescence

Photosynthetic rates vary depending on growth conditions, even within species. Remote sensing techniques have a great potential to predict the photosynthetic rates of leaves with different characteristics. Here, we demonstrate that the photosynthetic rates of leaves acclimated to different light and nutrient conditions can be estimated based on the chlorophyll fluorescence (ChlF), the photochemical reflectance index (PRI), and a chlorophyll index. Chenopodium album plants were grown under different light and nutrient conditions. PRI, ChlF parameters, and CO₂/H₂O gas exchange rates of leaves were simultaneously determined under the various light and CO₂ conditions. PRI was used to assess non-photochemical quenching (NPQ), but the relationship between NPQ and PRI was weakened when the data on leaves grown under different conditions were pooled, because PRI in darkness ([Formula: see text]) changed with the leaf pigment composition. Among 15 pigment indices, we found that [Formula: see text], a reflectance index related to the leaf chlorophyll content, had the best correlation with [Formula: see text] ([Formula: see text]) across the studied leaves, and the correction of PRI by [Formula: see text] improved the predictability of NPQ ([Formula: see text]). Using the steady-state ChlF, the NPQ estimated from PRI and [Formula: see text], and the stomatal conductance coefficient, we calculated the CO₂ assimilation rates, which were strongly correlated with the actual rates (RMSE = 4.85 [Formula: see text]mol m[Formula: see text] s[Formula: see text]), irrespective of growth conditions. Our approach has the potential to contribute to a more accurate estimation of photosynthetic rates in remote sensing. However, further studies on species variations and connecting with radiative transfer models are needed to demonstrate this at the canopy scale.

Self-assembled polymeric micelles for targeted photodynamic therapy of human epidermal growth factor receptor 2 overexpressing breast cancer

Photodynamic therapy (PDT) has been extensively explored as a promising alternative therapeutic approach for many malignant tumors. However, the PDT system generally involves unsatisfactory tumor specificity and nonspecific accumulation of photosensitizers around the target cancer cells, leading to phototoxic damage to adjacent healthy normal cells. In this study, we developed pheophorbide a (Pheo a)/human epidermal growth factor receptor 2 (HER2) targeting peptide (epitope form, HLTV, PEG2-LTVSPWY)-co-conjugated methoxy poly(ethylene glycol)-block-poly(L-lysine hydrochloride) (PEG-PLL)/hyaluronic acid (HA) (P3H2) polymeric micelles via a self-assembly method for HER2-targeted PDT treatment for breast cancer, thereby enhancing the PDT efficacy. The synthesized P3H2 polymeric micelles were spherical, with an average diameter of 125.7 ± 21.2 nm in an aqueous solution. The results ofin vitrocytotoxicity assays demonstrated that the P3H2 polymeric micelles significantly improved PDT efficacy on the SK-BR-3 cells due to the enhanced targeting ability. In addition, PDT treatment using the P3H2 polymeric micelles effectively killed breast cancer cells by inducing higher intracellular reactive oxygen species generation and apoptotic cell death. In particular, the three-dimensional cell culture model proved the synergistic PDT efficacy using P3H2 polymeric micelles on the SK-BR-3 cells. Based on these results, the PDT treatment using P3H2 polymeric micelles can serve as a highly effective therapeutic modality for breast cancer.

Using porphyrins as albumin-binding molecules to enhance antitumor efficacies and reduce systemic toxicities of antimicrobial peptides

Antimicrobial peptides (AMPs) are originally developed for anti-infective treatments. Because of their membrane-lytic property, AMPs have been considered as candidates of antitumor agents for a long time. However, their antitumor applications are mainly hampered by fast renal clearance and high systemic toxicities. This study proposes a strategy aiming at addressing these two issues by conjugating AMPs with porphyrins, which bind to albumin increasing AMPs' resistance against renal clearance and thus enhancing their antitumor efficacies. Porphyrins' photodynamic properties can further augment AMPs' antitumor effects. In addition, circulating with albumin ameliorates AMPs' systemic toxicities, i.e. hemolysis and organ dysfunctions. As an example, we conjugated an AMP, K6L9, with pyropheophorbide-a (PPA) leading to a conjugate of PPA-K6L9. PPA-K6L9 bound to albumin with a K_D value at the sub-micromolar range. Combining computational and experimental approaches, we characterized the molecular interaction of PPA-K6L9 with albumin. Furthermore, PPA-conjugation promoted K6L9' antitumor effects by prolonging its in vivo retention time, and reduced the hemolysis and hepatic injuries, which confirmed our design strategy.

Optimized Combination of Photodynamic Therapy and Chemotherapy Using Gelatin Nanoparticles Containing Tirapazamine and Pheophorbide a

In combination therapy, synergetic effects of drugs and their efficient delivery are essential. Herein, we screened 12 anticancer drugs for combination with photodynamic therapy (PDT) using pheophorbide a (Pba). On the basis of combination index (CI) values in cell viability tests, we selected tirapazamine (TPZ) and developed self-assembled gelatin nanoparticles (NPs) containing both Pba and TPZ. The resulting TPZ-Pba-NPs showed a synergetic effect to kill tumor cells because TPZ was activated under the hypoxic conditions that originated from the PDT with Pba and laser irradiation. After they were injected into tumor-bearing mice via the tail vein, TPZ-Pba-NPs showed 3.17-fold higher blood concentration and 4.12-fold higher accumulation in tumor tissue 3 and 24 h postinjection, respectively. Upon laser irradiation to tumor tissue, TPZ-Pba-NPs successfully suppressed tumor growth by efficient drug delivery and synergetic effects in vivo. These overall results suggest that in vitro screening of drugs based on CI values, mechanism studies in hypoxia, and real-time in vivo imaging are promising strategies in developing NPs for optimized combination therapy.

Characterization of a novel allele encoding pheophorbide a oxygenase in rice

We identified a rapid cell death 2 (rcd2) mutant from an indica cultivar Zhongjian100 mutant bank. The red-brown lesions appeared firstly on young seedling leaves, then gradually merged and the leaves completely withered at the late tillering stage. rcd2 displayed apparent cell death at/around the lesions, accumulation of superoxide anion (O₂^-) and disturbed ROS scavenging system, impaired photosynthetic capacity with significantly reduced chlorophyll content. The lesion formation was controlled by a single recessive nuclear gene and induced by natural light as well as mechanical wounding. A single base mutation (A1726T) at the 6th exon of OsMH_03G0040800 resulted in I576F substitution in the encoding protein, pheophorbide a oxygenase (PAO). Functional complementation could rescue the mutant phenotype and PAO-knockout lines exhibited the similar phenotype to rcd2. The activity of PAO decreased significantly while the content of PAO substrate, pheophorbide a, increased apparently in rcd2. The expression of chlorophyll synthesis/degradation-related genes and the contents of metabolic intermediates were largely changed. Furthermore, the level of chlorophyllide a, the product of chlorophyllase, increased significantly, indicating chlorophyllase might play a role in chlorophyll degradation in rice. Our results suggested that the I576F substitution disrupted PAO function, leading to O₂^- accumulation and chlorophyll degradation breakdown in rice.

Aptamer-Functionalized Upconverting Nanoformulations for Light-Switching Cancer-Specific Recognition and In Situ Photodynamic-Chemo Sequential Theranostics

Biomarker-activatable theranostic formulations offer the potential for removing specific tumors with a high diagnostic accuracy and a significant pharmacological effect. Herein, we developed a novel activatable theranostic nanoformulation UAS-PD [upconversion nanophosphor (UCNP)-aptamer/ssDNA-pyropheophorbide-a (PPA)-doxyrubicin (DOX)], which can recognize specific cancer cells with sensitivity and trigger the localized photodynamic destruction and enhanced chemotherapy. UAS-PD was constructed by the conjugation of UCNPs and aptamer probes containing the photosensitizer PPA and the chemotherapeutic drug DOX. When cancer cells are present, the UAS-PD specifically binds to PTK7, an overexpressed protein present on the surface of cancer cells, through conformational recombination of the aptamer structure and switches its upconversion luminescence from 655 to 540 nm. This long-lived ratiometric optical signal provides an ultrasensitive detection limit as low as 3.9 nM for PTK7. Changes in the conformation of UAS-PD can also induce PPA to approach UCNPs, which can produce cytotoxic singlet oxygens under near-infrared excitation to destroy the cell membrane and enhance its permeability for the simultaneously released DOX that targets cellular DNA degradation, which results in a highly effective tumor-killing effect by synergistic extra-intracellular sequential damage.

Effects of Ethanol Extracts from Grateloupia elliptica, a Red Seaweed, and Its Chlorophyll Derivative on 3T3-L1 Adipocytes: Suppression of Lipid Accumulation through Downregulation of Adipogenic Protein Expression

Grateloupia elliptica (G. elliptica) is a red seaweed with antioxidant, antidiabetic, anticancer, anti-inflammatory, and anticoagulant activities. However, the anti-obesity activity of G. elliptica has not been fully investigated. Therefore, the effect of G. elliptica ethanol extract on the suppression of intracellular lipid accumulation in 3T3-L1 cells by Oil Red O staining (ORO) was evaluated. Among the eight red seaweeds tested, G. elliptica 60% ethanol extract (GEE) exhibited the highest inhibition of lipid accumulation. GEE was the only extract to successfully suppress lipid accumulation among ethanol extracts from eight red seaweeds. In this study, we successfully isolated chlorophyll derivative (CD) from the ethyl acetate fraction (EA) of GEE by high-performance liquid chromatography and evaluated their inhibitory effect on intracellular lipid accumulation in 3T3-L1 adipocytes. CD significantly suppressed intracellular lipid accumulation. In addition, CD suppressed adipogenic protein expression such as sterol regulatory element-binding protein-1 (SREBP-1), peroxisome proliferator-activated receptor-γ (PPAR-γ), CCAAT/enhancer-binding protein-α (C/EBP-α), and fatty acid binding protein 4 (FABP4). Taken together, our results indicate that CD from GEE inhibits lipid accumulation by suppressing adipogenesis via the downregulation of adipogenic protein expressions in the differentiated adipocytes. Therefore, chlorophyll from G. elliptica has a beneficial effect on lipid metabolism and it could be utilized as a potential therapeutic agent for preventing obesity.

Laboratory-scale evaluation of algaecide effectiveness for control of microcystin-producing cyanobacteria from Lake Okeechobee, Florida (USA)

Growth of microcystin-producing cyanobacteria in Lake Okeechobee (Florida, USA) and surrounding waters has resulted in adverse health impacts for humans and endangered species, as well as significant economic losses. As these issues worsen, there is growing pressure for efficacious solutions to rapidly mitigate harmful algal blooms (HABs) and protect critical freshwater resources. Applications of USEPA-registered algaecides as management tactics meet many decision-making criteria often required by water resource managers (e.g., effective, scalable, selective), but have not yet been evaluated on a large scale within the Lake Okeechobee waterway. This study was conducted to bolster the peer-reviewed database for available management tactics against microcystin-producing cyanobacteria in waters of this region. Laboratory-scale experiments can be conducted first to minimize uncertainty at larger scales and improve confidence in decision-making. In this study, samples containing microcystin-producing cyanobacteria collected from Lake Okeechobee were exposed to several USEPA-registered algaecides in laboratory toxicity experiments. Responses of target cyanobacteria were measured 3 days after treatment (DAT) in terms of cell density, chlorophyll-a concentrations, and phycocyanin concentrations. Based on responses of the cyanobacteria, minimum effective exposure concentrations were identified for each algaecide. Microcystin release (i.e. proportion of total microcystins in the aqueous phase) was measured and compared 1 DAT among effective exposures. Total microcystin concentrations were measured in effective treatments at 1, 4, and 9 DAT to discern potential for microcystin persistence following exposures to the effective formulations and exposure concentrations. Overall, several formulations including GreenClean Liquid® 5.0, GreenClean Liquid® 5.0 combined with Hydrothol® 191, and the copper-based algaecides evaluated (Algimycin® PWF, Argos, Captain® XTR, Cutrine® Ultra, and SeClear®) achieved significant and similar effects on target cyanobacteria. The chelated copper-based formulations (Algimycin® PWF, Argos, Captain® XTR, and Cutrine® Ultra) resulted in relatively less microcystin release 1 DAT and lesser total microcystin concentrations 4 DAT. At 9 DAT, total microcystin concentrations were significantly lower than in untreated controls in all treatments evaluated. These results provide the necessary comparative performance data for preliminary decision-making and designing additional studies at larger scales. Importantly, the comparative toxicity data and approach provided in this study demonstrate the initial steps for development of site-specific management strategies for Lake Okeechobee and other areas impacted by harmful algal blooms with large spatial and temporal scales.

Sonodynamic therapy in combination with photodynamic therapy shows enhanced long-term cure of brain tumor

This article presents the construction of a multimodality platform that can be used for efficient destruction of brain tumor by a combination of photodynamic and sonodynamic therapy. For in vivo studies, U87 patient-derived xenograft tumors were implanted subcutaneously in SCID mice. For the first time, it has been shown that the cell-death mechanism by both treatment modalities follows two different pathways. For example, exposing the U87 cells after 24 h incubation with HPPH [3-(1'-hexyloxy)ethyl-3-devinyl-pyropheophorbide-a) by ultrasound participate in an electron-transfer process with the surrounding biological substrates to form radicals and radical ions (Type I reaction); whereas in photodynamic therapy, the tumor destruction is mainly caused by highly reactive singlet oxygen (Type II reaction). The combination of photodynamic therapy and sonodynamic therapy both in vitro and in vivo have shown an improved cell kill/tumor response, that could be attributed to an additive and/or synergetic effect(s). Our results also indicate that the delivery of the HPPH to tumors can further be enhanced by using cationic polyacrylamide nanoparticles as a delivery vehicle. Exposing the nano-formulation with ultrasound also triggered the release of photosensitizer. The combination of photodynamic therapy and sonodynamic therapy strongly affects tumor vasculature as determined by dynamic contrast enhanced imaging using HSA-Gd(III)DTPA.

HCAR Is a Limitation Factor for Chlorophyll Cycle and Chlorophyll b Degradation in Chlorophyll-b-Overproducing Plants

The chlorophyll (Chl) cycle is the metabolic pathway for Chl a and Chl b inter-conversion. In this pathway, Chl b is synthesized from Chl a by the catalyzing action of chlorophyllide a oxygenase (CAO). In contrast, Chl b is firstly reduced to produce 7-hydroxymethyl Chl (HMChl) a, which is catalyzed by two isozymes of Chl b reductase (CBR), non-yellow coloring 1 (NYC1) and NYC1-like (NOL). Subsequently, HMChl a is reduced to Chl a by HMChl a reductase (HCAR). CAO plays a pivotal role in Chl a/b ratio regulation and plants over-accumulate Chl b in CAO-overexpressing plants. NYC1 is more accumulated in Chl-b-overproducing plants, while HCAR is not changed. To investigate the role of HCAR in Chl cycle regulation, the Chl metabolites of Chl-b-overproducing plants were analyzed. The results showed that HMChl a accumulated in these plants, and it decreased and the Chl a/b ratio increased by overexpressing HCAR, implying HCAR is insufficient for Chl cycle in Chl-b-overproducing plants. Furthermore, during dark-induced senescence, the non-programmed cell death symptoms (leaves dehydrated with green color retained) of Chl-b-overproducing plants were obviously alleviated, and the content of HM pheophorbide (HMPheide) a and Pheide b were sharply decreased by overexpressing HCAR. These results imply that HCAR is also insufficient for Chl degradation in Chl-b-overproducing plants during senescence, thus causing the accumulation of Chl metabolites and non-programmed cell death of leaves. With these results taken together, we conclude that HCAR is not well regulated and it is a limiting factor for Chl cycle and Chl b degradation in Chl-b-overproducing plants.

Effects of CO2 and temperature on photosynthetic performance in the diatom Chaetoceros gracilis

CO₂ concentration and temperature for growth of photosynthetic organisms are two important factors to ensure better photosynthetic performance. In this study, we investigated the effects of CO₂ concentration and temperature on the photosynthetic performance in a marine centric diatom Chaetoceros gracilis. Cells were grown under four different conditions, namely, at 25 °C with air bubbling, at 25 °C with a supplementation of 3% CO₂, at 30 °C with air bubbling, and at 30 °C with the CO₂ supplementation. It was found that the growth rate of cells at 30 °C with the CO₂ supplementation is faster than those at other three conditions. The pigment compositions of cells grown under the different conditions are altered, and fluorescence spectra measured at 77 K also showed different peak positions. A novel fucoxanthin chlorophyll a/c-binding protein complex is observed in the cells grown at 30 °C with the CO₂ supplementation but not in the other three types of cells. Since oxygen-evolving activities of the four types of cells are almost unchanged, it is suggested that the CO₂ supplementation and growth temperature are involved in the regulation of photosynthetic light-harvesting apparatus in C. gracilis at different degrees. Based on these observations, we discuss the favorable growth conditions for C. gracilis.

Adaptation of light-harvesting and energy-transfer processes of a diatom Phaeodactylum tricornutum to different light qualities

Fucoxanthin-chlorophyll (Chl) a/c-binding proteins (FCPs) are light-harvesting pigment-protein complexes found in diatoms and brown algae. Due to the characteristic pigments, such as fucoxanthin and Chl c, FCPs can capture light energy in blue-to green regions. A pennate diatom Phaeodactylum tricornutum synthesizes a red-shifted form of FCP under weak or red light, extending a light-absorption ability to longer wavelengths. In the present study, we examined changes in light-harvesting and energy-transfer processes of P. tricornutum cells grown under white- and single-colored light-emitting diodes (LEDs). The red-shifted FCP appears in the cells grown under the green, yellow, and red LEDs, and exhibited a fluorescence peak around 714 nm. Additional energy-transfer pathways are established in the red-shifted FCP; two forms (F713 and F718) of low-energy Chl a work as energy traps at 77 K. Averaged fluorescence lifetimes are prolonged in the cells grown under the yellow and red LEDs, whereas they are shortened in the blue-LED-grown cells. Based on these results, we discussed the light-adaptation machinery of P. tricornutum cells involved in the red-shifted FCP.

Glycodendron/pyropheophorbide-a (Ppa)-functionalized hyaluronic acid as a nanosystem for tumor photodynamic therapy

To enhance the drug delivery efficiency of hyaluronic acid (HA), we designed and prepared glycodendron and pyropheophorbide-a (Ppa)-functionalized HA (HA-Ppa-Dendron) as a nanosystem for cancer photodynamic therapy. Linear Ppa-modified HA (HA-Ppa) was also prepared as a control. Cellular uptake of both polymers by MDA-MB-231 cells led to mitochondrial dysfunction and generation of reactive oxygen species under the irradiation of a laser. Compared to the linear polymer, HA-Ppa-Dendron had higher molecular weight, a more compact nanoscale particle size, and a dendritic structure, resulting in a much longer blood circulation time and higher tumor accumulation. HA-Ppa-Dendron outperformed HA-Ppa in inhibiting cell growth, with 60 % of tumors was eradicated under laser irradiation. Tumor growth inhibition (TGI) up to 99.2 % was achieved from HA-Ppa-Dendron, which was much higher than that of HA-Ppa (50.6 %). Therefore, glycodendron-functionalized HAs by integration of HA and dendritic polymers may act as efficient anti-cancer nanomedicine.

Transcriptome and cell wall degrading enzyme-related gene analysis of Pestalotiopsis neglecta in response to sodium pheophorbide a

Sodium pheophorbide a (SPA) is a new alternative fungicide with low toxicity and high efficiency, which has high fungicidal activity against Pestalotiopsis neglecta, a pathogen that causes black spot needle blight of Pinus sylvestris var. mongolica. To utilize SPA for plant disease control, understanding its antifungal mechanism is essential. Six cDNA libraries were constructed from 3 d-old P. neglecta mycelia (three SPA-infected and three untreated groups) and 29,850 expressed genes were obtained by Illumina HiSeq4000 sequencing. Compared with controls, 3268 differentially expressed genes (DEGs) were identified in SPA-treated groups, including 1879 upregulated and 1389 downregulated genes. Most DEGs were involved in the metabolism of amino acids, carbohydrates, and lipids, as well as cell structure and genetic information processing. These findings were further confirmed by decreased conductivity, RNA and protein content, and activities of nicotinamide adenine dinucleotide-dependent malate dehydrogenase, citrate synthase, isocitrate dehydrogenase, and succinate dehydrogenase. Moreover, qRT-PCR verified the reliability of the transcriptome results. After treatment with SPA at different concentrations for 60 min, the expressions of three cell wall degrading enzyme-related genes (PnEG, PnBG, and PnPG) were all suppressed. Overall, this study provided insights into the molecular mechanisms through which SPA inhibits P. neglecta, increasing the possibility of developing SPA into an effective fungicide in the future.

Water conservancy project on the Yellow River modifies the seasonal variation of Chlorophyll-a in the Bohai Sea

The Water Sediment Regulation Scheme (WSRS) is a unique engineering measure that has been regularly performed to reduce reservoir sedimentation and increase the flood capacity of the Yellow River in China since 2002. As a side effect, the WSRS greatly increases the monthly input flux of nutrients to the Bohai Sea (BHS) in summer, potentially exacerbating eutrophication levels therein and subsequently affecting the growth of phytoplankton. However, its influence on the Chlorophyll-a (Chl-a) dynamics over the BHS is still poorly understood. In this study, two approaches were adopted to investigate it: 1) long-term in-situ observations and satellite-derived data of surface Chl-a were used to study its seasonal variations before and since 2002, and 2) one 1D physical-biological coupled model was developed to evaluate the impact of WSRS on seasonal Chl-a. The results showed that the surface Chl-a exhibited two peaks in spring and autumn until 2002, but has exhibited only one peak in spring-summer since 2002. Satellite-derived Chl-a concentrations in spring-summer since 2002 have increased by 56% compared to those until 2002. The simulated results showed that the change in Yellow River discharge induced by the WSRS has resulted in the appearance of high concentrations of Chl-a in summer over the Central Bohai Sea since 2002. The WSRS increased the ratio of added Chl-a owing to the riverine nutrients to total Chl-a by 19% compared to that until 2002. Overall, WSRS greatly affects the seasonal cycling of Chl-a in the Bohai Sea, and the side effect needs to be considered.

Far-red absorption and light-use efficiency trade-offs in chlorophyll f photosynthesis

Plants and cyanobacteria use the chlorophylls embedded in their photosystems to absorb photons and perform charge separation, the first step of converting solar energy to chemical energy. While oxygenic photosynthesis is primarily based on chlorophyll a photochemistry, which is powered by red light, a few cyanobacterial species can harness less energetic photons when growing in far-red light. Acclimatization to far-red light involves the incorporation of a small number of molecules of red-shifted chlorophyll f in the photosystems, whereas the most abundant pigment remains chlorophyll a. Due to its different energetics, chlorophyll f is expected to alter the excited-state dynamics of the photosynthetic units and, ultimately, their performances. Here we combined time-resolved fluorescence measurements on intact cells and isolated complexes to show that chlorophyll f insertion slows down the overall energy trapping in both photosystems. While this marginally affects the efficiency of photosystem I, it substantially decreases that of photosystem II. Nevertheless, we show that despite the lower energy output, the insertion of red-shifted chlorophylls in the photosystems remains advantageous in environments that are enriched in far-red light and therefore represents a viable strategy for extending the photosynthetically active spectrum in other organisms, including plants. However, careful design of the new photosynthetic units will be required to preserve their efficiency.

The diversity and distribution of D1 proteins in cyanobacteria

The psbA gene family in cyanobacteria encodes different forms of the D1 protein that is part of the Photosystem II reaction centre. We have identified a phylogenetically distinct D1 group that is intermediate between previously identified G3-D1 and G4-D1 proteins (Cardona et al. Mol Biol Evol 32:1310-1328, 2015). This new group contained two subgroups: D1^INT, which was frequently in the genomes of heterocystous cyanobacteria and D1^FR that was part of the far-red light photoacclimation gene cluster of cyanobacteria. In addition, we have identified subgroups within G3, the micro-aerobically expressed D1 protein. There are amino acid changes associated with each of the subgroups that might affect the function of Photosystem II. We show a phylogenetically broad range of cyanobacteria have these D1 types, as well as the genes encoding the G2 protein and chlorophyll f synthase. We suggest identification of additional D1 isoforms and the presence of multiple D1 isoforms in phylogenetically diverse cyanobacteria supports the role of these proteins in conferring a selective advantage under specific conditions.

Growth model of chlorosome antenna by the environment-dependent stepwise assembly of a zinc chlorophyll derivative

A zinc chlorophyll derivative possessing an oligoethylene glycol ester at the 17-propionate residue was prepared as a model of specific pigments in chlorosomes, such as bacteriochlorophylls-c, d, and e, by chemical modification of naturally occurring chlorophyll-a. The zinc chlorophyll derivative aggregated in aqueous or hexane solutions containing 1% (v/v) ethanol to give red-shifted and broadened Soret/Qy absorption bands with intense circular dichroism signals, indicating the formation of its chlorosome-like J-type self-aggregates. The atomic force microscope images of the self-aggregates prepared in aqueous or hexane solutions showed thin tube-like (ca. 3 nm diameter) or thick rod-like aggregates (> 20 nm diameter), respectively. After standing these solutions for several days, the nanotubes or nanorods further assembled to give ribbon- or bundle-like aggregates, respectively. The latter transformation (tube to ribbon) was triggered by hydrogen bonding between oligoethylene glycol esters located outside of the tubes via water or ethanol molecules. These dynamic supramolecular transformations may also be useful for revealing the growth process of bacteriochlorophyll self-aggregates in a chlorosome.

Key factors affecting photoactivated fungicidal activity of sodium pheophorbide a against Pestalotiopsis neglecta

Recently, photodynamic therapy (PDT) and photoactivated pesticides have attracted considerable research attention. In the present study, we aimed to investigate the photodynamic activity of a chlorophyllous derivative, sodium pheophorbide a (SPA), and to evaluate its potential as a photoactivated fungicide. The singlet oxygen quantum yield, the photoreaction process, the anti-photobleaching ability in sterile water (H₂O), the effect of light conditions on its antifungal activity, and its stability were all investigated. SPA showed significant fungicidal activity and photostability, during which Type I and Type II photodynamic reactions occurred simultaneously on Pestalotiopsis neglecta, and the influence of Type I was slightly larger than that of Type II. In addition, light promoted the antifungal activity of SPA. In particular, the antifungal activity was enhanced with increasing light intensity, and was strongest under 8000 lx conditions. Under monochromatic light sources, antifungal activity was strongest under green light s; however, the effect of monochromatic light was not as good as that of white light. From 0 to 24 h, the antifungal effect of the SPA solution was enhanced; however, the activity of the solution began to weaken after 24 h. Furthermore, our study confirmed that the antifungal activity of SPA was stable under different temperatures, pH values, and UV irradiation durations.

Self-Quenched Polysaccharide Nanoparticles with a Reactive Oxygen Species-Sensitive Cascade for Enhanced Photodynamic Therapy

Tumor microenvironment (TME)-responsive nanocarrier systems that keep the photosensitizer (PS) inactive during systemic circulation and then efficiently release or activate the PS in response to unique TME conditions have attracted much attention. Herein, we report novel TME-responsive, self-quenched polysaccharide nanoparticles (NPs) with a reactive oxygen species (ROS)-sensitive cascade. The PS, pheophorbide A (PhA), was conjugated to a water-soluble glycol chitosan (GC) through an ROS-sensitive thioketal (TK) linker. The amphiphilic GC-TK-PhA conjugates could arrange themselves into NPs and remain photoinactive due to their self-quenching effects. Upon reaching the ROS-rich hypoxic core of the tumor tissue, the NPs release the PS in a photoactive form by efficient, ROS-sensitive TK bond cleavage, thus generating potent phototoxic effects. Following near-infrared irradiation, the increase in locoregional ROS levels further accelerates the release and activation of PS. These cascade reactions caused a significant reduction in the tumor volume, demonstrating good antitumor potential.

Safflower (Carthamus tinctorius) Biochemical Properties, Yield, and Oil Content Affected by 24-Epibrassinosteroid and Genotype under Drought Stress

The steroid hormones, including brassinosteroids, regulate plant growth under stress. It is hypothesized that 24-epibrassinosteroids (24-EBR) can affect safflower (Carthamus tinctorius) biochemical properties, crop yield, and oil content under drought stress. The objective of our study was to determine the response of three safflower genotypes (Goldasht, Faraman, and Sina) to exogenous 24-EBR (0 and 10^-7 M) under drought stress, including 85, 65, and 45% of field capacity in 2015. Stress decreased chlorophyll-a, chlorophyll-b, total chlorophyll, carotenoid, relative water content (RWC), seed yield, and oil percentage. The activities of superoxide dismutase (SOD), catalase (CAT), polyphenol oxidase (PPO), and proline contents increased in response to either drought stress or 24-EBR. Genotypes behaved significantly different under stress. 24-EBR significantly increased plant chlorophyll contents and oil percentage, and it significantly reduced the malondialdehyde (MDA) content via increasing the proline and carotenoid contents under stress. 24-EBR can increase safflower oil and seed yield under drought stress.

Sodium pheophorbide a controls cherry tomato gray mold (Botrytis cinerea) by destroying fungal cell structure and enhancing disease resistance-related enzyme activities in fruit

Sodium pheophorbide a (SPA) is a natural photosensitizer. The present study investigated the antifungal activity and mechanism of SPA against Botrytis cinerea in vitro and in vivo. Its inhibitory effect was studied on the spore germination and mycelial growth of B. cinerea. The effects of SPA on cell wall integrity, cell membrane permeability, and mycelial morphology of B. cinerea were also determined. Additionally, how SPA effected B. cinerea in vivo was evaluated using cherry tomato fruit. The results showed that SPA effectively inhibited the spore germination and mycelial growth of B. cinerea under light conditions (4000 lx). SPA significantly affected both cell wall integrity and cell membrane permeability (P < .05). In addition, SEM analysis suggested that B. cinerea treated with SPA (12.134 mg/mL) showed abnormal mycelial morphology, including atrophy, collapse, flattening, and mycelial wall dissolution. In vivo tests showed that SPA could increase the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) significantly (P < .05); however, SPA had no significant effect on phenylalanine ammonia lyase (PAL) activity. In short, SPA could destroy the fungal cell structure and enhance disease resistance-related enzyme activity in cherry tomatoes, thereby controlling cherry tomato gray mold.

The pigment binding behaviour of water-soluble chlorophyll protein (WSCP)

Water-soluble chlorophyll proteins (WSCPs) are homotetrameric proteins that bind four chlorophyll (Chl) molecules in identical binding sites, which makes WSCPs a good model to study protein-pigment interactions. In a previous study, we described preferential binding of Chl a or Chl b in various WSCP versions. Chl b binding is preferred when a hydrogen bond can be formed between the C7 formyl of the chlorin macrocycle and the protein, whereas Chl a is preferred when Chl b binding is sterically unfavorable. Here, we determined the binding affinities and kinetics of various WSCP versions not only for Chl a/b, but also for chlorophyllide (Chlide) a/b and pheophytin (Pheo) a/b. Altered KD values are responsible for the Chl a/b selectivity in WSCP whereas differences in the reaction kinetics are neglectable in explaining different Chl a/b preferences. WSCP binds both Chlide and Pheo with a lower affinity than Chl, which indicates the importance of the phytol chain and the central Mg2+ ion as interaction sites between WSCP and pigment. Pheophorbide (Pheoide), lacking both the phytol chain and the central Mg2+ ion, can only be bound as Pheoide b to a WSCP that has a higher affinity for Chl b than Chl a, which underlines the impact of the C7 formyl-protein interaction. Moreover, WSCP was able to bind protochlorophyllide and Mg-protoporphyrin IX, which suggests that neither the size of the π electron system of the macrocycle nor the presence of a fifth ring at the macrocycle notably affect the binding to WSCP. WSCP also binds heme to form a tetrameric complex, suggesting that heme is bound in the Chl-binding site.

Pluronic F-127: An Efficient Delivery Vehicle for 3-(1'-hexyloxy)ethyl-3-devinylpyropheophorbide-a (HPPH or Photochlor)

To determine the impact of delivery vehicles in photosensitizing efficacy of HPPH, a hydrophobic photosensitizer was dissolved in various formulations: 1% Tween 80/5% dextrose, Pluronic P-123 and Pluronic F-127 in 0.5%, 1% and 2% phosphate buffer solutions (PBS). HPPH was also conjugated to Pluronic F-127, and the resulting conjugate (PL-20) was formulated in PBS. Among the different delivery vehicles, only Pluronic P-123 displayed significant vehicle cytotoxicity, whereas Pluronic F127 was nontoxic. Compared to PL-20, HPPH formulated in Tween80 and Pluronic F-127 showed higher cell-uptake, but lower long-term retention in Colon26 cell compared to PL-20. The higher retention of PL-20 was similarly observed during in vivo uptake with BALB/c mice baring Ct26 tumors. In contrast to the in vitro uptake experiments, PL-20 showed slightly higher uptake compared to HPPH formulated in Tween or Pluronic-F127. A significant difference in pharmacokinetic profile was also observed between the HPPH-Pluronic formulation and PL-20. Under similar in vivo treatment parameters (drug dose 0.47 µmol kg^-1 , light dose: 135 J cm^-2 at 24 h post-injection of PS), HPPH formulated either in Tween or Pluronic F-127 formulation showed similar in vivo PDT efficacy (20-30% tumor cure on day 60), whereas PL-20 showed 40% tumor cure (day 60).

Employing bicontinuous-to-micellar transitions in nanostructure morphology for on-demand photo-oxidation responsive cytosolic delivery and off-on cytotoxicity

Bicontinuous nanospheres (BCNs) are underutilized self-assembled nanostructures capable of simultaneous delivery of both hydrophilic and hydrophobic payloads. Here, we demonstrate that BCNs assembled from poly(ethylene glycol)-block-poly(propylene sulfide) (PEG-b-PPS), an oxidation-sensitive copolymer, are stably retained within cell lysosomes following endocytosis, resisting degradation and payload release for days until externally triggered. The oxygen scavenging properties and enhanced stability of the bicontinuous PEG-b-PPS nanoarchitecture significantly protected cells from typically cytotoxic application of pro-apoptotic photo-oxidizer pheophorbide A and chemotherapeutic camptothecin. The photo-oxidation triggered transition from a bicontinuous to micellar morphology overcame this stability, allowing on-demand cytosolic delivery of camptothecin for enhanced control over off-on cytotoxicity. These results indicate that inducible transitions in the nanostructure morphology can influence intracellular stability and toxicity of self-assembled nanotherapeutics.

Chlorophyll f synthesis by a super-rogue photosystem II complex

Certain cyanobacteria synthesize chlorophyll molecules (Chl d and Chl f) that absorb in the far-red region of the solar spectrum, thereby extending the spectral range of photosynthetically active radiation^1,2. The synthesis and introduction of these far-red chlorophylls into the photosynthetic apparatus of plants might improve the efficiency of oxygenic photosynthesis, especially in far-red enriched environments, such as in the lower regions of the canopy³. Production of Chl f requires the ChlF subunit, also known as PsbA4 (ref. ⁴) or super-rogue D1 (ref. ⁵), a paralogue of the D1 subunit of photosystem II (PSII) which, together with D2, bind cofactors involved in the light-driven oxidation of water. Current ideas suggest that ChlF oxidizes Chl a to Chl f in a homodimeric ChlF reaction centre (RC) complex and represents a missing link in the evolution of the heterodimeric D1/D2 RC of PSII (refs. ^4,6). However, unambiguous biochemical support for this proposal is lacking. Here, we show that ChlF can substitute for D1 to form modified PSII complexes capable of producing Chl f. Remarkably, mutation of just two residues in D1 converts oxygen-evolving PSII into a Chl f synthase. Overall, we have identified a new class of PSII complex, which we term 'super-rogue' PSII, with an unexpected role in pigment biosynthesis rather than water oxidation.

Self-Amplified Photodynamic Therapy through the 1 O2 -Mediated Internalization of Photosensitizers from a Ppa-Bearing Block Copolymer

Nanocarriers are employed to deliver photosensitizers for photodynamic therapy (PDT) through the enhanced penetration and retention effect, but disadvantages including the premature leakage and non-selective release of photosensitizers still exist. Herein, we report a 1 O2 -responsive block copolymer (POEGMA-b-P(MAA-co-VSPpaMA) to enhance PDT via the controllable release of photosensitizers. Once nanoparticles formed by the block copolymer have accumulated in a tumor and have been taken up by cancer cells, pyropheophorbide a (Ppa) could be controllably released by singlet oxygen (1 O2 ) generated by light irradiation, enhancing the photosensitization. This was demonstrated by confocal laser scanning microscopy and in vivo fluorescence imaging. The 1 O2 -responsiveness of POEGMA-b-P(MAA-co-VSPpaMA) block copolymer enabled the realization of self-amplified photodynamic therapy by the regulation of Ppa release using NIR illumination. This may provide a new insight into the design of precise PDT.

Typhoon Merbok induced upwelling impact on material transport in the coastal northern South China Sea

Typhoons frequently affect the South China Sea (SCS), playing an important role in changing the coastal marine system. To determine which process has the greatest impact on material transport in the coastal marine area during a typhoon, the sea temperature, salinity, concentration of nutrients, chlorophyll-a, total suspended matter, and δ¹³C of particulate organic carbon (δ¹³C-POC) in the water column of coastal Northern SCS (NSCS) were measured during two cruises in June 2017, in the pre- and post-typhoon Merbok periods. The results show that all parameters changed significantly between the two periods. During the pre-typhoon period, stratification of nutrients and physicochemical parameters, combined to high nutrient concentrations, high temperature, and low salinity in the water column of the nearshore area, suggests that the nearshore area is influenced by the river diluted water originated in the coastal cities adjacent to our study area. In the offshore area, mineralization may be responsible for the high nutrient concentration in the bottom water. However, during the post-typhoon, the stratification of nutrients is less significant and their distribution more homogenous in the whole water column of the nearshore area. In the upper water, the nutrient concentration increased and the temperature decreased significantly. These results suggest that the enhanced vertical mixing induced by the typhoon was the dominant process in changing the nutrient distribution pattern in the coastal NSCS.

Pheophorbide a May Regulate Jasmonate Signaling during Dark-Induced Senescence

Chlorophyll degradation is one of the most visible signs of leaf senescence. During senescence, chlorophyll is degraded in the multistep pheophorbide a oxygenase (PAO)/phyllobilin pathway. This pathway is tightly regulated at the transcriptional level, allowing coordinated and efficient remobilization of nitrogen toward sink organs. Using a combination of transcriptome and metabolite analyses during dark-induced senescence of Arabidopsis (Arabidopsis thaliana) mutants deficient in key steps of the PAO/phyllobilin pathway, we show an unanticipated role for one of the pathway intermediates, i.e. pheophorbide a Both jasmonic acid-related gene expression and jasmonic acid precursors specifically accumulated in pao1, a mutant deficient in PAO. We propose that pheophorbide a, the last intact porphyrin intermediate of chlorophyll degradation and a unique pathway "bottleneck," has been recruited as a signaling molecule of chloroplast metabolic status. Our work challenges the assumption that chlorophyll breakdown is merely a result of senescence, and proposes that the flux of pheophorbide a through the pathway acts in a feed-forward loop that remodels the nuclear transcriptome and controls the pace of chlorophyll degradation in senescing leaves.

Disruption of the Unique ABCG-Family NBD:NBD Interface Impacts Both Drug Transport and ATP Hydrolysis

ABCG2 is one of a triumvirate of human multidrug ATP binding cassette (ABC) transporters that are implicated in the defense of cells and tissues against cytotoxic chemicals, but these transporters can also confer chemotherapy resistance states in oncology. Understanding the mechanism of ABCG2 is thus imperative if we are to be able to counter its deleterious activity. The structure of ABCG2 and its related family members (ABCG5/G8) demonstrated that there were two interfaces between the nucleotide binding domains (NBD). In addition to the canonical ATP “sandwich-dimer” interface, there was a second contact region between residues at the C-terminus of the NBD. We investigated this second interface by making mutations to a series of residues that are in close interaction with the opposite NBD. Mutated ABCG2 isoforms were expressed in human embryonic kidney (HEK) 293T cells and analysed for targeting to the membrane, drug transport, and ATPase activity. Mutations to this second interface had a number of effects on ABCG2, including altered drug specificity, altered drug transport, and, in two mutants, a loss of ATPase activity. The results demonstrate that this region is particularly sensitive to mutation and can impact not only direct, local NBD events (i.e., ATP hydrolysis) but also the allosteric communication to the transmembrane domains and drug transport.

Far-red light allophycocyanin subunits play a role in chlorophyll d accumulation in far-red light

Some terrestrial cyanobacteria acclimate to and utilize far-red light (FRL; λ = 700-800 nm) for oxygenic photosynthesis, a process known as far-red light photoacclimation (FaRLiP). A conserved, 20-gene FaRLiP cluster encodes core subunits of Photosystem I (PSI) and Photosystem II (PSII), five phycobiliprotein subunits of FRL-bicylindrical cores, and enzymes for synthesis of chlorophyll (Chl) f and possibly Chl d. Deletion mutants for each of the five apc genes of the FaRLiP cluster were constructed in Synechococcus sp. PCC 7335, and all had similar phenotypes. When the mutants were grown in white (WL) or red (RL) light, the cells closely resembled the wild-type (WT) strain grown under the same conditions. However, the WT and mutant strains were very different when grown under FRL. Mutants grown in FRL were unable to assemble FRL-bicylindrical cores, were essentially devoid of FRL-specific phycobiliproteins, but retained RL-type phycobilisomes and WL-PSII. The transcript levels for genes of the FaRLiP cluster in the mutants were similar to those in WT. Surprisingly, the Chl d contents of the mutant strains were greatly reduced (~ 60-99%) compared to WT and so were the levels of FRL-PSII. We infer that Chl d may be essential for the assembly of FRL-PSII, which does not accumulate to normal levels in the mutants. We further infer that the cysteine-rich subunits of FRL allophycocyanin may either directly participate in the synthesis of Chl d or that FRL bicylindrical cores stabilize FRL-PSII to prevent loss of Chl d.

Combined toxic effects of microcystin-LR and phenanthrene on growth and antioxidant system of duckweed (Lemna gibba L.)

Microcystins and polycyclic aromatic hydrocarbons commonly co-exist in eutrophic freshwater environments. However, their combined toxicity remains unknown. The aim of this study was to evaluate the combined toxic effects of microcystin-LR (MC-LR) and phenanthrene (Phe) on duckweed (Lemna gibba L.) during a short-term exposure (7 d). L. gibba was exposed to a range of environmentally relevant concentrations of MC-LR (5, 50, 250, 500 μg/L) and Phe (0.1, 1, 5, 10 μg/L), both individually and in MC-LR + Phe mixtures (5 + 0.1, 50 + 1, 250 + 5, 500 + 10 μg/L). Subsequently, biomarkers of toxicity such as growth, chlorophyll-a, and antioxidant enzyme activity (catalase, superoxide dismutase, and peroxidase) were analyzed in L. gibba. Growth and the antioxidant system of L. gibba were not significantly inhibited by Phe alone, whereas higher concentrations of individual MC-LR (≥50 μg/L) significantly inhibited growth and induced oxidative stress. Based on Abott's formula, their interaction effects were concentration dependent. Antagonistic effects were observed when exposed to combinations of lower concentrations of MC-LR and Phe (≤50 + 1 μg/L), while additive or synergistic effects were induced at higher concentrations of both compounds (≥250 + 5 μg/L). Moreover, higher concentrations of Phe (≥5 μg/L) increased the accumulation of MC-LR in L. gibba. Our results suggested that the toxic effects of MC-LR and phenanthrene were exacerbated only when they co-exist in water bodies at relatively high concentrations. Consequently, co-existence of MC-LR and Phe at low levels are unlikely to exacerbate ecological hazards to L. gibba in most aquatic environments, at least based on responses of this plant.

Winter climate change increases physiological stress in calcareous fen bryophytes

Calcareous spring fens are among the rarest and most endangered wetland types worldwide. The majority of these ecosystems can be found at high latitudes, where they are affected by above average rates of climate change. Particularly winter temperatures are increasing, which results in decreased snow cover. As snow provides an insulating layer that protects ecosystems from subzero temperatures, its decrease is likely to induce stress to plants. To investigate the sensitivity of the bryophyte community - key to the functioning of calcareous spring fens - to changing climatic conditions, we studied the annual variation in ecophysiology of two dominant bryophytes: Campylium stellatum and Scorpidium scorpioides. Further, a snow removal experiment was used to simulate the effect of changing winter conditions. In both species, we observed lowest efficiency of photosystem II (Fv/Fm) in spring, indicating physiological stress, and highest chlorophyll-a, -b and carotenoid concentrations in autumn. Snow removal exacerbated physiological stress in bryophytes. Consequently Fv/Fm, pigment concentrations and chlorophyll to carotenoids ratios declined, while chlorophyll-a to -b ratios increased. Moreover, these effects of winter climate change cascaded to the growing season. C. stellatum, a low hummock inhabitor, suffered more from snow removal (annual mean decline in Fv/Fm 7.7% and 30.0% in chlorophyll-a) than S. scorpioides, a hollow species (declines 5.4% and 14.5%, respectively). Taken together, our results indicate that spring fen bryophytes are negatively impacted by winter climate change, as a result of longer frost periods and increased numbers of freeze-thaw cycles in combination with higher light intensity and dehydration.

Açaí palm seedling growth promotion by rhizobacteria inoculation

Lower growth rate of the açaí palm seedlings limits the crops' commercial expansion. The goal was evaluating the biometry, biomass accumulation, nutrient contents, chlorophyll-a fluorescence, and gas exchange in açaí seedlings inoculated with rhizobacteria. The treatments were individual inoculations of the seven rhizobacteria isolates and one control (without inoculation) on the roots. Biometry and biomass data were submitted to cluster analysis to separate the isolates into groups according to the similarity degree, and groups' means were compared through the SNK test. Three groups were formed; group 1 was composed of the control; group 2 of the UFRA-35, UFRA-38, UFRA-58, UFRA-61, UFRA-92, and BRM-32111 isolates; and group 3 was composed of the BRM-32113 isolate. Group 2 and 3 isolates promoted an increase in growth, biomass accumulation, higher levels of nutrients and chlorophyll, and improvements in the gas exchange and chlorophyll-a fluorescence in comparison with the control. The results evidenced that the rhizobacteria accelerate the growth, increase the photosynthetic efficiency, and induce the leaf nutrient accumulation in açaí palm seedlings. The rhizobacteria inoculation can contribute to the sustainable management of the açaí palm seedling production in nurseries.

A bioactivatable self-quenched nanogel for targeted photodynamic therapy

Photodynamic therapy has attracted significant attention due to its localized treatment advantage. However, the non-specific distribution of photosensitizers and the subsequent potential toxicity caused by sunshine exposure hinder its wide adoption in cancer treatment. To minimize these unwanted effects and improve its efficacy, we developed a bioactivatable self-quenched nanogel, which remains in its inactive state in healthy tissues. Anti-EGFR Affibody decorated nanogels can effectively target head and neck cancer and release activated pheophorbide A in a reducing environment, such as in the tumor stroma and cytoplasm. Consequently, the EGFR targeted nanogel coupled with NIR irradiation alleviates tumor burden by 94.5% while not inducing systemic toxicity.

Far-red light acclimation in diverse oxygenic photosynthetic organisms

Oxygenic photosynthesis has historically been considered limited to be driven by the wavelengths of visible light. However, in the last few decades, various adaptations have been discovered that allow algae, cyanobacteria, and even plants to utilize longer wavelength light in the far-red spectral range. These adaptations provide distinct advantages to the species possessing them, allowing the effective utilization of shade light under highly filtered light environments. In prokaryotes, these adaptations include the production of far-red-absorbing chlorophylls d and f and the remodeling of phycobilisome antennas and reaction centers. Eukaryotes express specialized light-harvesting pigment-protein complexes that use interactions between pigments and their protein environment to spectrally tune the absorption of chlorophyll a. If these adaptations could be applied to crop plants, a potentially significant increase in photon utilization in lower shaded leaves could be realized, improving crop yields.