H3K79 methylation promotes rapid growth of Alexandrium pacificum under high light intensity via increased photosynthesis.

Alexandrium pacificum is one of the main species responsible for harmful algal blooms, posing serious threats to coastal ecosystems, economies, and public health. Light intensity is an important abiotic factor affecting the occurrence of red tides. In a certain range, increasing light intensity can promote the rapid growth of A. pacificum. This study aimed to elucidate the molecular mechanisms of H3K79 methylation (H3K79me) in response to high light intensity during the rapid growth of A. pacificum and the formation of toxic red tides. The research found that the abundance of H3K79me increased 2.1-fold under high light (HL, 60 µmol photon m-2 s-l) compared to control light conditions (CT, 30 µmol photon m-2 s-l), which was consistent with the trend of rapid growth under HL, and both can be inhibited by EPZ5676. Then effector genes of H3K79me under HL were identified using ChIP-seq and a virtual genome constructed based on transcriptome data of A. pacificum for the first time. The results showed that the differential modification-associated genes were primarily enriched in the pathways of "energy metabolism", "carbon metabolism", and "amino acid metabolism". These findings were confirmed through ChIP-qPCR. Subsequently, H3K79me-associated genes CP43 and GOGAT were identified by combined analysis of ChIP-seq and differentially expressed genes. Finally, pharmacological experiments using the H3K79me inhibitor EPZ5676 showed that the expression of the photosynthesis-related gene CP43 was significantly reduced by 2.5-fold and the maximum photochemical quantum efficiency of A. pacificum was reduced by 1.2 to 1.8-fold in HL compared with CT, leading to inhibited growth of A. pacificum. These results suggest that H3K79me plays a role in regulating the rapid growth of A. pacificum and photosynthesis is likely an important regulatory pathway, which is the first to provide epigenetic evidence underlying the formation of toxic red tides from the perspective of H3K79me.

The H3K79 methylase DOT1, unreported in photosynthetic plants, exists in Alexandrium pacificum and participates in its growth regulation.

Alexandrium pacificum is one of the typical toxic dinoflagellate species leading to harmful algal blooms (HABs). Histone modifications play key roles in many cellular events, but little is known about the mechanism of regulating A. pacificum growth. In this study, a total of 30 proteins containing the DOT1 domain were identified and analyzed. Some ApDOT1 gene expression levels were significantly influenced by light intensity and nitrogen by expression analysis and RT-qPCR validation. The enrichment of H3K79 methylation also showed a similar trend. In addition, ApDOT1.9 protein was proved to have the function of catalyzing the methylation of H3K79 by homology analysis and in vitro methylation. The results suggested that ApDOT1 proteins and H3K79 methylation were involved in responding to harmful algal blooms-inducing conditions (high light intensity, and high nitrogen), which provided basic information for further exploration of the regulatory mechanism of histone methylation in A. pacificum rapid growth.

Identification of epigenetic histone modifications and analysis of histone lysine methyltransferases in Alexandrium pacificum.

Alexandrium pacificum is a toxic dinoflagellate that can cause harmful algal blooms (HABs). The molecular mechanisms of HABs are still poorly understood, especially at the epigenetics level. Organism growth and metabolic processes are affected by histone modifications, an important mode of epigenetic regulation. In this study, various types of modifications, including methylation, acetylation, ubiquitination, and phosphorylation in A. pacificum cells were identified by using pan-antibodies, mass spectrometry, and an H3 modification multiplex assay kit. The modification abundance of H3K4me2 and H3K27me3 of A. pacificum varied under different growth conditions detected by Western blots. A class of SET domain genes (SDGs) encoding histone lysine methyltransferase was analyzed. A total of 179 SDG members were identified in A. pacificum, of which 53 sequences encoding complete proteins were classified into three categories by phylogenetic analysis, conserved domains and motifs analysis. Expression analysis and real-time polymerase chain reaction validation showed that the expressions of some SDGs were significantly influenced by light, nitrogen, phosphorus and manganese supplements. The results revealed that histone lysine methylation played an important role in responding to HABs inducing conditions. This study provided useful information for the further exploration of the role and regulatory mechanism of SDGs in the rapid growth of A. pacificum.

Ectomycorrhizal Fungal Strains Facilitate Cd2+ Enrichment in a Woody Hyperaccumulator under Co-Existing Stress of Cadmium and Salt.

Cadmium (Cd2+) pollution occurring in salt-affected soils has become an increasing environmental concern in the world. Fast-growing poplars have been widely utilized for phytoremediation of soil contaminating heavy metals (HMs). However, the woody Cd2+-hyperaccumulator, Populus × canescens, is relatively salt-sensitive and therefore cannot be directly used to remediate HMs from salt-affected soils. The aim of the present study was to testify whether colonization of P. × canescens with ectomycorrhizal (EM) fungi, a strategy known to enhance salt tolerance, provides an opportunity for affordable remediation of Cd2+-polluted saline soils. Ectomycorrhization with Paxillus involutus strains facilitated Cd2+ enrichment in P. × canescens upon CdCl2 exposures (50 µM, 30 min to 24 h). The fungus-stimulated Cd2+ in roots was significantly restricted by inhibitors of plasmalemma H+-ATPases and Ca2+-permeable channels (CaPCs), but stimulated by an activator of plasmalemma H+-ATPases. NaCl (100 mM) lowered the transient and steady-state Cd2+ influx in roots and fungal mycelia. Noteworthy, P. involutus colonization partly reverted the salt suppression of Cd2+ uptake in poplar roots. EM fungus colonization upregulated transcription of plasmalemma H+-ATPases (PcHA4, 8, 11) and annexins (PcANN1, 2, 4), which might mediate Cd2+ conductance through CaPCs. EM roots retained relatively highly expressed PcHAs and PcANNs, thus facilitating Cd2+ enrichment under co-occurring stress of cadmium and salinity. We conclude that ectomycorrhization of woody hyperaccumulator species such as poplar could improve phytoremediation of Cd2+ in salt-affected areas.

Polycysteine as a new type of radio-protector ameliorated tissue injury through inhibiting ferroptosis in mice.

Amifostine has been the only small molecule radio-protector approved by FDA for decades; however, the serious adverse effects limit its clinical use. To address the toxicity issues and maintain the good potency, a series of modified small polycysteine peptides had been prepared. Among them, compound 5 exhibited the highest radio-protective efficacy, the same as amifostine, but much better safety profile. To confirm the correlation between the radiation-protective efficacy and the DNA binding capability, each of the enantiomers of the polycysteine peptides had been prepared. As a result, the L-configuration compounds had obviously higher efficacy than the corresponding D-configuration enantiomers; among them, compound 5 showed the highest DNA binding capability and radiation-protective efficacy. To our knowledge, this is the first study that has proved their correlations using direct comparison. Further exploration of the mechanism revealed that the ionizing radiation (IR) triggered ferroptosis inhibition by compound 5 could be one of the pathways for the protection effect, which was different from amifostine. In summary, the preliminary result showed that compound 5, a polycysteine as a new type of radio-protector, had been developed with good efficacy and safety profile. Further study of the compound for potential use is ongoing.

Calmodulin and Its Interactive Proteins Participate in Regulating the Explosive Growth of Alexandrium pacificum (Dinoflagellate).

Alexandrium pacificum is a typical dinoflagellate that can cause harmful algal blooms, resulting in negative impacts on ecology and human health. The calcium (Ca2+) signal transduction pathway plays an important role in cell proliferation. Calmodulin (CaM) and CaM-related proteins are the main cellular Ca2+ sensors, and can act as an intermediate in the Ca2+ signal transduction pathway. In this study, the proteins that interacted with CaM of A. pacificum were screened by two-dimensional electrophoresis analysis and far western blots under different growth conditions including lag phase and high phosphorus and manganese induced log phase (HPM). The interactive proteins were then identified using matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Four proteins were identified, including Ca2+/CaM-dependent protein kinase, serine/threonine kinase, annexin, and inositol-3-phosphate synthase, which all showed high expression levels under HPM. The gene expression levels encoding these four proteins were also up-regulated under HPM, as revealed by quantitative polymerase chain reaction, suggesting that the identified proteins participate in the Ca2+ transport channel and cell cycle regulation to promote cell division. A network of proteins interacting with CaM and their target proteins involved in the regulation of cell proliferation was raised, which provided new insights into the mechanisms behind the explosive growth of A. pacificum.

[Effects of activated water irrigation on growth characteristics of soybean under drought stress]. / 干旱胁迫下活化水灌溉对大豆生长特征的影响.

To understand the effects of activated water irrigation on soybean growth under different drought conditions and explore the underlying mechanisms, an indoor pot experiment was conducted under four moisture conditions of 95%-100%, 75%-85%, 55%-65% and 35%-45% of the maximum water holding capacity (80% moisture) of the medium. Soybean was irrigated with tap water, magnetized water, aerated water, and magnetized and then aerated water, respectively. The results showed that total biomass, leaf area, root to shoot ratio, and root length of magnetized water irrigation increased by 67.6%, 23.5%, 84.6% and 122.8%, respectively compared with tap water irrigation after 30 days of growth under 35%-45% severe drought condition. All the variables were increased by 70.8%, 24.0%, 61.9% and 162.3% respectively in magnetized and aerated water treatment. There was no significant difference for foliar chlorophyll content. The values of the other water treatments were slightly lower than that of tap water. In conclusion, magnetized water irrigation effectively enhanced root growth, root-shoot ratio, and water use efficiency of soybean, and alleviated the negative effects of drought stress under severe drought condition.

Amelioration of nitrate uptake under salt stress by ectomycorrhiza with and without a Hartig net.

Salt stress is an important environmental cue impeding poplar nitrogen nutrition. Here, we characterized the impact of salinity on proton-driven nitrate fluxes in ectomycorrhizal roots and the importance of a Hartig net for nitrate uptake. We employed two Paxillus involutus strains for root colonization: MAJ, which forms typical ectomycorrhizal structures (mantle and Hartig net), and NAU, colonizing roots with a thin, loose hyphal sheath. Fungus-colonized and noncolonized Populus × canescens were exposed to sodium chloride and used to measure root surface pH, nitrate (NO3- ) flux and transcription of NO3- transporters (NRTs; PcNRT1.1, -1.2, -2.1), and plasmalemma proton ATPases (HAs; PcHA4, -8, -11). Paxillus colonization enhanced root NO3- uptake, decreased surface pH, and stimulated NRTs and HA4 of the host regardless the presence or absence of a Hartig net. Under salt stress, noncolonized roots exhibited strong net NO3- efflux, whereas beneficial effects of fungal colonization on surface pH and HAs prevented NO3- loss. Inhibition of HAs abolished NO3- influx under all conditions. We found that stimulation of HAs was crucial for the beneficial influence of ectomycorrhiza on NO3- uptake, whereas the presence of a Hartig net was not required for improved NO3- translocation. Mycorrhizas may contribute to host adaptation to salt-affected environments by keeping up NO3- nutrition.

Pinocembrin Protects Blood-Brain Barrier Function and Expands the Therapeutic Time Window for Tissue-Type Plasminogen Activator Treatment in a Rat Thromboembolic Stroke Model.

Tissue-type plasminogen activator (t-PA) remains the only approved therapy for acute ischemic stroke but has a restrictive treatment time window of 4.5 hr. Prolonged ischemia causes blood-brain barrier (BBB) damage and increases the incidence of hemorrhagic transformation (HT) secondary to reperfusion. In this study, we sought to determine the effect of pinocembrin (PCB; a pleiotropic neuroprotective agent) on t-PA administration-induced BBB damage in a novel rat thromboembolic stroke model. By assessing the leakage of Evans blue into the ischemic hemisphere, we demonstrated that PCB pretreatment 5 min before t-PA administration significantly reduced BBB damage following 2 hr, 4 hr, 6 hr, and even 8 hr ischemia. Consistently, PCB pretreatment significantly decreased t-PA infusion-resulting brain edema and infarction volume and improved the behavioral outcomes following 6 hr ischemia. Mechanistically, PCB pretreatment inhibited the activation of MMP-2 and MMP-9 and degradation of tight junction proteins (TJPs) occludin and claudin-5 in the ischemic hemisphere. Moreover, PCB pretreatment significantly reduced phosphorylation of platelet-derived growth factor receptor α (PDGFRα) as compared with t-PA alone. In an in vitro BBB model, PCB decreased transendothelial permeability upon hypoxia/aglycemia through inhibiting PDGF-CC secretion. In conclusion, we demonstrated that PCB pretreatment shortly before t-PA infusion significantly protects BBB function and improves neurological outcomes following prolonged ischemia beyond the regular 4.5 hr t-PA time window. PCB pretreatment may represent a novel means of increasing the safety and the therapeutic time window of t-PA following ischemic stroke.

Paxillus involutus-Facilitated Cd2+ Influx through Plasma Membrane Ca2+-Permeable Channels Is Stimulated by H2O2 and H+-ATPase in Ectomycorrhizal Populus × canescens under Cadmium Stress.

Using a Non-invasive Micro-test Technique, flux profiles of Cd2+, Ca2+, and H+ were investigated in axenically grown cultures of two strains of Paxillus involutus (MAJ and NAU), ectomycorrhizae formed by these fungi with the woody Cd2+-hyperaccumulator, Populus × canescens, and non-mycorrhizal (NM) roots. The influx of Cd2+ increased in fungal mycelia, NM and ectomycorrhizal (EM) roots upon a 40-min shock, after short-term (ST, 24 h), or long-term (LT, 7 days) exposure to a hydroponic environment of 50 µM CdCl2. Cd2+ treatments (shock, ST, and LT) decreased Ca2+ influx in NM and EM roots but led to an enhanced influx of Ca2+ in axenically grown EM cultures of the two P. involutus isolates. The susceptibility of Cd2+ flux to typical Ca2+ channel blockers (LaCl3, GdCl3, verapamil, and TEA) in fungal mycelia and poplar roots indicated that the Cd2+ entry occurred mainly through Ca2+-permeable channels in the plasma membrane (PM). Cd2+ treatment resulted in H2O2 production. H2O2 exposure accelerated the entry of Cd2+ and Ca2+ in NM and EM roots. Cd2+ further stimulated H+ pumping activity benefiting NM and EM roots to maintain an acidic environment, which favored the entry of Cd2+ across the PM. A scavenger of reactive oxygen species, DMTU, and an inhibitor of PM H+-ATPase, orthovanadate, decreased Ca2+ and Cd2+ influx in NM and EM roots, suggesting that the entry of Cd2+ through Ca2+-permeable channels is stimulated by H2O2 and H+ pumps. Compared to NM roots, EM roots exhibited higher Cd2+-fluxes under shock, ST, and LT Cd2+ treatments. We conclude that ectomycorrhizal P. × canescens roots retained a pronounced H2O2 production and a high H+-pumping activity, which activated PM Ca2+ channels and thus facilitated a high influx of Cd2+ under Cd2+ stress.

[Changes of four common plant populations growth and their anti-oxidative enzymatic system in desertification process].

This paper studied the changes of the growth and anti-oxidative enzymatic system of four common plant populations during the desertification process of sandy grassland. The results showed that in the process of desertification, the individual height and density and the density percentage of the populations all had a decreasing trend. The growth of Melilotoides ruthenica was more vigorous before moderate desertification (MD) stage, but restricted after that. In MD stage, the growth of Leymus chinensis was heavily restricted, and its individual height, density and density percentage accounted for 57.19%, 2.50% and 6.22% of those in original vegetation (OV) stage, respectively. The individual height and density of Cleistogenes squarrosa and Artemisia frigida increased in the stages of potential desertification (PD), light desertification (LD) or MD because of their phase status of dominant species and their stronger stress resistance. The SOD and POD activities of the common plant populations increased in PD and MD stages, but decreased in LD and heavy desertification (HD) stages. The CAT activity of Leymus chinensis was higher, whose response to desertification was not significant (P > 0.05), and that of Melilotoides ruthenica increased significantly in PD and HD stages (P < or = 0.01). The activities of the three anti-oxidative enzymes in the common plant populations, except the CAT activity of Melilotoides ruthenica, decreased in HD stage. The MDA content in the common populations increased firstly, then decreased, and finally increased from OV to MD stage, and had a significant difference in different desertification gradients (P < or = 0.05). Based on the integrated analysis of the ecological and physiological changes, it could be concluded that Leymus chinensis was more sensitive to desertification, while Melilotoides ruthenica had a stronger bioenergy.

[Soil C and N dynamics during desertification of grassland in Northern China].

This paper investigated the aboveground vegetations and the soil texture and total C and N at 75 sites of Duolun County in Xilinguole League of Inner Mongolia. The results showed that different types of vegetation community could be used to describe different stages of desertification process. During desertification, the community types were changed in the series of Leymus chinensis + Cleistogenes squarrosa --> Artemisia frigida --> Artemisia intramongolia --> Corispermum staunyonii, Chenopodium bryoniaefolium --> drift sand, and a regular change of soil clay and total C and N contents could also be found. The soil C/N ratio was increased with different stages of grassland desertification, which could be expressed in the series of 8.11-->13.96-->12.36-->28.17.