Flexible and Compressible Nanostructure-Assembled Aramid Nanofiber/Silica Composites Aerogel.

The Applications of silica aerogel are limited due to its brittleness and low strength. As a result, it is essential to strengthen and toughen it. Organic nanofibers are one of the preferred reinforcement materials. In this work, we designed and fabricated flexible and compressible nanostructure-assembled aramid nanofiber/silica composites aerogel (ANF/SiO2 aerogel) to improve the mechanical strength and flexibility of silica aerogel without compromising thermal insulation properties. The aramid nanofiber/silica composite aerogels were prepared by immersing the aramid nanofiber wet gel into the silica sol for a certain period of time followed by freeze drying without solvent replacement. The surface modifier 3-aminopropyltriethoxysilane (APTES) was used as a coupling agent to form chemical linkage between the ANF fiber and silica gel. It was observed that APTES can effectively drive the silica sol to infuse into ANF hydrogel, promoting the assembly of silica gel onto the fiber surface and a uniform distribution in the network of ANF. The compressive resilience, thermal stability, and thermal insulation properties of the composite aerogels were evaluated by inducing the silica aerogel into the ANF network to form a protective layer on the fiber and change the pore structure in the ANF network.

Genomic insights into Aspergillus sydowii 29R-4-F02: unraveling adaptive mechanisms in subseafloor coal-bearing sediment environments.

Introduction: Aspergillussydowii is an important filamentous fungus that inhabits diverse environments. However, investigations on the biology and genetics of A. sydowii in subseafloor sediments remain limited. Methods: Here, we performed de novo sequencing and assembly of the A. sydowii 29R-4-F02 genome, an isolate obtained from approximately 2.4 km deep, 20-million-year-old coal-bearing sediments beneath the seafloor by employing the Nanopore sequencing platform. Results and Discussion: The generated genome was 37.19 Mb with GC content of 50.05%. The final assembly consisted of 11 contigs with N50 of 4.6 Mb, encoding 12,488 putative genes. Notably, the subseafloor strain 29R-4-F02 showed a higher number of carbohydrate-active enzymes (CAZymes) and distinct genes related to vesicular fusion and autophagy compared to the terrestrial strain CBS593.65. Furthermore, 257 positively selected genes, including those involved in DNA repair and CAZymes were identified in subseafloor strain 29R-4-F02. These findings suggest that A. sydowii possesses a unique genetic repertoire enabling its survival in the extreme subseafloor environments over tens of millions of years.

The potential role of subseafloor fungi in driving the biogeochemical cycle of nitrogen under anaerobic conditions.

Fungi represent the dominant eukaryotic group of organisms in anoxic marine sedimentary ecosystems, ranging from a few centimeters to ~ 2.5 km below seafloor. However, little is known about how fungi can colonize anaerobic subseafloor environments for tens of millions of years and whether they play a role in elemental biogeochemical cycles. Based on metabolite detection, isotope tracer and gene analysis, we examined the anaerobic nitrogen conversion pathways of 19 fungal species (40 strains) isolated from1.3 to 2.5 km coal-bearing sediments below seafloor. Our results show for the first time that almost all fungi possess anaerobic denitrification, dissimilatory nitrate reduction to ammonium (DNRA), and nitrification pathways, but not anaerobic ammonium oxidation (anammox). Moreover, the distribution of fungi with different nitrogen-conversion abilities in subseafloor sediments was mainly determined by in situ temperature, CaCO3, and inorganic carbon contents. These findings suggest that fungi have multiple nitrogen transformation processes to cope with their requirements for a variety of nitrogen sources in nutrient deficient anaerobic subseafloor sedimentary environments.

Anaerobic biodegradation of polycyclic aromatic hydrocarbons (PAHs) by fungi isolated from anaerobic coal-associated sediments at 2.5 km below the seafloor.

Fungi represent the dominant eukaryotic group in the deep biosphere and well-populated in the anaerobic coal-bearing sediments up to ∼2.5 km below seafloor (kmbsf). But whether fungi are able to degrade and utilize coal to sustain growth in the anaerobic sub-seafloor environment remains unknown. Based on biodegradation investigation, we found that fungi isolated from sub-seafloor sediments at depths of ∼1.3-∼2.5 kmbsf showed a broad range of polycyclic aromatic hydrocarbons (PAHs) anaerobic degradation rates (3-25%). Among them, the white-rot fungus Schizophyllium commune 20R-7-F01 exhibited the highest degradation, 25%, 18% and 13%, of phenanthrene (Phe), pyrene (Pyr) and benzo[a]pyrene (BaP); respectively, after 10 days of anaerobic incubation. Phe was utilized well and about 40.4% was degraded by the fungus, after 20 days of anaerobic incubation. Moreover, the ability of fungi to degrade PAHs was positively correlated with the anaerobic growth of fungi, indicating that fungi can use PAHs as a sole carbon source under anoxic conditions. In addition, fungal degradation of PAHs was found to be related to the activity of carboxylases, but little or nothing to do with the activity of lignin modifying enzymes such as laccase (Lac), manganese peroxidase (MnP) and lignin peroxidase (LiP). These results suggest that sub-seafloor fungi possess a special mechanism to degrade and utilize PAHs as a carbon and energy source under anaerobic conditions. Furthermore, fungi living in sub-seafloor sediments may not only play an important role in carbon cycle in the anaerobic environments of the deep biosphere, but also be able to persist in deep sediment below seafloor for millions of years by using PAHs or related compounds as carbon and energy source. This anaerobic biodegradation ability could make these fungi suitable candidates for bioremediation of toxic pollutants such as PAHs from anoxic environments.

TaAMT2;3a, a wheat AMT2-type ammonium transporter, facilitates the infection of stripe rust fungus on wheat.

BACKGROUND: Ammonium transporters (AMTs), a family of proteins transporting ammonium salt and its analogues, have been studied in many aspects. Although numerous studies have found that ammonium affects the interaction between plants and pathogens, the role of AMTs remains largely unknown, especially that of the AMT2-type AMTs. RESULTS: In the present study, we found that the concentration of ammonium in wheat leaves decreased after infection with Puccinia striiformis f. sp. tritici (Pst), the causal agent of stripe rust. Then, an AMT2-type ammonium transporter gene induced by Pst was identified and designated as TaAMT2;3a. Transient expression assays indicated that TaAMT2;3a was located to the cell and nuclear membranes. TaAMT2;3a successfully complemented the function of a yeast mutant defective in NH4+ transport, indicating its ammonium transport capacity. Function of TaAMT2;3a in wheat-Pst interaction was further analyzed by barley stripe mosaic virus (BSMV)-induced gene silencing. Pst growth was significantly retarded in TaAMT2;3a-knockdown plants, in which ammonium in leaves were shown to be induced at the early stage of infection. Histological observation showed that the hyphal length, the number of hyphal branches and haustorial mother cells decreased in the TaAMT2;3a knockdown plants, leading to the impeded growth of rust pathogens. CONCLUSIONS: The results clearly indicate that the induction of AMT2-type ammonium transporter gene TaAMT2;3a may facilitates the nitrogen uptake from wheat leaves by Pst, thereby contribute to the infection of rust fungi.

The heat-tolerance evaluation of an Isochrysis zhangjiangensis mutant generated by atmospheric and room temperature plasmas.

Isochrysis zhangjiangensis is widely used in the marine aquaculture as larval feed, especially for filter feeding cultures, as well as a good candidate for biofuels. However, the optimal cultivation temperature for I. zhangjiangensis is below 30 °C and this stain is seriously affected by high temperature, which causes the limited application during the summer. I. zhangjiangensis IM130005 is a strain generated by atmospheric and room temperature plasmas with relative higher growth rate and lipid production than the wide strain (WT), with the ability to tolerate several hours' high temperature during the outdoor cultivation. Here, a detailed comparison was performed by continuous monitoring growth, chlorophyll fluorescence and fatty acid profile between IM13005 and WT under a mimic temperature shock to the summer outdoor cultivation. Based on a nearly 20% increase of total fatty acid in IM13005, which was majorly contributed by saturated or monounsaturated FAs in form of neutral lipids, within 5 h under the heat shock, the fatty acids and lipids synthesis variation were postulated as the physiological reason for the high temperature tolerance.

Phosphorus Enhances Photosynthetic Storage Starch Production in a Green Microalga (Chlorophyta) Tetraselmis subcordiformis in Nitrogen Starvation Conditions.

Microalgae are potential starch producers as alternatives to agricultural crops. This study disclosed the effects and mechanism of phosphorus availability exerted on storage starch production in a starch-producing microalga Tetraselmis subcordiformis in nitrogen starvation conditions. Excessive phosphorus supply facilitated starch production, which differed from the conventional cognition that phosphorus would inhibit transitory starch biosynthesis in plants. Phosphorus enhanced energy utilization efficiency for biomass and storage starch production. ADP-glucose pyrophosphorylase (AGPase), conventionally known to be critical for starch biosynthesis, was negatively correlated to storage starch biosynthesis. Excessive phosphorus supply maintained large cell volumes, enhanced activities of starch phosphorylases (SPs) along with branching enzymes and isoamylases, and increased phosphoenolpyruvate and trehalose-6-phosphate levels to alleviate the inhibition of high phosphate availability to AGPase, all of which improved starch production. This work highlighted the importance of phosphorus in the production of microalgal starch and provided further evidence for the SP-based storage starch biosynthesis pathway.

Genetic Architecture of Natural Variation in Rice Nonphotochemical Quenching Capacity Revealed by Genome-Wide Association Study.

The photoprotective processes conferred by nonphotochemical quenching (NPQ) serve fundamental roles in maintaining plant fitness and sustainable yield. So far, few loci have been reported to be involved in natural variation of NPQ capacity in rice (Oryza sativa), and the extents of variation explored are very limited. Here we conducted a genome-wide association study (GWAS) for NPQ capacity using a diverse worldwide collection of 529 O. sativa accessions. A total of 33 significant association loci were identified. To check the validity of the GWAS signals, three F2 mapping populations with parents selected from the association panel were constructed and assayed. All QTLs detected in mapping populations could correspond to at least one GWAS signal, indicating the GWAS results were quite reliable. OsPsbS1 was repeatedly detected and explained more than 40% of the variation in the whole association population in two years, and demonstrated to be a common major QTL in all three mapping populations derived from inter-group crosses. We revealed 43 single nucleotide polymorphisms (SNPs) and 7 insertions and deletions (InDels) within a 6,997-bp DNA fragment of OsPsbS1, but found no non-synonymous SNPs or InDels in the coding region, indicating the PsbS1 protein sequence is highly conserved. Haplotypes with the 2,674-bp insertion in the promoter region exhibited significantly higher NPQ values and higher expression levels of OsPsbS1. The OsPsbS1 RNAi plants and CRISPR/Cas9 mutants exhibited drastically decreased NPQ values. OsPsbS1 had specific and high-level expression in green tissues of rice. However, we didn't find significant function for OsPsbS2, the other rice PsbS homologue. Manipulation of the significant loci or candidate genes identified may enhance photoprotection and improve photosynthesis and yield in rice.

Chloroplasts Isolation from Chlamydomonas reinhardtii under Nitrogen Stress.

Triacylglycerols are produced in abundance through chloroplast and endoplasmic reticulum pathways in some microalgae exposed to stress, though the relative contribution of either pathway remains elusive. Characterization of these pathways requires isolation of the organelles. In this study, an efficient and reproducible approach, including homogenous batch cultures of nitrogen-deprived algal cells in photobioreactors, gentle cell disruption using a simple custom-made disruptor with mechanical shear force, optimized differential centrifugation and Percoll density gradient centrifugation, was developed to isolate chloroplasts from Chlamydomonas reinhardtii subjected to nitrogen stress. Using this approach, the maximum limited stress duration was 4 h and the stressed cells exhibited 19 and 32% decreases in intracellular chlorophyll and nitrogen content, respectively. Chloroplasts with 48 - 300 µg chlorophyll were successfully isolated from stressed cells containing 10 mg chlorophyll. These stressed chloroplasts appeared intact, as monitored by ultrastructure observation and a novel quality control method involving the fatty acid biomarkers. This approach can provide sufficient quantities of intact stressed chloroplasts for subcellular biochemical studies in microalgae.

Characterization of starch phosphorylase from the marine green microalga (Chlorophyta) Tetraselmis subcordiformis reveals its potential role in starch biosynthesis.

In a marine green starch-producing microalga Tetraselmis subcordiformis, the role of starch phosphorylase (SP) in the starch biosynthesis was disclosed by characterizing the enzyme properties and activity variations during the starch accumulation process. TsSP4, a SP isoform accounting for the major SP activity in T. subcordiformis, was unique to be active in a monomer form with a molecular weight of approximately 110kDa. It resembled one of the chloroplast-located SPs (PhoA) in Chlamydomonas reinhardtii with a similarity of 63.3% in sequence, though it possessed the typical L78/80 domain found in the plastidial SPs (Pho1) of higher plants that was absent in PhoA. TsSP4 exhibited moderate sensitivity to ADP-Glc inhibition and had a high activity for longer-chain linear maltooligosacchride (MOS) and amylopectin against highly branched glycogen as the substrates. TsSP4 had 2-fold higher affinity for Glc-1-P in the synthetic direction than for Pi in the phosphorolytic direction, and the catalytic constant kcat for Glc-1-P was 2-fold of that for Pi. Collectively, TsSP4 preferred synthetic rather than phosphorolytic direction. TsSP4 could elongate MOSs even initially with Pi alone in the absence of Glc-1-P, which further supported its synthetic role in the starch biosynthesis. TsSP4 displayed increased activities in the developing and mature stage of starch biosynthesis under nitrogen-starvation conditions, indicating its possible contribution to the amylopectin amplification.

AvrXa27 binding influences unwinding of the double-stranded DNA in the UPT box.

Transcription-Activator Like (TAL) effectors, delivered by Xanthomonas pathogens bind specifically to UP-regulated by TAL effectors (UPT) box of the host gene promoter to arouse disease or trigger defense response. This type of protein-DNA interaction model has been applied in site-directed genome editing. However, the off-target effects of TAL have severely hindered the development of this promising technology. To better exploit the specific interaction and to deeper understand the TAL-induced host transcription rewiring, the binding between the central repeat region (CRR) of the TAL effector AvrXa27 and its UPT box variants was studied by kinetics analysis and TAL-blocked helicase unwinding assay. The results revealed that while AvrXa27 exhibited the highest affinity to the wild type UPT box, it could also bind to mutated UPT box variants, implying the possibility of non-specific interactions. Furthermore, some of these non-specific combinations restricted the helicase-elicited double-stranded DNA (dsDNA) separation to a greater extent. Our findings provide insight into the mechanism of TAL transcriptional activation and are beneficial to TAL-mediated genome modification.

The characteristics of TAG and EPA accumulation in Nannochloropsis oceanica IMET1 under different nitrogen supply regimes.

The strategy of nitrogen limitation has been widely applied to enhance lipid production in microalgae. The changes of cellular composition, and the characteristics of triacylglycerol (TAG) and eicosapentaenoic acid (EPA) accumulation in Nannochloropsis oceanica IMET1 were investigated. The results revealed that after nitrogen limitation TAG rather than carbohydrate was the dominant carbon sink in N. oceanica IMET1. Different nitrogen supplementation strategies were applied in order to achieve high TAG and EPA productivity, respectively. Limited nitrogen was supplied to improve TAG production, and a maximum productivity of 29.44 mg L(-1) d(-1) was obtained, which was a 6.74-fold increase compared to nitrogen-depleted cultivation. The highest EPA productivity of 7.66 mg L(-1) d(-1) was achieved under nitrogen-replete cultivation, which is different from the condition for TAG maximum productivity because the EPA is in glycolipids and phospholipids mainly. The fatty acid composition analysis identified the source of acyl group in TAG accumulation.