Preparation and Properties of a Novel Biodegradable Composite Hydrogel Derived from Gelatin/Chitosan and Polylactic Acid as Slow-Release N Fertilizer.

To improve the efficient use of nitrogen and decrease the environmental pollution of N losses, a novel and biodegradable composite hydrogel was prepared by chemical cross-linking synthesis using gelatin (Gel), chitosan (CS) and polylactic acid (PLA) as raw materials. Urea as the nitrogen source was loaded into this new biodegradable hydrogel using the solution immersion method. The chemical structures of the composite hydrogels were characterized and their properties were analyzed by XRD and XPS. The regulation of urea loading and the swelling behavior of the composite hydrogel under different temperature conditions were investigated; the release behavior and release model of the composite hydrogel in the aqueous phase was explored. The results show that the loading of urea is controllable in aqueous urea solution with different concentrations. In the water phase, it shows a three-stage sustained release behavior, that is, the initial release rate of urea is relatively fast, and the medium release rate of urea gradually slows down, and finally the nutrient release rate tends to be flat. The release behavior in the water phase fits to the Ritger-Peppas model. Within 10 min, 180 min and 900 min, the cumulative nutrient release rate of gelatin/chitosan/PLA-urea (GCPU) composite hydrogel is 20%, 70% and 86%, respectively. Compared with pure urea, The urea diffusion time of GCPU was extended by 1350-times. In addition, the GCPU also has good water absorption and water retention properties, in which average water content can reach as high as 4448%. All of the results in this work showed that GCPU hydrogel had good water absorption and retention and N slow-release properties, which are expected to be widely used in sustainable agriculture and forestry, especially in arid and degraded land.

Preparation of PVA-CS/SA-Ca2+ Hydrogel with Core-Shell Structure.

Hydrogels are highly hydrophilic polymers that have been used in a wide range of applications. In this study, we prepared PVA-CS/SA-Ca2+ core-shell hydrogels with bilayer space by cross-linking PVA and CS to form a core structure and chelating SA and Ca2+ to form a shell structure to achieve multiple substance loading and multifunctional expression. The morphology and structure of core-shell hydrogels were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The factors affecting the swelling properties of the hydrogel were studied. The results show that the PVA-CS/SA-Ca2+ hydrogel has obvious core and shell structures. The SA concentration and SA/Ca2+ cross-linking time show a positive correlation with the thickness of the shell structure; the PVA/CS mass ratio affects the structural characteristics of the core structure; and a higher CS content indicates the more obvious three-dimensional network structure of the hydrogel. The optimal experimental conditions for the swelling degree of the core-shell hydrogel were an SA concentration of 5%; an SA/Ca2+ cross-linking time of 90 min; a PVA/CS mass ratio of 1:0.7; and a maximum swelling degree of 50 g/g.

Genome-Wide Identification and Function of Aquaporin Genes During Dormancy and Sprouting Periods of Kernel-Using Apricot (Prunus armeniaca L.).

Aquaporins (AQPs) are essential channel proteins that play a major role in plant growth and development, regulate plant water homeostasis, and transport uncharged solutes across biological membranes. In this study, 33 AQP genes were systematically identified from the kernel-using apricot (Prunus armeniaca L.) genome and divided into five subfamilies based on phylogenetic analyses. A total of 14 collinear blocks containing AQP genes between P. armeniaca and Arabidopsis thaliana were identified by synteny analysis, and 30 collinear blocks were identified between P. armeniaca and P. persica. Gene structure and conserved functional motif analyses indicated that the PaAQPs exhibit a conserved exon-intron pattern and that conserved motifs are present within members of each subfamily. Physiological mechanism prediction based on the aromatic/arginine selectivity filter, Froger's positions, and three-dimensional (3D) protein model construction revealed marked differences in substrate specificity between the members of the five subfamilies of PaAQPs. Promoter analysis of the PaAQP genes for conserved regulatory elements suggested a greater abundance of cis-elements involved in light, hormone, and stress responses, which may reflect the differences in expression patterns of PaAQPs and their various functions associated with plant development and abiotic stress responses. Gene expression patterns of PaAQPs showed that PaPIP1-3, PaPIP2-1, and PaTIP1-1 were highly expressed in flower buds during the dormancy and sprouting stages of P. armeniaca. A PaAQP coexpression network showed that PaAQPs were coexpressed with 14 cold resistance genes and with 16 cold stress-associated genes. The expression pattern of 70% of the PaAQPs coexpressed with cold stress resistance genes was consistent with the four periods [Physiological dormancy (PD), ecological dormancy (ED), sprouting period (SP), and germination stage (GS)] of flower buds of P. armeniaca. Detection of the transient expression of GFP-tagged PaPIP1-1, PaPIP2-3, PaSIP1-3, PaXIP1-2, PaNIP6-1, and PaTIP1-1 revealed that the fusion proteins localized to the plasma membrane. Predictions of an A. thaliana ortholog-based protein-protein interaction network indicated that PaAQP proteins had complex relationships with the cold tolerance pathway, PaNIP6-1 could interact with WRKY6, PaTIP1-1 could interact with TSPO, and PaPIP2-1 could interact with ATHATPLC1G. Interestingly, overexpression of PaPIP1-3 and PaTIP1-1 increased the cold tolerance of and protein accumulation in yeast. Compared with wild-type plants, PaPIP1-3- and PaTIP1-1-overexpressing (OE) Arabidopsis plants exhibited greater tolerance to cold stress, as evidenced by better growth and greater antioxidative enzyme activities. Overall, our study provides insights into the interaction networks, expression patterns, and functional analysis of PaAQP genes in P. armeniaca L. and contributes to the further functional characterization of PaAQPs.

The Osmotin-Like Protein Gene PdOLP1 Is Involved in Secondary Cell Wall Biosynthesis during Wood Formation in Poplar.

Osmotin-like proteins (OLPs) mediate defenses against abiotic and biotic stresses and fungal pathogens in plants. However, no OLPs have been functionally elucidated in poplar. Here, we report an osmotin-like protein designated PdOLP1 from Populus deltoides (Marsh.). Expression analysis showed that PdOLP1 transcripts were mainly present in immature xylem and immature phloem during vascular tissue development in P. deltoides. We conducted phenotypic, anatomical, and molecular analyses of PdOLP1-overexpressing lines and the PdOLP1-downregulated hybrid poplar 84K (Populus alba × Populus glandulosa) (Hybrid poplar 84K PagOLP1, PagOLP2, PagOLP3 and PagOLP4 are highly homologous to PdOLP1, and are downregulated in PdOLP1-downregulated hybrid poplar 84K). The overexpression of PdOLP1 led to a reduction in the radial width and cell layer number in the xylem and phloem zones, in expression of genes involved in lignin biosynthesis, and in the fibers and vessels of xylem cell walls in the overexpressing lines. Additionally, the xylem vessels and fibers of PdOLP1-downregulated poplar exhibited increased secondary cell wall thickness. Elevated expression of secondary wall biosynthetic genes was accompanied by increases in lignin content, dry weight biomass, and carbon storage in PdOLP1-downregulated lines. A PdOLP1 coexpression network was constructed and showed that PdOLP1 was coexpressed with a large number of genes involved in secondary cell wall biosynthesis and wood development in poplar. Moreover, based on transcriptional activation assays, PtobZIP5 and PtobHLH7 activated the PdOLP1 promoter, whereas PtoBLH8 and PtoWRKY40 repressed it. A yeast one-hybrid (Y1H) assay confirmed interaction of PtoBLH8, PtoMYB3, and PtoWRKY40 with the PdOLP1 promoter in vivo. Together, our results suggest that PdOLP1 is a negative regulator of secondary wall biosynthesis and may be valuable for manipulating secondary cell wall deposition to improve carbon fixation efficiency in tree species.

Proline-rich protein gene PdPRP regulates secondary wall formation in poplar.

Proline-rich protein (PRP) is a plant cell wall associated protein. Its distinct patterns of regulation and localization studied in a number of plants indicate that it may play important roles in growth and development. However, the mechanism of how these genes control secondary cell wall development in tree species is largely unknown. Here, we report that a Populus deltoides (Marsh.) proline-rich protein gene PdPRP was preferentially expressed in immature/mature phloem and immature xylem in P. deltoides. PdPRP overexpression increased poplar plant height and diameter as well as the radial width of the phloem and xylem regions, facilitated secondary wall deposition, and induced expression of genes related to microfibril angle (MFA) and secondary wall biosynthesis. Downregulation of PdPRP retarded poplar growth, decreased the radial width of the secondary phloem and secondary xylem regions, reduced secondary wall thickening in fibers and vessels, and decreased the expression of genes related to MFA and secondary wall biosynthesis. These results suggest that PdPRP might positively regulate secondary cell wall formation by promoting secondary wall thickening and expansion in poplar. PdPRP-overexpressing poplar had a lower MFA, indicating that PdPRP may be useful for improving wood stiffness and properties in plants. Together, our results demonstrate that PdPRP is a proline-rich protein associated with cell wall development, playing a critical role in regulating secondary cell wall formation in poplar.

[Study on hemolytic mechanism of polyphyllin II].

To study the hemolytic effect of polyphyllin II (PP II) mediated by anion channel protein and glucose transporter 1 (GLUT1), in order to initially reveal its hemolytic mechanism in vitro. In the experiment, the spectrophotometric method was adopted to detect the hemolysis of PP II in vitro and the effect of anion channel-related solution and blocker, glucose channel-related inhibitor and multi-target drugs dehydroepiandrosterone (DHEA) and diazepam on the hemolysis of PP II. The scanning electron microscope and transmission electron microscope were used to observe the effect of PP II on erythrocyte (RBC) morphology. The results showed that PP II -processed blood cells were severely deformed into spherocytes, acanthocyturia and vesicae. According to the results of the PP II hemolysis experiment in vitro, the anion hypertonic solution LiCl, NaHCO3, Na2SO4 and PBS significantly inhibited the hemolysis induced by PP II (P < 0.05), while blockers NPPB and DIDS remarkably promoted it (P < 0.01). Hyperosmotic sodium chloride, fructose and glucose at specific concentrations notably antagonized the hemolysis induced by PP II (P < 0.05). The glucose channel inhibitor Cytochalasin B and verapamil remarkably antagonized the hemolysis induced by PP II (P < 0.01). The hemolysis induced by PP II could also be antagonized by 1 gmol x L(1) diazepam and 100 µmol x L(-1) DHEA pretreated for 1 min (P < 0.01). In conclusion, the hemolytic mechanism of PP II in vitro may be related to the increase in intracellular osmotic pressure and rupture of erythrocytes by changing the anion channel transport activity, with GLUT1 as the major competitive interaction site.