Effects of Multi-Walled Carbon Nanotubes and Nano-Silica on Root Development, Leaf Photosynthesis, Active Oxygen and Nitrogen Metabolism in Maize.

Carbon nanotubes (MWCNTs) and nano-silica (nano-SiO2) are widely used in the field of life science because of their special physical and chemical properties. In this study, the effects of different concentrations of MWCNTs (0 mg·L-1, 200 mg·L-1, 400 mg·L-1, 800 mg·L-1 and 1200 mg·L-1) and nano-SiO2 (0 mg·L-1, 150 mg·L-1, 800 mg·L-1, 1500 mg·L-1 and 2500 mg·L-1) on maize seedling growth and relative mechanisms were explored. The main results are as follows: MWCNTs and nano-SiO2 can promote the growth of maize seedlings, and promote plant height, root length, the dry and fresh weight of seedlings, root-shoot ratio and so on. The ability to accumulate dry matter increased, the relative water content of leaves increased, the electrical conductivity of leaves decreased, the stability of cell membranes improved and the water metabolism ability of maize seedlings increased. The treatment of MWCNTs with 800 mg·L-1 and nano-SiO2 with 1500 mg·L-1 had the best effect on seedling growth. MWCNTs and nano-SiO2 can promote the development of root morphology, increase root length, root surface area, average diameter, root volume and total root tip number and improve root activity, so as to improve the absorption capacity of roots to water and nutrition. After MWCNT and nano-SiO2 treatment, compared with the control, the contents of O2·- and H2O2 decreased, and the damage of reactive oxygen free radicals to cells decreased. MWCNTs and nano-SiO2 can promote the clearance of reactive oxygen species and maintain the complete structure of cells, so as to slow down plant aging. The promoting effect of MWCNTs treated with 800 mg·L-1 and nano-SiO2 treated with 1500 mg·L-1 had the best effect. After treatment with MWCNTs and nano-SiO2, the activities of key photosynthesis enzymes PEPC, Rubisco, NADP-ME, NADP-MDH and PPDK of maize seedlings increased, which promoted the opening of stomata, improved the fixation efficiency of CO2, improved the photosynthetic process of maize plants and promoted plant growth. The promoting effect was the best when the concentration of MWCNTs was 800 mg·L-1 and the concentration of nano-SiO2 was 1500 mg·L-1. MWCNTs and nano-SiO2 can increase the activities of the enzymes GS, GOGAT, GAD and GDH related to nitrogen metabolism in maize leaves and roots, and can increase the content of pyruvate, so as to promote the synthesis of carbohydrates and the utilization of nitrogen and promote plant growth.

Characterizing corn-straw-degrading actinomycetes and evaluating application efficiency in straw-returning experiments.

Corn straw is an abundant lignocellulose resource and by-product of agricultural production. With the continuous increase in agricultural development, the output of corn straw is also increasing significantly. However, the inappropriate disposal of straw results in wasting of resources, and also causes a serious ecological crisis. Screening microorganisms with the capacity to degrade straw and understanding their mechanism of action is an efficient approach to solve such problems. For this purpose, our research group isolated three actinomycete strains with efficient lignocellulose degradation ability from soil in the cold region of China: Streptomyces sp. G1T, Streptomyces sp. G2T and Streptomyces sp. G3T. Their microbial properties and taxonomic status were assessed to improve our understanding of these strains. The three strains showed typical characteristics of the genus Streptomyces, and likely represent three different species. Genome functional annotation indicated that most of their genes were related to functions like carbohydrate transport and metabolism. In addition, a similar phenomenon also appeared in the COG and CAZyme analyses, with a large number of genes encoding carbohydrate-related hydrolases, such as cellulase, glycosidase and endoglucanase, which could effectively destroy the structure of lignocellulose in corn straw. This unambiguously demonstrated the potential of the three microorganisms to hydrolyze macromolecular polysaccharides at the molecular level. In addition, in the straw-returning test, the decomposing consortium composed of the three Streptomyces isolates (G123) effectively destroyed the recalcitrant bonds between the various components of straw, and significantly reduced the content of active components in corn straw. Furthermore, microbial diversity analysis indicated that the relative abundance of Proteobacteria, reportedly associated with soil antibiotic resistance and antibiotic degradation, was significantly improved with straw returning at both tested time points. The microbial diversity of each treatment was also dramatically changed by supplementing with G123. Taken together, G123 has important biological potential and should be further studied, which will provide new insights and strategies for appropriate treatment of corn straw.

Application of Aspergillus niger in Practical Biotechnology of Industrial Recovery of Potato Starch By-Products and Its Flocculation Characteristics.

This study developed a practical recovery for potato starch by-products by A. niger and applied it on a plant scale to completely solve the pollution problems. Soughing to evaluate the effect of A. niger applied towards the production of by-products recycling and analyze the composition and characteristics of flocculating substances (FS) by A. niger and advance a possible flocculation mechanism for by-product conversion. After fermentation, the chemical oxygen demand (COD) removal rate, and the conversion rates of cellulose, hemicellulose, pectin, and proteins were 58.85%, 40.19%, 53.29%, 50.14%, and 37.09%, respectively. FS was predominantly composed of proteins (45.55%, w/w) and polysaccharides (28.07%, w/w), with two molecular weight distributions of 7.3792 × 106 Da and 1.7741 × 106 Da and temperature sensitivity. Flocculation was mainly through bridging and ionic bonding, furthermore, sweeping effects may occur during sediment. Flocculation was related to by-products conversion. However, due to severe pollution problems and resource waste, and deficiencies of existing recovery technologies, converting potato starch by-products via A. niger liquid fermentation merits significant consideration.

Microbispora cellulosiformans sp. nov., a novel actinomycete with cellulase activity isolated from soil in the cold region.

A novel cellulase-producing actinomycete strain Gxj-6T, isolated from soil in the cold region (Heihe city, Heilongjiang province, the northernmost part of China), subjected to a taxonomic study using a polyphasic approach. In the neighbour-joining phylogenetic tree based on 16S rRNA gene sequences, strain Gxj-6T fell within the clade comprising the type strains of species of the genus Microbispora. 16S rRNA gene sequence similarity studies exhibited that species Gxj-6T was most closely related to Microbispora bryophytorum NEAU-TX2-2T (99.45%), Microbispora fusca NEAU-HEGS1-5T (99.41%), Microbispora camponoti 2C-HV3T (99.31%) and Microbispora rosea subsp. rosea JCM 3006T (98.68%). Organism Gxj-6T contained MK-9(H2) as the predominant ubiquinone and C18:0 10-methyl as the major fatty acid. The major polar lipids of culture Gxj-6T were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol mannoside, three unidentified phospholipids, two unidentified glycolipids and two unidentified lipids. The DNA G+C content of strain Gxj-6T was 71.25 mol%. The morphological and chemotaxonomic properties of the strain are also consistent with those members of the genus Microbispora. Combinated with the lower DNA-DNA relatedness values, phenotypic properties, physiology and biochemistry distinctiveness with other recognized species strains, revealed that strain Gxj-6T is separated from other phylogenetically closely species of the genus Microbispora. Therefore, strain Gxj-6T is considered to represent a novel species of the genus Microbispora, for which the name Microbispora cellulosiformans sp. nov. is proposed. The type strain is Gxj-6T (= CGMCC 4.7605T = DSM 109712T).

Analysis of gene expression and histone modification between C4 and non-C4 homologous genes of PPDK and PCK in maize.

More efficient photosynthesis has allowed C4 plants to adapt to more diverse ecosystems (such as hot and arid conditions) than C3 plants. To better understand C4 photosynthesis, we investigated the expression patterns of C4 genes (C4PPDK and PCK1) and their non-C4 homologous genes (CyPPDK1, CyPPDK2, and PCK2) in the different organs of maize (Zea mays). Both C4 genes and non-C4 genes showed organ-dependent expression patterns. The mRNA levels of C4 genes were more abundant in leaf organ than in seeds at 25 days after pollination (DAP), while non-C4 genes were mainly expressed in developing seeds. Further, acetylation of histone H3 lysine 9 (H3K9ac) positively correlates with mRNA levels of C4 genes (C4PPDK and PCK1) in roots, stems, leaves, and seeds at 25 DAP, acetylation of histone H4 lysine 5 (H4K5ac) in the promoter regions of both C4 (C4PPDK and PCK1) and non-C4 genes (CyPPDK1, CyPPDK2, and PCK2) correlated well with their transcripts abundance in stems. In photosynthetic organs (stems and leaves), dimethylation of histone H3 lysine 9 (H3K9me2) negatively correlated with mRNA levels of both C4 and non-C4 genes. Taken together, our data suggest that histone modification was involved in the transcription regulation of both C4 genes and non-C4 genes, which might provide a clue of the functional evolution of C4 genes.

[Responses of spring corn growth and yield in a cold area of China to field warming at nighttime during pre-anthesis stage].

By using the facility for increasing free air temperature, a field experiment was conducted in a cold area of Northeast China to study the responses of the growth and yield of rain-fed spring corn to the field warming at nighttime during pre-anthesis stage. Under the field warming at nighttime, the nighttime temperature in 0-10 cm soil layer increased by 1.7 degrees C, and the soil moisture content had a slight decrease. Nighttime warming advanced the spring corn phenophases obviously, shorted the pre-anthesis phase by 1 day, and prolonged the post-anthesis phase by 1 day. Nighttime warming also promoted the corn seedlings growth and the root length. Comparing with those in un-warming treatment, green leaf area and three-ear-leave area in nighttime warming treatment increased by 13.5% and 14.6%, and the aboveground biomass, grain yield, and 100-grain mass increased significantly by 8.2%, 9.3%, and 7.1%, respectively. It was suggested that the climate warming (especially the nighttime warming) in Northeast China could improve spring corn growth, and directly affect the corn yield.