Genome-wide identification of PME genes, evolution and expression analyses in soybean (Glycine max L.).

BACKGROUND: Pectin methylesterase (PME) is one of pectin-modifying enzyme that affects the pectin homeostasis in cell wall and regulates plant growth and diverse biological processes. The PME genes have been well explored and characterized in different plants. Nevertheless, systematic research on the soybean (Glycine max L.) PME genes remain lacking. RESULTS: We identified 127 Glycine max PME genes (GmPME) from the soybean Wm82.a2.v1 genome, which unevenly distributed on 20 soybean chromosomes. Phylogenetic analysis classified the GmPME genes into four clades (Group I, Group II, Group III and Group IV). GmPME gene members in the same clades displayed similar gene structures and motif patterns. The gene family expansion analysis demonstrated that segmental duplication was the major driving force to acquire novel GmPME genes compared to the tandem duplication events. Further synteny and evolution analyses showed that the GmPME gene family experienced strong purifying selective pressures during evolution. The cis-element analyses together with the expression patterns of the GmPME genes in various tissues suggested that the GmPME genes broadly participate in distinct biological processes and regulate soybean developments. Importantly, based on the transcriptome data and quantitative RT-PCR validations, we examined the potential roles of the GmPME genes in regulating soybean flower bud development and seed germination. CONCLUSION: In conclusion, we provided a comprehensive characterization of the PME genes in soybean, and our work laid a foundation for the functional study of GmPME genes in the future.

Directed modification of a ruminal cellulase gene (CMC-1) from a metagenomic library isolated from Yunnan gayal (Bos frontalis).

Gayal (Bos frontalis) of the Yunnan region is well adapted to harsh environmental conditions. Its diet consists predominantly of bamboo, reeds, and woody plants, suggesting that the rumen of this species contains many fiber-degrading bacteria and cellulases. The aim of this study was to identify and modify specific cellulases found in the gayal rumen. In the present study, a directed evolution strategy of error-prone PCR was employed to improve the activity or optimal temperature of a cellulase gene (CMC-1) isolated from gayal rumen. The CMC-1 gene was heterologously expressed in Escherichia coli (E. coli) BL21, and the recombinant CMC-1 protein hydrolyzed carboxyl methyl cellulose (CMC) with an optimal activity at pH 5.0 and 50 °C. A library of mutated ruminal CMC-1 genes was constructed and a mutant EP-15 gene was identified. Sequencing analysis revealed that EP-15 and CMC-1 belonged to the glycosyl hydrolase family 5 (GHF5) and had the highest homology to a cellulase (Accession No. WP_083429257.1) from Prevotellaceae bacterium, HUN156. There were similar predicted GH5 domains in EP-15 and CMC-1. The EP-15 gene was heterologously expressed and exhibited cellulase activity in E. coli BL21 at pH 5.0, but the optimum temperature for its activity was reduced from that of CMC-1 (50 °C) to 45 °C, which was closer to the physiological temperature of the rumen (40 °C). The cellulase activity of EP-15 was about two times higher than CMC-1 at 45 °C or PH 5.0, and also was more stable in response to temperature and pH changes compared to CMC-1. This study successfully isolated and modified a ruminal cellulase gene from metagenomics library of Yunnan gayal. Our findings may obtain a useful cellulase in future applications and present the first evidence of modified cellulases in the gayal rumen.

Influence of Photoactive Layer Structure on Device Performance of Poly(2-methoxy-5-(2-ethylhexyloxy)- 1,4-phenylene vinylene)-CuInS2/ZnO Solar Cells.

This paper reported ternary MEH-PPV-CuInS2/ZnO solar cells, which were fabricated with the mixture of poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene) (MEH-PPV) and CuInS2 quantum dots (QDs) as photovoltaic layer and ZnO nanorod arrays (ZnO-NAs) as electron acceptor. The effects of photoactive layer structure (e.g., the change of spinning rate, thermal annealing temperature, annealing order and annealing method) on device performance are observed, and devices are measured by steady current-voltage (J-V) curve under the monochromic illumination at 470 nm. Results showed that the spinning rate of photoactive layer at 2000 rpm obtained the optimum thickness, moreover, solvent annealing firstly then the deposition of the positive electrode, finally thermal annealing at 140 degrees C contributing to the better reorganization for polymer and CuInS2 QDs to form the more stable phase-segregated state in the photovoltaic layer in the MEH-PPV-CuInS2/ZnO-NAs solar cells, obtaining the maximum power conversion efficiency of 2.54% under the monochromic illumination at 470 nm.