Biochar has been shown to influence soil microbial communities in terms of their abundance and diversity.  However, the relationship among microbial abundance, structure and C metabolic traits is not well studied under biochar application.  Here it was hypothesized that the addition of biochar with intrinsic properties (i.e., porous structure) could affect the proliferation of culturable microbes and the genetic structure of soil bacterial communities.  In the meantime, the presence of available organic carbon in biochar may influence the C utilization capacities of microbial community in Biolog Eco-plates.  A pot experiment was conducted with differenct biochar application (BC) rates: control (0 t ha^–1), BC1 (20 t ha^–1) and BC2 (40 t ha^–1).  Culturable microorganisms were enumerated via the plate counting method.  Bacterial diversity was examined using denaturing gradient gel electrophoresis (DGGE).  Microbial capacity in using C sources was assessed using Biolog Eco-plates.  The addition of biochar stimulated the growth of actinomyces and bacteria, especially the ammonifying bacteria and azotobacteria, but had no significant effect on fungi proliferation.  The phylogenetic distribution of the operational taxonomic units could be divided into the following groups with the biochar addition: Firmicutes, Acidobacteria, Gemmatimonadetes, Actinobacteria, Cyanobacteria and α-, β-, γ- and δ-Proteobacteria (average similarity >95%).  Biochar application had a higher capacity utilization for L-asparagine, Tween 80, D-mannitol, L-serine, γ-hydroxybutyric acid, N-acetyl-D-glucosamine, glycogen, itaconic acid, glycyl-L-glutamic acid, α-ketobutyricacid and putrescine, whereas it had received decreased capacities in using the other 20 carbon sources in Biolog Eco-plates.  Redundancy analysis (RDA) revealed that the physico-chemical properties, indices of bacterial diversity, and C metabolic traits were positively correlated with the appearance of novel sequences under BC2 treatment.  Our study indicates that the addition of biochar can increase culturable microbial abundance and shift bacterial genetic structure without enhancing their capacities in utilizing C sources in Biolog Eco-plates, which could be associated with the porous structure and nutrients from biochar.

In legume plants, uricase gene (Nodulin-35) plays a positive role in metabolism of ureide and amide compounds in symbiotic nitrogen-fixing in the nodules. In this study, a pot experiment was performed to examine the effects of ammonium application on the transcription of MsU2 gene and distribution of major nitrogen compounds in alfalfa Medicago sativa. Data showed that alfalfa plant has a significant difference in contents of nitrogen compounds in xylem saps compared with soybean plant, and belongs to typical amide type legume plants with little ureide accumulation, and the accumulation of asparagines and ureide in the tissues of alfalfa is mainly gathered in the nodules. Northern blotting showed that excessive ammonium significantly inhibited the transcription of MsU2 gene in the nodules and roots, and mRNA accumulation of MsU2 gene in the plants exposed to excessive ammonium decreased gradually with culture time extension, indicating that application of ammonium significantly inhibited the transcription of MsU2 gene in the alfalfa plants. Although the application of excessive ammonium increased the contents of amino acids in various tissues of alfalfa, the accumulation of allantoin reflecting the strength of uricase activity is remarkably reduced in the xylem saps, stems and nodules when alfalfa plants exposed to excessive ammonium, suggesting that application of excessive ammonium generated a negative effect on symbiosis fixing-nitrogen system due to inhibition of ammonium ion on uricase activity in the nodules of alfalfa. This result seems to imply that application of excessive ammonium in legume plants should not be proposed to avoid affecting the ability of fixing nitrogen in the nodules of legume plants, and reasonable dose of ammonium should be recommended to effectively utilize the fixed N from atmosphere in legume plant production.

Aquaporin proteins were demonstrated to play an important regulatory role in transporting water and other small molecules. To better understand physiological functions of aquaporins in extremophile plants, a novel ThPIP1 gene from the Thellungiella halophila was isolated and functionally characterized in the transgenic rice. Data showed that the ThPIP1 protein encoded 284 amino acids, and was identified to be located on the plasma membrane. The expression of ThPIP1 gene in the shoots and roots of T. halophila seedlings were induced by high salinity. The transgenic rice overexpressing ThPIP1 gene significantly increased plants tolerance to salt stress through the pathway regulating the osmotic potentials, accumulation of organic small molecules substances and the ratio of K+/Na+ in the plant cells. Moreover, split-ubiquitin yeast two-hybrid assay showed that ThPIP1 protein specifically interacted with ThPIP2 and a non-specific lipid-transfer protein 2, suggesting that ThPIP1 probably play a key role in responding to the reactions of multiple external stimulus and in participating in different physiological processes of plants exposed to salt stress.