Hidden diversity and potential ecological function of phosphorus acquisition genes in widespread terrestrial bacteriophages.

Phosphorus (P) limitation of ecosystem processes is widespread in terrestrial habitats. While a few auxiliary metabolic genes (AMGs) in bacteriophages from aquatic habitats are reported to have the potential to enhance P-acquisition ability of their hosts, little is known about the diversity and potential ecological function of P-acquisition genes encoded by terrestrial bacteriophages. Here, we analyze 333 soil metagenomes from five terrestrial habitat types across China and identify 75 viral operational taxonomic units (vOTUs) that encode 105 P-acquisition AMGs. These AMGs span 17 distinct functional genes involved in four primary processes of microbial P-acquisition. Among them, over 60% (11/17) have not been reported previously. We experimentally verify in-vitro enzymatic activities of two pyrophosphatases and one alkaline phosphatase encoded by P-acquisition vOTUs. Thirty-six percent of the 75 P-acquisition vOTUs are detectable in a published global topsoil metagenome dataset. Further analyses reveal that, under certain circumstances, the identified P-acquisition AMGs have a greater influence on soil P availability and are more dominant in soil metatranscriptomes than their corresponding bacterial genes. Overall, our results reinforce the necessity of incorporating viral contributions into biogeochemical P cycling.

[Effects of drought stress on C, N and P stoichiometry of Ulmus pumila seedlings in Horqin sandy land, China.] / å¹²æ—±èƒè¿«å¯¹ç§‘å°”æ²æ²™åœ°æ¦†æ ‘å¹¼è‹—C、N、P化学计量特征的影响.

To understand the effects of drought stress on C, N and P stoichiometry in different organs of Ulmus pumila, U. pumila seedlings were grown under suitable water level, mild, moderate and serious water stress treatment, i.e., 80%, 65%, 50% and 35% of field water holding capacity. The results showed that drought stress increased C content in leaves, stems, coarse and fine roots, N content in leaves, stems and coarse roots, and P content in fine roots, but decreased P content in leaves, stems and coarse roots. Moreover, C:N in leaves and stems decreased, while C:P and N:P in leaves, stems and coarse roots increased and in fine roots reduced in response to drought stresses. There were significant correlations of C content among different organs, while N content was not correlated with P content in all organs. Soil water content was negatively related to C content in all organs, N content in leaves, P content and C:N in fine roots, C:P and N:P in leaves, stems and coarse roots. There were positive relationships between the soil water content and N content in fine roots, P content in leaves, stems and coarse roots, C:P and N:P in fine roots. These findings indicated that the absorption and upward translocation of N and P of U. pumila seedlings were influe-nced by drought stress. Nitrogen limitation for the growth of U. pumila seedlings was found. With the increases of drought stress, however, P limitation was gradually enhanced.

[Effect of celastrol on Akt signaling pathway and apoptosis of leukemic K562 cell line].

OBJECTIVE: To research the effect and route of celastrol on Akt signaling pathway of human leukemia cell line K562 apoptosis. METHODS: The activities of K562 proliferation cells were detected by MTT assay; cell apoptosis was detected by Hoechst 33258 staining assay, DNA fragmentation assay, and Annexin V/PI double-labeled cytometry; the expression and phosphorylation level of Caspase family members and AKT signaling pathway related proteins were determined by Western blot before and after celastrol treatment, and further the effect of AKT signaling pathway on celastrol-induced-apoptosis was analyzed. RESULTS: K562 cell proliferation was inhibited by celastrol in a time- and dose-dependent manner, with the IC50 value for 24 h of (2.15 +/- 0.11) micromol/L. Celastrol induced K562 cells apoptosis in a dose-dependent manner, apparent DNA fragmentation and typical apoptotic morphological changes, and accompanied Caspase-3, 8 activation in the apoptosis process were shown after cells were treated with 2.0 micromol/L celastrol for 24 h. And the celastrol induced apoptosis could be blocked by 50 micromol/L z-VAD-fmk (caspase inhibitor), but augmented by 25 micromol/L WORT (PI3K-Akt inhibitor). Moreover, Celastrol decreased the expressions of p-Akt, survivin and Bcl-2 in the Akt signaling pathway. CONCLUSIONS: Celastrol inhibited the proliferation of K562 cells and induced cell apoptosis by way of activating caspase cascade. The decreased level of Akt phosphorylation during celastrol-induced-apoptosis process suggested that celastrol acted synergistically with PI3K-Akt inhibitors in K562 cell apoptosis inducing.