Arbuscular mycorrhizal (AM) fungi can form symbiosis with 90% of the vascular plants and play important roles in ecosystem. To realize the AM fungal colonization at different succession stages in saline-alkali land and screen AM fungi species with great functions, roots and soil samples were collected from the three succession stages of Songnen saline-alkali grassland. The soil properties and AM fungal colonization were measured, and the fungus distributed extensively in three stages was annotated by sequencing for AML1/AML2 target, subsequently, maize was selected as the host to verify its colonization. The results showed that the soil properties improved with the succession of saline-alkali grassland. The plants’ communities of the three stages could be colonized by AM fungi, and the colonization rate of Leymus chinensis (the third stage) ranged from 66.67% to 100%, Puccinellia tenuiflora (the second stage) ranged from 50% to 80%, while the Suaeda glauca (the first stage) was only 35%–60%. Glomeraceae sp1 was identified as the dominant AM fungi species which occurred frequently in the succession of saline-alkali land with the isolation frequency, relative abundance, and importance value of 100%, 18.1%, and 59.1%, respectively. The colonization rate of Glomeraceae sp1 in maize ranged from 80% to 87% and similar mycorrhizal characteristics were detected in the roots of P. tenuiflora, S. glauca, and L. chinensis, indicating that Glomeraceae sp1 colonized the samples in the field. The correlation matrix indicated that colonization rate, colonization intensity, and vesicle abundance were closely related to soil conditions most, and they were related significantly to all the soil properties except cellulase activity. Besides, redundancy analysis (RDA) showed that soil properties drove the changes of AM fungal colonization and sporulation. These results will provide theoretical support for realizing the relationship between AM fungal colonization and soil conditions, and also for the exploration of AM fungi species with great functions.
The gene dexYG encoding the dextransucrase from an industrial strain of Leuconostoc mesenteroides 0326 was isolated by PCR. The nucleotide sequence of the dexYG gene consists of an open reading frame (ORF) of 4,584 bp, coding for a 1,527 aa protein with a Mr of 170 kDa. The results were analysed by a BLAST similarity search of the GenBank database, which revealed the amino acid sequence was similiar to dsrD derived from L. mesenteroides Lcc4. The dexYG gene was subcloned into the plasmid pET28a(+) and was expressed in E. coli BL21 (DE3) by IPTG induction. The pH value was one of the main reasons which caused the degradation of enzyme activity in the later stage of induction. The highest activity was reached 36 U/ml after 5 h induction in medium at pH 6.0. Biotransformation yield of the enzyme reached 65% and the molecular weight of transformed dextran was more than 68 kDa in 2 h. 相似文献
Radiation‐induced intestinal injury (RIII) is a common complication after radiation therapy in patients with pelvic, abdominal, or retroperitoneal tumours. Recently, in the model of DSS (Dextran Sulfate Sodium Salt) ‐induced intestinal inflammatory injury, it has been found in the study that transgenic mice expressing hVDR in IEC (Intestinal Epithelial Cell) manifest highly anti‐injury properties in colitis, suggesting that activated VDR in the epithelial cells of intestine may inhibit colitis by protecting the mucosal epithelial barrier. In this study, we investigated the effect of the expression and regulation of VDR on the protection of RIII, and the radiosensitivity in vitro experiments, and explored the initial mechanism of VDR in regulating radiosensitivity of IEC. As a result, we found that the expression of VDR in intestinal tissues and cells in mice can be induced by ionizing radiation. VDR agonists are able to prolong the average survival time of mice after radiation and reduce the radiation‐induced intestinal injury. For lack of vitamin D, the radiosensitivity of intestinal epithelial cells in mice increased, which can be reduced by VDR activation. Ensuing VDR activation, the radiation‐induced intestinal stem cells damage is decreased, and the regeneration and differentiation of intestinal stem cells is promoted as well. Finally, on the basis of sequencing analysis, we validated and found that VDR may target the HIF/PDK1 pathway to mitigate RIII. We concluded that agonism or upregulation of VDR expression attenuates radiation‐induced intestinal damage in mice and promotes the repair of epithelial damage in intestinal stem cells. 相似文献
To understand arbuscular mycorrhizal (AM) fungi resources and develop AM fungal species in ornamental plants
with saline-alkaline tolerances, Iris lactea, which grows in the Songnen saline-alkaline grassland with a high ornamental value, was selected as the experimental material, and the colonization characteristics of its roots and the
AM fungal diversity in its rhizosphere were explored. The results of the observations and calculations of mycorrhizae from ten different samples showed that AM fungi colonized the roots of I. lactea and formed Arum-type
mycorrhizal structures. There was a significant correlation between soil spore density and pH value, while the
colonization rate showed a fluctuating trend with increasing pH values. The observed colonization intensities
were of Levels II (1%–10%) or III (11%–50%), and the vesicle abundances were of grades A2 or A3 among different sites. AM fungi produced a large number of mycelia and vesicles in the roots of I. lactea after colonization.
Thirty-seven species belonging to 15 genera of AM fungi were isolated from the rhizosphere of I. lactea and identified by morphological identification. Funneliformis and Glomus were the dominant genera, accounting for
21.79% and 20.85% of the total number, respectively. F. mosseae and Rhizophagus intraradices were isolated in
all samples with importance values of 58.62 and 51.19, respectively. These results are expected to provide a theoretical basis for the analysis of the salt tolerance mechanism of I. lactea and for the discovery, exploration and
further screening of AM fungal resources with salinity tolerances in saline-alkaline soils. 相似文献